HAM MER - The Geological Society of Trinidad and Tobago

HAM MER

G E O L O G I C A L S O C I E T Y O F T R I N I D A D A N D T O B A G O

Dec 2017The

Contents

ON THE COVER

Mayaro Formation, Trinidad and

Tobago 2014

.

Making History in

Guyana by Emily

Smith Llinas 47

02

11

34

.

Feature: Life and

career of veteran

geologist Mr. Fazal

'Faz' Hosein by

Stefon Harrypersad

UWI Prize Giving

Ceremony 2017

.

Tectonic Series

Part 4

Anthony

Ramlackhansingh

and Xavier Moonan

GSTT's Technical

Sessions and Social

Events

16

Deep Sea

Exploration for

Marine Mineral

Resources by Kevin

Tankoo

30

What is Operations

Geology? by Mark

Saunders

13

Is it normal? by

Shenille Samlal

39

Feature: Trinidad's

Changing coastlines by

Christopher Alexis

22

The Art of Making

Thin Sections by

Jonas Steele

44

P A G E 1 | T H E H A M M E R

On behalf of the executive of the Geological Society of

Trinidad and Tobago , we would like to wish you and

your family a prosperous and Happy New Year. As we

embark on this new chapter , the board is challenged to

find new and innovative ways to attract new

membership and encourage participation from our

existing members. Members can look forward to

another exciting year filled with informative technical

sessions , field trips to new localities and relevant short

courses.

The start of a new year is always a good time for goal

setting, both personally and professionally. Whether

your objective is to buy a new car , run a 5K , get that job

or promotion, I would like to challenge our

membership to include active participation in the GSTT

as one of your goals. It may seem like a tall order given

the amount of responsibility we have in our lives but

you are the heart and soul of this organisation and

without you, we cannot prosper. So participate , inspire ,

explore and expand your knowledge.

As geoscientists we are challenged everyday by the

mysteries of the earth and the best way to unravel

them is through sharing knowledge and collaborating

with each other. I dare you to stand out in your

organisation. Be the renegades who have the free spirit

dedicated to climbing mountains and walking through

river valleys collecting rocks , mapping wiggles and

drilling wells in search of answers.

I will leave you with a few words to inspire you in 2018

“It was during my enchanted days of travel that the

idea came to me , which, through the years, has come

into my thoughts again and again and always happily—

the idea that geology is the music of the earth.”

― Hans Cloos , Conversation with the Earth

Looking forward to seeing you at our first technical

session and throughout our varied events during the

year.

Ann Ramsook

GSTT President

P r e s i d e n t ' s N o t e

Ann Ramsook , GSTT President

L i f e a n d c a r e e r o f v e t e r a n g e o l o g i s t m r . f a z a l ' f a z ' h o s e i n

Stefon Harrypersad

g e o l o g i c a l s o c i e t y o f t r i n i d a d a n d t o b a g o

1 . H o w w o u l d y o u d e s c r i b e y o u r e a r l y , f o r m a t i v e y e a r s g r o w i n g u p i n T r i n i d a d ?

I grew up in east Trinidad in the town of Rio Claro where I was

exposed to the joys of living in the country side where my

activities included fishing, hunting and field trips , cricket, kite

flying and top spinning. My parents ’ family was involved in

agriculture and lumber industry and was well known in the

area and community life was good. My father was a shop

keeper.

2 . C a r e t o s h a r e w i t h u s a b i t a b o u t y o u r e d u c a t i o n a l a n d p r o f e s s i o n a l b a c k g r o u n d ?

I attended Rio Claro Presbyterian Primary school, then St.

Stephen’s college , Princes Town where I

completed “O” and “A” level studies in Chemistry, Geography and

Economics before leaving for London, England , UK where I

completed 1 year in Surveying at Regent Polytechnic. I started a

BSc. Degree in Geology at Kingston Polytechnic in 1969. I

graduated in 1972 with an Upper Second Class Honors Degree

from London University. I returned to Trinidad and started my

career as a geologist at Texaco Trinidad Inc. in September 1972 ,

Pointe a Pierre where I worked till 1985 before the company was

purchased by TRINTOC , the national oil company. I progressed

from 1972 to 1998 through positions of Development Geologist,

Senior Geologist, Senior Operations Geologist, Chief Geologist

and Geological Services Advisor. I resigned in 1998 to open my

own consultancy, International Geological Services Ltd which is

still active today after 19 years.

3 . h o b b i e s o r e x t r a - c u r r i c u l a r a c t i v i t i e s ?

My main sporting activity in my formative years was wind-ball cricket and fishing but while in England I

developed a passion for stamp collecting. I have obtained a valuable collection since then. I took up golf in

1981 while working for Texaco at Pointe a Pierre and reached my lowest handicap level of 10 at Pointe a Pierre

Golf Club. However , I gave up golf in 2003 after undergoing spinal surgery. I also played squash from 1972 to

keep me fit, sometimes with the Prime Minister Dr. Keith Rowley who was at that time working at the Seismic

Research Unit in St. Augustine.


Alaska 2013 Mendenhall Glacier meets sea



4 . W h y d i d y o u c h o o s e g e o l o g y a s a c a r e e r ?

I studied “A” level Geography at St. Stephen’s and was interested in geology which was not offered locally at

that time. I studied General Surveying for 1 year before attending Kingston Polytechnic , (later became

Kingston University), which was then one of the well- recognized institutions for Geology studies at that time.

I was also aware of the oil and gas activities in Trinidad at that time and wanted to pursue a career in the oil

industry

.


Rowan Gorilla 2011

F a z a l H o s e i n

I measure success for geologists by results in terms of production and the methodology used in the evaluation

process. There is no guarantee to find oil but risks can be avoided by following the proven guidelines for mitigating

failure.



5 . A s a y o u n g p r o f e s s i o n a l , w h a t w a s i t l i k e e n t e r i n g t h e w o r l d o f w o r k / i n d u s t r y ?

My undergraduate program at Kingston University prepared me well for work in the industry. Field trips in

England , Wales , Scotland and France gave me an excellent appreciation for the importance of rock outcrops

and the application to understanding of stratigraphy. My field mapping exercise required camping out on

the Scottish island of Mull for 12 weeks.

So , I was prepared 60% for the world of oil and gas industry. The other 40% required learning of oil and gas

activities such as well logging and interpretation and mapping of subsurface horizons. Texaco Trinidad was

the perfect place for learning and I made the most of the opportunity and following my early successes in

Oropuche field was given increasing areas of responsibility.

My career and learning path was greatly influenced by three American geologists. Bill Hughes taught me the

intricacies of development geology, Bob Peare shared his exploratory skills and Carl Henderson shared his

management skills. I also enjoyed my tenure as Geological Services Advisor for 3 years during which I

managed the renowned Geological Services Laboratory where I was exposed to the work of pioneers like Dr.

Hans Kugler in field mapping and Hans Bolli in paleontology. Thanks also to Mr. Wayne Bertrand who gave

me the opportunity to serve in higher levels of responsibility at Trintoc and Petrotrin.


6 . W h o a r e s o m e p e o p l e w h o i n s p i r e d y o u d u r i n g y o u r c a r e e r ?

Meeting with Energy Minister 2012



7 . W h a t a r e s o m e o f t h e h i g h l i g h t s o f y o u r c a r e e r a n d m a j o r p o r t f o l i o s y o u u n d e r t o o k ?

The major highlights of my career were the successes at Oropuche and Barrackpore fields on land , the east

coast offshore oil and gas condensate fields of Ibis, Pelican, Oilbird and Kiskadee , the west coast Iguana gas

field and lastly the Soldado Trinmar fields.

I started my career working in the Oropuche field where I was very successful in remapping the objective

Retrench sands and drilled many successful wells which resulted in an extension of the field to the south

west in the period 1972 - 1975. I then worked the intermediate thrust faulted section of the Herrera objectives

which I remapped in the Victoria block area of Barrackpore using the paleo zones developed by Hans Bolli. I

was very successful in adding significant new oil and gas reserves and extended the intermediate Herrera

trend further to the northeast.

I consider my contribution in the east coast offshore area to be significant and meaningful as it related to

the Trinidad economy. As the senior geologist with responsibilities for the East coast area from 1975 to 1980 , I

was directly involved in the discoveries at Ibis, Pelican, Oilbird and Kiskadee. I spent many weeks offshore as

operations geologist during drilling and logging operations. Later , I was also on the team with Texaco

geophysicist Bill McGinnis responsible for the west coast Trinidad discoveries of Iguana-1 and 2 wells. I also

worked on the East coast offshore Diamond and Emerald wells which were not commercial successes.

A key highlight of my career which prepared me for consultancy was my departure from Petrotrin in 1998. In

1998 , when I was Geological Services Advisor , senior persons were given the opportunity to take the golden

handshake package but I was declined because of Mr. Lisle Ramyard ’s position that he had no one to replace

me and my current position was not redundant. I decided to quit and become a consultant. Fortunately,

soon after quitting, I got an opportunity with Enron Oil and Gas to work in Houston for 6 months on the

Venezuelan block adjacent to Trinmar ’s acreage. My experience with Enron, a multinational company, gave

me valuable experience in 3D seismic interpretation and management, thanks to my manager , Michael

Rosen.

My work period at Enron which was extended to approximately 2 years prepared me for full consultancy

using new technology of computer workstations. I have worked for almost all the independent oil and gas

companies in Trinidad and made significant contributions in proposing many successful wells , especially at

Primera Oil and Gas Ltd.

8 . H o w d o y o u m e a s u r e s u c c e s s a s a g e o l o g i s t a n d w h a t w o u l d y o u c o n s i d e r a s y o u r m o s t s u c c e s s f u l m o m e n t i n t h e i n d u s t r y ?

I measure success for geologists by results in terms of production and the methodology used in the

evaluation process. There is no guarantee to find oil but risks can be avoided by following the proven

guidelines for mitigating failure. In my early times, mapping projects were done by individuals with some

technical supervision but evaluations were driven by individual research and technical assessment and not

subject to team vetting and management overview as it is today because of the manpower limitations. Apart

from my early successes in the Oropuche field , my most successful moment as a geologist employee was

looking at the log of BP552 which encountered almost 600 feet of gross pay sands. This well was the result of

months of work to unravel the thrust fault segments based on paleo. As a consultant in later years at Trinmar ,

thanks to Manager Mr. Egbert Waterman, I proposed several wells in Southwest Soldado , West Soldado and

South Main fields which I consider to be block busters. My work in southwest soldado resulted in the field

extension and the last well in south main produced at rates greater than 500 BOPD. As a geologist, my work

has resulted in finding more than 50 Million barrels of oil in addition to my contribution in gas and

condensate reserves offshore.



9 . C a n y o u h i g h l i g h t w h a t y o u m a y c o n s i d e r y o u r g r e a t e s t c h a l l e n g e a s a p r o f e s s i o n a l a n d t h e s t e p s y o u t o o k t o o v e r c o m e i t ?

When I was appointed Chief Geologist at Trinmar in 1989, I replaced Mr. Mahendra Nath who had done an

excellent job till then but only had available early vintage field 2D and 3D seismic only in Southwest Soldado.

I realized early that Trinmar will not progress if it did not catch up with technology and that to prepare for

the future in a way to better understand the geology of the fields and to maximize production from the

assets , the only way forward was to digitize all well data including logs and reports , acquire new 3D seismic

over the other west, main, north and east soldado fields and equip geologists and geophysicists with modern

computer workstations. I convinced Texaco , Trintoc and Trintopec to invest in a 500 Sq. Km 3D seismic

survey. I was strongly supported by my manager , Mr. Ken Birchwood who agreed with my approach. The

seismic was successfully acquired but parallel with that effort was the full digitization of all of Trinmar ’s data

and the acquisition of Landmark computer work stations. I received excellent support from geologist

Jennifer Chambers – Miguel in the well digitization project and from Dick Maywald , Texaco Geophysicist in

the 3D seismic processing. The challenge thereafter was the interpretation of the data and this was done by

a team of more than seventeen dedicated local Trinidadian and international Texaco professional geologists ,

geophysicists and technical assistants under my watch, which included locals Alysson Dupigny, Jenifer

James , Jeniffer Chambers- Miguel, Donald Charles , Leela Seegobin and Derek Smith who were well

supported by technical staff Vernon Dookie , Anil Ramroopsingh, Nazima Khan, Richard Hilaire. Ahylya

Ramlagan Sawh and Satish Neebar to mention a few. Training in this new technology was arranged and

everyone got on board. I was the facilitator. Thanks to the effort of our team, we achieved our goals and

objectives and prepared Trinmar for the future post 1995 period. The challenge was met head on and

successfully completed.


Faz Trinmar Consultancy 2006



GSTT Dinner 2007 : (Left to Right) Ms. Hazel Manning then Minister of Education and her late husband, former Prime Minister of the Republic of Trinidad and Tobago, the Honourable Patrick Manning a former geologist himself sharing a chat with Mr Fazal Hosein , then GSTT President.


1 0 . Y o u a r e a l o n g s t a n d i n g m e m b e r o f G S T T , s e r v i n g a s P r e s i d e n t o n n u m e r o u so c c a s i o n s a n d i n o t h e r p o r t f o l i o s , w h a t c o n v i n c e d y o u t o c o n t r i b u t e t o t h es o c i e t y ?

While working at Trinmar as a consultant in 2003, I realized that the society was not achieving

what it set out to be and the members were losing interest. Apart from the yearly joint conference

with the Energy Chamber and the yearly career sessions, the society needed a boost. In my early

days our bosses believed it was mandatory to attend GSTT meetings but it had become

disappointing by 2003. Membership attendance was low and student participation was very poor

in 2003. I wanted a change and believed that as President I could make those changes.

PAGE 7 | THE HAMMER

1 1 . W h a t w o u l d y o u c o n s i d e r s o m e o f y o u r b e s t c o n t r i b u t i o n s t o t h e G S T T ?

I was president of the GSTT in 2003 and in 2007 and was a director for many years. After much

personal time to compile the data , I introduced the first non-government GSTT Lease map which

for the first time showed all the blocks under license from the Government . This map was a big hit

with all stakeholders in the oil and gas industry. In addition , I introduced the new motto for GSTT

“working with you for all of us”, GSTT lapel pin , the executive lapel pin , the first GSTT Calendar, the

GSTT Photo Competition , the first GSTT Golf Tournament , the first GSTT Squash Tournament , a new

digital GSTT Logo, chaired one of the most successful GSTT Energy conferences ever in 2007 and

was a Co- Convener of the AAPG - Hedberg 2006 Conference in Trinidad . I believe that I have

made a significant contribution to GSTT.



1 3 . A n y a d v i c e f o r t h e G S T T a n d w h a t w o u l d y o u l i k e t o s e e c h a n g e d o r i m p r o v e d ?

GSTT is doing fine at this time. However , the strength of GSTT is with its membership. There is a lack of

participation by senior members who need to share experiences with junior professionals.

Recently, I met a geologist who was very excited to know he had met me , the person who wrote the paper

on Intermediate Herrera evaluation in 1985. More of this kind of interaction needs to occur.

1 2 . H a v e y o u s e e n t h e s o c i e t y g r o w a n d b e c o m e m o r e p r o m i n e n t i n t h e l o c a l e c o n o m y ?

Yes , the society has done exceedingly well in recent times, growing in stature due the efforts of members

and the respective presidents. Student participation has increased substantially and the GSTT Energy

conference was well supported and very successful in attracting much international participation. I think

more needs to be done by GSTT to seek recognition by Government and to be consulted on important

matters of the oil industry.

1 4 . W i t h y o u r e x p e r i e n c e , w o u l d y o u o f f e r s o m e a d v i c e t o p r o f e s s i o n a l s w h o f i n d t h e m s e l v e s d i s e n c h a n t e d d u r i n g i n t h e s e t o u g h t i m e s ?

Disenchantment comes when there is no mentorship and when you are placed in a cubby-hole with no cross

training. Always give more than 100%. The worst case scenario is when your supervisor is not able to help you

and unwilling to bring in expert help for fear of looking incompetent. When that happens, leave the job or

educate yourself on your time. Older professionals (retired and active) have a lot more to help other than in

technical issues. Do not be afraid to tell management that you need outside help in matters related to

planning, seeing the bigger picture , project area evaluation steps, how to cope with the stress , decision

making and much more.

P A G E 8 T H E H A M M E R

Faz on Mt. McKinley (Mt.Denali)



1 5 . D o y o u h a v e a n y m a j o r r e g r e t s a c r o s s y o u r e n t i r e c a r e e r ?

I have no regrets. I have made bold decisions in the past which worked in my favor. I turned down a Texaco

scholarship for an MSc Degree in Paleontology and quit Petrotrin at age 50 without a golden handshake.

Twenty years later I am still going strong. I am workstation computer literate unlike other persons in the

industry of my vintage.

1 6 . I f y o u c o u l d m a k e a f e w c o n c i s e s u g g e s t i o n s f o r T & T ' s g o v e r n m e n t w i t h r e s p e c t t o t h e e n e r g y s e c t o r , w h a t w o u l d t h e y b e ?

Government has not recognized the contribution of our past professionals who have contributed to the

country’s oil money earned in the past. Government should make a better effort to evaluate the assets held

by operators by doing their own evaluations and interpretations.

They should ensure that Petrotrin does not only engage personnel to monitor interests but ensure the

workforce is encouraged to perform, especially at this time when low oil production and low oil price

requires a greater effort. Not every geoscientist is an oil finder in mature fields.

1 7 . I t i s o f t e n s a i d a g e o l o g i s t n e v e r r e a l l y r e t i r e s , w h a t a r e y o u d o i n g t o k e e p y o u r s e l f o c c u p i e d ?

My track record as an oil finder is without question and backed by past results. In full recognition of the

politics at play in getting consultancy jobs in Trinidad , I made an early effort since 2003 to be involved in

Guyana ’s exploration efforts where I assisted companies who were interested in exploration for oil in onshore

blocks. Through networking and collaboration with other companies operating in the offshore environment, I

now have an excellent working knowledge of the Guyana basin. This knowledge prepared me for working

closely with the Guyana Geology and Mines Commission (GGMC) in recent times to help in their training

program of young professionals and students and also allowed me to be a resource provider for expert

professionals. I am as technically sound now as I was 15 years ago and still have many years left in me to

provide a valuable service to those needing it. My time is spent by research and planning for my next

assignment.

The GSTT salutes our former president

and longstanding member and sincerely

thank him for his sterling contributions

to our society.

We look forward to much more

interactions with him.

Pic : Faz Chief Geologist at Trinmar 1993

P A G E 9 T H E H A M M E R

C O N G R A T U L A T I O N S

UWI Prize Giving Ceremony RecipientsF A C U L T Y O F E N G I N E E R I N G 2 0 1 7 P R I Z E S A N D A W A R D S

24th October 2017

J O I N T H E G S T T ON A L L S O C I A L M E D I A P L A T F O RM S

LEVEL II BEST

ACADEMIC

PERFORMANCE

VARENDRA SAITH

details

LEVEL I BEST

ACADEMIC

PERFORMANCE

ARIANNE

BALIRAMSINGH

COLLECTED BY A

FRIEND IN THE

PICTURE

LEVEL III BEST

ACADEMIC

PERFORMANCE

CHARIS MUNGAL

W h a t i s O p e r a t i o n s g e o l o g y ?

Martin Saunders Training Manager Stag Geological Services Ltd.


O V e r v i e w

Operations Geology is a vital, but often not well understood , part of the exploitation of hydrocarbon reserves.

Within the Petroleum Geoscientist world many other disciplines (Exploration, Production, Reservoir and

Geophysics) have a higher profile and provide a more defined career path. How many students studying

geosciences at University dream of becoming an Operations Geologist? And yet, without them Exploration

and Appraisal drilling would not happen and , these days, the vast majority of development wells too.

Recent high profile incidents have resulted in the further , and very welcome , increase in standards for

Health, Safety and the Environment; Operations Geologists play a key role in both well planning and drilling

surveillance in helping to ensure that all these standards are met.

Until relatively recently most Operations Geology was provided by Consultants; because of the discontinuous

nature of drilling operations many Operators chose not to have permanent staff assigned to Operations

Geology roles and were content to hire in such expertise as required. The typical Consultant’s career path

was generally from a B.Sc. Geology degree , via mudlogging and Wellsite Geologist.

It so happened , of course , that in some large organisations some Consultants worked for months or even

years on a semi-permanent basis whilst in smaller companies the life of the Ops. Geologist was much more

ad-hoc. This arrangement suited both parties but, over recent years, with ever increasing costs , more

stringent HSSE requirements and changing demographics the lack of in-house Operations Geology

knowledge was beginning to be seen as a problem. The boom years of the 2000s meant that Consultants

could move positions more easily and the baby-boomers who joined the industry in the 1970s were

beginning to think about work-life balance and the opportunity to spend the kids ’ inheritance. The need for

in-house Operations Geology knowledge was becoming imperative , especially for the larger organisations,

and a career path for individuals was starting to become a reality.

Today then, Operations Geology is performed by both salaried staff and Consultants. But what is the role?

W h a t d o O p e r a t i o n s G e o l o g i s t s d o ?

This is tricky because one definition doesn’t suit all requirements. The nature of the Organisation and the

type of wells being drilled will require different skills and experiences from the individual(s). One general

definition might be :

The Operations Geologist is responsible for the planning, execution, and monitoring of the geological

operations of a well so that the well is properly evaluated and maximum geological and reservoir information

are obtained and distributed in the safest and most cost-effective manner.

The main requirements of the role cover :

• -Geological Interpretation

• -Communications

• -Bridging the gap between Geology and Geophysics; and drilling

• -Service Company Tender Preparation

• -Data Management

• -Well Planning

• -Formation pressure engineering from offset well data & while drilling

• -Geological Reports & Completion Log finalization and post well analysis

• -Partner well administration

The scope of services provided covers :

• Well Planning

• Drilling Surveillance

• Post Well Evaluation

P A G E 1 3 T H E H A M M E R




w e l l p l a n n i n g

The Operations Geologist will typically assist in well planning by helping produce the Geological Prognosis in

collaboration with other geological disciplines. This will include the nature of the reservoir rocks and the

overburden material to be drilled en-route. The drillers will need to know about formation tops, thicknesses

and the nature of the rocks they are required to drill. The hardness and mineralogy of the formations will

help in bit selection for example. Geological hazards which could lead to Drilling Inefficiency, Health and

Safety issues or Non-Productive Time also need to be addressed. Reactive formations, (clays and salt), lost

circulation cones (natural or induced), excessively hard formations , heterogeneous zones all need to be

identified so that the drillers cam choose the right tools and make the best operating decisions.

Procurement of site survey services might also fall under the Operations Geologist’s remit; for example in

offshore operations , the condition and strength of the sea floor and knowledge of shallow hazards such as

high-pressure gas and near-surface faults are critical in the initial planning stages.

A key part of well planning will be the Pore Pressure/Fracture Pressure Plot (PPFP). The Operations Geologist

will play a role in this; at the very least overseeing or liaising with Drillers or Pressure/Rock Mechanics

specialists. This process has to prove that the well can be drilled safely without any fluid influxes or major

losses that might lead to the loss of wellbore integrity.

P r o c u r e m e n t o f C o n t r a c t S e r v i c e s

Geological Data is obtained from many sources during and after drilling. Mudlogging services provide drill

cuttings and mud gas data ; LWD and Wireline services and petrophysics, testing and geosteering capabilities.

Coring, geochemistry and biostratigraphy services might also be required. A tendering process needs to be

established to identify, evaluate and procure the required services. Supply Chain Management and Human

Resources Departments are heavily involved in this process but the Operations Geologist is key in

establishing the technical requirements and overseeing the review process.

D r i l l i n g S u r v e i l l a n c e

During drilling the Operations Geologist has numerous tasks covering geological data collection and

distribution; management of service providers; and helping with geological interpretation. The vast amount

of drilling and geological data available in near real-time means that the Operations Geologist can be

involved in geological decision making at all times. Picking casing points and coring points , previously the

reserve of the Wellsite Geologist, are now within the Operations Geologist’s responsibility. Anything apart

from poking, prodding, sniffing and destroying (mechanically and chemically) the drill cuttings can now be

done remotely from the wellsite. Poking, prodding and sniffing the Driller is not normally recommended!

Managing Service Providers will potentially take up a good amount of time ; the logistics of getting people

and equipment to and from the wellsite in a timely manner is economically and operationally important as

well as ensuring the quality of their work.

Vast amounts of drilling and geological data are now obtained during and after drilling. Managing this data

and distributing it internally to different disciplines and also externally to partners and government agencies

is a mammoth task. Moreover storing this information so that it is readily available for future well planning

operations is vital and not something that has been done very well over the years.





P o s t W e l l E v a l u a t i o n

Following drilling geological data has to be finalized , stored and distributed and technical and financial

reviews of the all the Operations Geology needs to be done. There is no rest yet for the Ops. Geologist!

Lithology Logs are compiled by the Wellsite Geologist during drilling and include as much of the geological,

drilling and petrophysics data that is available. When drilling is completed this data is reviewed , edited and

refined. Formation Tops identified during drilling may be modified once final log interpretation has been

made or the results of biostratigraphy on cuttings or sidewall cores have been made. With all the final data

available Completion Logs are produced. This is normally the responsibility of the Operations Geologist

although the hands-on work may initially be done by other parties such as Junor Geologists or Technical

Assistants in-house or externally by Bureau Providers. The Operations Geologist can then sign off the final

documents.

Written geological reports accompany the strip logs; again these are initiated by the Wellsite Geologist and

completed by the Operations Geologist.

The Technical Review will evaluate the success of the geological operations. Was all the required data

obtained and if not, why not.

The financial review will document how well all the services were kept within budget.

c o n c l u s i o n sThe role of the Operations Geologist is complex and not always well understood. It requires Geological, Drilling and Petrophysics expertise , both practical and academic. It requires high levels of Communication and Diplomatic skills in liaising with different disciplines and at both ends of the Organisational Structure. It may require long working hours at very unsociable times although the ability to log in to real-time data whilst sitting on a beach sipping a (non-alcoholic) cocktail is not something that the babyboomers could have done forty years ago!

a b o u t t h e w r i t e r

Martin has been Training Manager with Stag since 1997

following almost 20 years service with Baker Hughes.

Following his B.Sc. Geology degree at the University of Wales ,

Aberystwyth in 1974 Martin went seeking fame and fortune

(neither of which quite materialized) as a Mudlogger. A stint in

the North Sea was followed by an 18-month posting to

Trinidad; the swaying of the palm trees and the odd bottle of

Carib (and Stag!) was replaced by the frozen wastes of the

Yukon. Offered respite behind a desk he took the role of

Training and Recruitment Manager for mudlogging operations

in the Europe/Africa/Middle East Region and , in the early

1990s , left Baker Hughes to pursue a career as an independent

training consultant. He has continued to provide and develop

technical training courses over the last 20 years and , in 2016,

four of Stag’s courses received full accreditation status from

the Geological Society of London.



L e t ' s G e t T e c hn i c a l ! T h e P e r l a S t o r y ,

F r om E x p l o r a t i o n t o P r odu c t i o n

Aaron Rampersad, a senior geophysicist employed with Repsol

presented our November technical talk. The talk was titled “The

Perla Story , From Exploration to Production” and based on work

done in the Perla Field during his 5 years stint in Venezuela. The

GSTT would like to thank Respol who sponsored this technical talk

for their continued support over the past year.

Special thanks to Repsol for sharing this impressive information

with our society!

T H E A G MT h e G e o l o g i c a l S o c i e t y o f T r i n i d a d a n d T o b a g o

E N D D E C E M B E R 2 0 1 7 I S S U E


B R E N T ' S F A R E W E L L

Professor Brent Wilson was givena warm send off at the AnnualAGM before he remigrated to hishome in Wales after 20+ years ofwork in Trinidad and Tobago. Picture below: Presented with aportrait done by Dr. KrishnaPersad and presented by Mr.Philip Farfan.

N E W E X E C U T I V E

Members of the new executivepose for a picture: LTR: HasleyVincent PhD., Sushma Chatelal,Ann Ramsook (President), LeonErriah, Vishram Rambaran,Gabriella Kokaram-Jagdeo,Stefon Harrypersad Not in Picture: Ms. Helena Inniss.

G S T T F A M I L Y

Above: members of the outgoing and incoming executive sharing a picture for memory lane. LTR: Gabriella Kokaram-Jagdeo, Reshma Maharaj, Sushma Chatelal, Ann Ramsook, Prof. Brent Wilson, Leon Erriah, Vishram Rambaran, Hasley Vincent PhD., Vishal Nagassar.

GSTT Social

special thanks to SHELL and BHP

for Sponsorship of our

Christmas Social

https : / /www .facebook .com /groups /THE .GSTT /

T H E G E O L O G I C A L S O C I E T Y

O F T R I N I D A D A N D T O B A G O

GSTT Christmas

Entrepreneurship talk

The GSTT and AAPGYPTT partnered with the Society of Petroleum Engineers Trinidad and Tobago

(SPETT) to host an Entrepreneurship talk given by Dr Krishna Persad. Dr Persad spoke about his

experiences as an entrepreneur and shared invaluable insights on what it takes to be successful in

business. The GSTT salutes our founder for his enthusiasm and contributions to our society and the

country and certainly look forward to more interactions with him.

San-Fernando Heritage Day

First Annual San-Fernando Heritage Day celebration at San-Fernando Hill. Mr Victor Young-On, the first

geophysicist in Trinidad and Tobago and a former president of the GSTT organised the GSTT 's boot with the

help of Keston Brown, our very enthusiastic and hard working GSTT Secretariat. On display were an

impressive rock collection, maps and geological cross-sections , plaques of notable geologists from early

petroleum industry, traditional mapping tools as navigators , stereoscopes, telescopes and a microscope as

well as posters. These fascinating and informative resources were organised by Mr Young-On from the

former Petroleum Historical Society and the GSTT also contributed with our resources. The GSTT salutes our

former president for his continued contributions to our society and we appreciate the work of our

Secretariat very much also

T r i n i d a d ’ s c h a n g i n g c o a s t l i n e s

Christopher Alexis , Research Officer ; Institute of Marine Affairs

G e o l o g i c a l S o c i e t y o f T r i n i d a d a n d T o b a g o

P A G E 2 2 | T H E H A M M E R

The shoreline monitoring component of the Coastal Conservation Project which commenced in 1988

provides valuable insight on the dynamic nature of Trinidad ’s coastlines. The scientific data is used to

inform government and other agencies with responsibility for formulating policies and plans on the

sustainable management of these areas. The project focuses on the 25 beaches and bays monitored ,

comprising 68 beach profiling stations. Each beach/bay has its unique geological characteristics.

The beaches and sediment are affected by the coastal processes (waves, winds , currents and tides).

These processes vary on a daily basis , and fluctuate seasonally. There are periods during the year that the

coastal processes change. During the winter and summer months of an annual cycle the beach

undergoes erosion and accretion respectively. The winter months are from November to April and the

summer months are from May to October. The winter months are characterized by larger waves,

generally with corresponding erosion (sediment loss) while the summer months are characterized by

smaller waves , generally with corresponding accretion (sediment gain).

Beaches are said to be in dynamic equilibrium if there is no net loss or net gain of sediment over an

annual cycle. Beaches accrete (become wider) when there is a net gain of sediment and erode (become

narrower) when there is a net loss of sediment.

The monitoring data from 2011-2015 reveal that most of the beaches and bays around Trinidad are

experiencing erosion, while a few beaches are in a state of dynamic equilibrium and even fewer

experiencing accretion.

Methods

Data Collection

Beach profiles , littoral processes and beach sediment grain size data were collected. Beach profiles are

cross sectional traces along a beach face that are perpendicular to the shoreline. Profiles were taken

along a transect that extends from a fixed point (the benchmark) in a stable area of the backshore to the

foreshore zone. Standard surveying techniques with a Sokkia survey level, survey tripod , measuring tape ,

survey staff and a compass were used for beach profiling. Beach profiles were conducted during low

tide conditions which allowed for the maximum transect distance to be captured. Some beach profiling

stations were referenced to Mean Sea Level (MSL) where the MSL elevations at these stations were

transferred from Land and Surveys tertiary benchmarks. For profiles not referenced to MSL, a local

datum, usually a value of 10 m, was assigned to the benchmark. Beach profile data were analyzed to

determine the changes in the horizontal beach width and beach volume and were presented in the form

of charts. Best fit lines were plotted to derive the underlying trend and both the regression line equation

and coefficient were stated.

Littoral processes data , such as wave height and breaker height, were collected to understand the

coastal processes operating at each monitoring station. Wind speed was collected using a digital

anemometer and measured in metres per second (m/s), while the direction was obtained with a Brunton

direct pointing compass. Wave height was measured with a 7.6 m extendable survey staff in the zone

immediately behind the breakers and was taken as the height between the crest and trough of a wave.

Breaker heights were measured in a similar method as the wave heights but, within the breaker zone.

Wave direction was measured from the shoreline with a Brunton direct pointing compass. Longshore

speed was measured by throwing a buoyant object into the water and measuring the movement of the

object for a time period of one minute. The longshore current speed was calculated in centimetres per

second (cm/s). The direction in which the object moved was obtained with a Brunton direct pointing

compass and then converted into a cardinal bearing and given as the longshore drift direction.





Beach sediment grain size data was collected to understand the composition of the sediment. Coarser

grainsize is indicative of higher wave energy on the beach. Sediment samples were collected from the

upper beach, mid-beach and lower beach at each beach monitoring station. Grain size analysis was

conducted using a method provided by Folk (1974). Wet samples were dried in 500 ml aluminum dishes

at 105oC for 24 hours. A random sample was then obtained for analysis using a sample splitter. Using an

analytical balance , approximately 120 g from the split random sample was weighed. The weighed

sample was transferred to a stack of sieves with a pan at the bottom of the stack. The stack was then

placed in a sieve shaker for at least 20 minutes to separate the sediment according to individual grain

sizes. Sediments were sieved using U.S Standard sieves at ½-phi unit intervals ranging from -4.0 phi (16

mm) to 4.0 phi (0.0625 mm). Sediment passing through the 4.0 phi sieve were collected in a pan and

were classified as mud. Each sieve fraction was then weighed using the analytical balance.

[Phi = -log2d , where d is diameter of the particle size in millimetres]

Results and Discussion

The majority of monitored beaches around Trinidad during 2011-2015 were experiencing erosion while a

few were in dynamic equilibrium and only a couple beaches showed accretion.

Erosion rates for each monitored site for the study period 2011-2015 is provided in Tables 1 to 4. Numbers

in red indicate net erosion, blue indicate net accretion and DE (dynamic equilibrium) indicates no net

sediment change.

















At Punta del Arenal, the beach profiles indicated growth of the berm toward the sea between 2011 and

2015 (Figure 2a). Long-term trends illustrated that beach width and beach volume increased between

2000 and 2015 (Figure 2b). The combination of southern littoral drift and well-sorted (Figure 2c), near

symmetrical, mesokurtic fine-skewed sediment (Figure 2d) indicated the accumulation of fine sediment

at this section of the bay, possibly as a result of the meeting of opposing currents in this area.

Guayaguayare Bay (East) – Net Erosion

At the eastern section of Guayaguayare Bay, the beach profiles indicated landward recession of the

scarp and a reduction in sediment volume between 2011 and 2015 (Figure 3a). Long-term trends

illustrated that beach width and beach volume decreased between 1996 and 2015 (Figure 3b). The

combination of western littoral drift and moderately well-sorted (Figure 3c), coarse-skewed and very

leptokurtic sediment (Figure 3d) highlighted the occurrence of erosion at this section of the bay. A

source of sediment may be from the nearby sandstone cliffs.




Tyrico Bay - Dynamic equilibrium

At the eastern section of Tyrico Bay, the beach profiles indicated a fluctuation in sediment along the

beach face between 2011 and 2015 (Figure 4a). Long-term trends illustrated that beach width and beach

volume generally revolved around a mean position between 2000 and 2015 (Figure 4b). The littoral drift

occurred to the west. Well-sorted (Figure 4c), near symmetrical and mesokurtic sediment (Figure 4d)

characterized the sediment at this section of the bay. This suggests a re-working of sediment within this

pocket bay.





Implications

In Small Island Developing States (SIDS) land is a finite resource which requires sustainable

management. The most valuable land in Trinidad are coastal, and they are experiencing significant

erosion (Figure 1) due to natural coastal processes and anthropogenic impacts. This vulnerability of the

coastline to erosion is expected to increase with impacts from climate change. Sea level rise , increased

frequency and intensity of storms and hurricanes , increased storm surge and increased precipitation

coupled with variable geological composition of the coastlines and the extraction of hydrocarbons and

freshwater , may result in accelerated erosion. For instance , the 2017 hurricane season registered ten

hurricanes within ten weeks and six were category three and higher. These storms cause high energy

waves to impact infrastructure , property and agricultural lands further inland. Most coastal development

should be constructed at a safe distance away (setback) from the impact of the coastal processes and

possible erosion. Erosion may be arrested by installing coastal protection structures.

Coastal protection may be applied using hard (revetment, groynes , breakwaters) or soft engineering

techniques (beach nourishment, mangrove planting). Revetments are found along Cocos Bay to protect

the Manzanilla-Mayaro road , groynes were installed at Columbus Bay to protect the Cocal Estate and

breakwaters were constructed in Guapo bay to protect oil pipelines (Figure 1). If coastal protection is

required , it is a costly undertaking which most citizens cannot afford. Defending a length of shoreline

may be in the millions of dollars and with coastal defence comes maintenance of these structures which

is also costly. It is always advisable to work with nature rather than against it such as with living

shorelines.

Some living shorelines may be found around Trinidad in the form of mangroves. These tree roots reduce

incoming wave energy to the coastline and result in the deposition of sediment allowing the mangrove

system to propagate seaward. In addition to mangroves , wrecks may be used as a foundation for

colonization by corals and eventually into a reef which acts as a breakwater to attenuate wave energy,

providing protection to the shoreline.

Trinidad ’s shorelines have seen an increase in the preference of hard techniques to provide protection

against coastal processes. These structures may sometimes exacerbate erosion if not constructed

properly, and can merely shifts the problem down drift of the shoreline. Scientific data on ocean

currents , depth and sediment movement is critical for designing appropriate coastal protection

measures.

Conclusion

Coastal communities need to know about the significant erosion occurring along the coasts, and that

this is expected to accelerate with impacts from climate change. The Institute of Marine Affairs has

taken a proactive role in addressing this matter by conducting scientific research and monitoring to

inform policies such as the Integrated Coastal Zone Policy that recommends building setback

legislation. IMA has been disseminating information on the state of our coasts through community

symposia and outreach activities , and has provided training on shoreline monitoring to coastal

communities. It is hoped that by building their capacity, they would be better able to adapt to the

unforeseeable future on our islands.

References

Alexis , Christopher , Amara Prevatt and Matthew Rahamut. 2017. Status of Beaches and Bays of Trinidad

2011-2015. IMA unpublished.

Folk, R.L. and Ward , W.C. (1957) Brazos River Bar : A Study of Significance of Grain Size Parameters.

Journal of Sedimentology and Petrology, 27, 3-26.

Deep-sea exploration for mineral resources has been of interest to the international community for quite

some time with recent developments driving a renewed focus on the recovery and processing of these

deposits. Over the last dec-ade advances in the geological and geophysical knowledge of the seabed

along with technological developments for the exploitation of these solid mineral resources promise

significant economic returns and valuable additions to the global resource base. Probable deep-sea

minerals may include metals such as manganese , nickel, copper , cobalt, plati-num, gold , silver , zinc , lead ,

tin, titanium, niobium etc. These minerals can be commercially recovered in polymetallic nodules ,

ferromanganese crusts , polymetallic sulphides as well as placer deposits and holds the focus of ongoing

explo-ration campaigns (Figure 1). The International Seabed Authority (ISA) has developed an extensive

framework govern-ing exploration activity of these marine mineral resources.

D e e p S e a E x p l o r a t i o n f o r M a r i n e

M i n e r a l R e s o u r c e s

Kevin Tankoo (UWI Mona Jamaica)


M a k i n g h i s t o r y


Polymetallic manganese nodules are one of the deep ocean mineral resources which have generated

interest from multiple contractors and continue to drive the exploration phase. Manganese nodules are

spherical or elliptical clumps of iron and manganese hydroxides on the seafloor. They are found at almost

all depths and latitudes in all the oceans of the world. It is estimated that these deposits cover

approximately 10 – 30 % of the deep ocean floor. Polymetallic manganese nodules are typically found half-

buried in comparatively flat deep-sea sediment at a depth of 4 ,000-6,000 meters (Figure 2a). The general

structure of these mineral resources is spherical or oval typically 2 cm to 15 cm in diameter (Figure 2b). The

main constituents are ferromanganese oxides , typically accompanied by a considerable amount of nickel,

copper , and cobalt. Manganese nodules were discovered in 1868 in the Arctic Ocean and since the 1960 ’s

developed countries have focused on the importance of manganese nodules as non-ferrous metal

resources.

Generalized global map showing the distribution of marine mineral deposits including polymetallic nodules, cobalt-rich ferromanganese crusts and polymetallic sulphides (Marine Minerals and Energy, 2010)

Another mineral resource which shows economic potential is cobalt-rich crusts or ferromanganese crusts.

These crusts are composed of ferromanganese oxides covering the bedrock with a thickness of several

mm to tens of cm. Cobalt-rich ferromanganese crusts cover the slope or top of seamounts like asphalt at

a depth of 800-2 ,400 meters (Figure 3a). The average cobalt content of this crust is three times as great

as manganese nodules , and it sometimes contain ore-grade platinum. They are typically distributed in

smaller areas compared to manganese nodules where thicker crusts are found on shoulders and summits

of seamounts. The surface structures are similar to manganese nodules and the noticeable layering

structure does not show cyclic change (Figure 3b). These deposits contain useful elements such as cobalt,

manganese , nickel, platinum etc. Polymetallic nodules were initially found at Kara Sea in the Arctic

Ocean off.






Siberia (1868); this was followed by the Challenger Expedition (1872-1876) which was a scientific cruise for

natural his-tory and chemistry by the Royal Society of London, England. The vessel travelled nearly 70 ,000

nm (130 ,000 km) sur-veying and exploring where 4 ,000 new marine animals were discovered (ISA, 2014).

Image of seafloor showing polymetallic nodule field as seen from ROV in the Indian Ocean at approximately 4500m deep (MNHN 2013); b) Polymetallic nodule sample retrieved from the ocean floor in south-west Pacific. Nodule contains nickel , copper and manganese.

Polymetallic sulphides were first noticed in 1948 during the Swedish Albatross oceanographic expedition

in the Red Sea. These marine resources were also later identified in 1979, on the East Pacific Rise near to

Baja California (Mexico), scientists exploring the ocean floor discovered chimney-like formations of dark

rock on sulphide mounds , spewing hot water and surrounded by relatively unknown animal species.

Since then, studies have shown that these black-smoker complexes are an outgrowth of the formation of

new oceanic crust through seafloor spreading as the tectonic plates underlying the earth’s surface

converge or move apart (ISA, 2014). Moreover , this activity is intimately associated with the generation of

metallic mineral deposits at the seafloor. At water depths up to 3 ,700 meters , hydrothermal fluids, having

seeped from the ocean into subterranean chambers where they are heated by the molten rock (magma)

beneath the crust, are discharged from the black smokers at temperatures up to 400° Celsius. As these

flu-ids mix with the cold surrounding seawater , metal sulphides in the water are precipitated onto the

chimneys and nearby seabed (Figure 4). These sulphides , including galena (lead), sphalerite (zinc) and

chalcopyrite (copper), accu-mulate at and just below the seafloor , where they form massive deposits that

can range from several thousands to about 100 million tons. High concentrations of base metals (copper ,

zinc , lead) and especially precious metals (gold , silver) in some of these massive sulphide deposits have

recently attracted the interest of the international mining industry. Many polymetallic sulphide deposits

are also found at sites that are no longer volcanically active (SPC 2013). The largest black smoker

discovered to date measure almost 45 metres high and occurred on the Juan de Fuca Ridge. Following

destruction, chimneys have been measured to grow as fast as 30 centimetres per day. The biggest chim-

neys are generally found on slow spreading ridges (Mid-Atlantic Ridge). On fast spreading ridges like the

East Pacific Rise , chimneys are rarely more than 15 metres high (SPC 2013).






Photograph of ferromanganese crust deposits on the seafloor at approximately at 2200 m possibly eroded from the flank of a seamount based on analysis of growth structure from cut section; b) Cut and polished section of ferromanganese crust retrieved by ROV from exploration campaign- multiple layers visible including the outer rough crust, detritus rich layer and substrate rock.

The geology behind the development of these mineral deposits is quite complex and requires detailed

sampling and analytical studies. Sampling and on-board analysis of mineral deposits is necessary in

mapping and evaluating contracted areas and developing targets. The geophysical acquisition

technology continues to be developed to include more advanced mapping tools, sonar equipment and

complex bathymetric surveys. The exploration of marine minerals is dependent on sound geological

investigations on the abundance and distribution of deposits, detailed high-resolution geophysical data

as well as advanced technologies in sampling and analysis. Overall deep-sea mineral exploration

campaigns have been plagued with multiple issues and draw-backs including cost of exploration,

environmental degradation concerns , effect on fisheries, limited mining technologies and even

complications with refining and dressing processes. Some countries are actively developing more

advanced seabed mining tools and testing programs which has shown good potential for the next phase

of this industry. A detailed insight into the exploration and sampling techniques from an ongoing

campaign within a contracted area will be provided in a future article.






Inactive polymetallic sulphide slot on the ocean floor of the Indian Ocean (BGR, 2015)

Kinematics : Contractional Deformation Island Arc/Continental CrusT

Timing Event: Plate Interaction

~37Ma-33Ma Late Eocene to Early Oligocene S.E directed oblique collision at the front of the Inflection

Zone of the overriding eastward advancing Caribbean Plate Oceanic Crust/ Island Arc/Accrectionary

Prism and underlying northward subducting ASACC with the CPOC/IA underpinning and wedging the

low grade metamorphosed PCP Caracas Involved Rocks, driving south-eastward shortening and

emplacement of the Cordillera de Costa (low-grade metamorphosed Caracas Group, also known as the

Coastal Ranges)/ Tinaco-Tinaquillo Basement Rocks/ Villa de Cura (Overriding Leading Edge CP

Accretionary Prism) Orogenic Belt and Guarico Foreland Fold & Thrust Belt unto the attenuated northern

margin of the SACC to the west with its associated ENE-NE trending Linked Guarico Foreland-CP Trench

Axis and Flexural Uplift/ Forebulge Arrival within the Maturin/ Plataforma Deltana/ SW Gulf-of-Paria Area

from NW to SE within EVB/GTA.

Tectonic Setting

Emplacement of the Orogenic Belt resulted in subsiding and drowning the Paleocene-Eocene Guarico

Forebulge and Oligocene Flexural Uplift/ Forebulge Arrival in the contiguous Maturin-Plataforma Deltana-

S.W. Gulf-of-Paria (Trinmar ’s Soldado Area) to sub-aerial erosion of Cretaceous passive margin rocks

(Temblador Group-Canoa and Tigre Formations) and possibly unconformably overlying Paleogene

Foreland deposits.

Continued overriding eastward advancing Leading Edge CPAP collided and became sutured or

incorporated with the north verging Proto-Caribbean Prism (PCP) overriding the northward dipping flank

of the Paleogene Folded Ridge and subsiding the restored Araya-Paria-Northern Ranges NW facing

passive margin outer shelfal to slope to basin floor deposits below the Extensionally Scarred Surface to

low grade metamorphism, i.e. the Late Jurassic Maraval banded limestones , Neocomian- Maracas

limestones and mid-slope turbidites, and Barremian-Aptian Cuche time-equivalent Laventille-Chancellor

and Toco-Tompire limestones, conglomerate , grits, sandstones and shales to low-grade marble , quartzite ,

phyllite , sercitic schists and slates. There is a general decrease in low-grade metamorphism from west to

east across the APNR uplift.

NOTES : From north to south along the Late Eocene-Early Oligocene Orogenic Belt

Restored Caracas north-west facing passive margin shelf-slope rocks contiguous with the time-equivalent

NW facing Late Jurassic to Early Cretaceous restored APNR deposits to the east, i.e. Maraval, Maracas , and

Cuche time-equivalent outer shelf to mid-slope sedimentary units.

Caracas Group also formed part of the north verging PCP setting ? or Folded Ridge due to Paleogene

southward Proto-Caribbean Shallow slab subduction collision.

T e c t o n i c S e r i e s 4 : G e o l o g i c a l

e v o l u t i o n o f t h e s o u t h e a s t e r n

C a r i b b e a n 3 7 M a – 3 3 M a

Anthony Ramlackansingh and Xavier Moonan



Tinaco-Tinaquillo crystalline igneous-metamorphic rocks found outcropping and juxtaposed to south of

the Caracas Group is part of the underlying E-M Jurassic syn-rift phase , i.e. Northern Margin ASACC that

was folded by northward ramping along the Paleogene southward Proto-Caribbean subducting slab

surface to become part of the Paleogene Folded Ridge which was subsequently incorporated as part of

the south-eastward shortening associated with the Late Eocene – Early Oligocene SE directed Caribbean

Plate oblique collision.

Juxtaposed to the south is the High P-T Villa de Cura blueschist rocks which were initially deposited into

a W to NW facing Forearc Accretionary Prism due to SE Pacific Oceanic Crust (Proto-Pacific Prism)

subduction beneath the west to NW margin of SACC during the Aptian to Albian, i.e. around the onset

Caribbean Plate Evolution out of primitive Pacific Oceanic Crust. Continued Cretaceous evolution of the

Leading Edge Caribbean Plate/IA/AP setting followed by its north eastward migration along the said SA

margin during the Paleocene resulted in suturing and incorporating the Villa de Cura High P-T

Accretionary material with the CP Accretionary Prism as the front of its SE Inflection Zone.Continued

eastward migration at the Leading Edge of the overriding eastward advancing Caribbean Plate between

North and South America during the Late-Mid-Eocene (~42Ma) resulted in the sutured CP AP/ Villa de

Cura AP setting overriding and subsiding the PCP or Folded Ridge – Caracas involved rocks to low grade

metamorphism at the front of its SE facing Inflection Zone. Continued eastward advancing CP , also

resulted in the sutured CPAP setting overriding the TInaco-Tinaquillo syn-rift basement rocks. Hence , its

outcrop position south of Late-Eocene –Early Oligocene (~27-33Ma) emplaced Cordillera de Costa –

Tinaco-Tinaquilla uplift and north of the Guarico foreland Fold & Thrust Belt. Emplacement of the Lara

Nappes to the west along the northern margin of ASACC during the Mid-Eocene (~46Ma) would have had

a similar tectonic history with High P-T blueschist minerals eroded from the sutured Western-Central

Cordilleras to the SW being transverse to NE axial parallel transported and deposited within the open NE

facing Proto-Pacific Forearc – Foredeep Basin becoming gradually accreted into the Prism setting.



C a r i b b e a n 3 7 M a – 3 3 M a




33 Ma reconstruction of the circum-Caribbean region, shown in the Indo Atlantic hot spot reference frame. North America-Caribbean plate boundary is taking on the form of today‘s boundary system. South America- Caribbean motion is ESE-directed, resulting in overthrusting of Caribbean terranes onto central and eastern Venezuela. Southeast dipping subduction beneath the northern Andes at the western South Caribbean Foldbelt was propagating eastward to the north of Maracaibo Block. (Pindell and Kennan, 2007)

Structural Styles/Geometries

Continued folding of the Paleogene amagmatic Backarc Folded Ridge with associated SE verging folding

and thrusting within the evolving Central Range/Nariva Fold & Thrust Belt due to continued Paleogene

southward Proto-Caribbean shallow slab subduction collision which was possibly stitched off at the End

Oligocene due to the arrival of the overriding eastward advancing Caribbean Plate Oceanic Crust/ Island

Arc system within the western reaches of the evolving EVB/GTA. However , some of these thrusted

anticlines would become remodified or destroyed due to subsequent Active Margin Tectonics. However

some remainpreserved in the subsurface within the Present Day Central Range/Nariva Fold & Thrust Belt

and its eastern offshore extensions, e.g. Emerald High, Kitchener. Crapaud , Zabocca , etc. Subsequent

Active Margin Tectonic Events include the Miocene SE directed Caribbean Plate oblique collision and

Pliocene/Pleistocene Transpressional Deformation along the onshore Central Range and its eastern

offshore extensions.

Sedimentation/Reservoirs

Late Eocene to Early Oligocene broad wavelength low amplitude contiguous Maturin-Plataforma

Deltana- SW Gulf-of-Paria Forebulge exposed Maastrichtian Passive Margin Rocks , the Temblador Group

comprising of the Canea and EL Tigre continental-fluvial to shallow water clastic deposits and their

northward time-equivalent shelfal facies of the Scre and Guayata Groups comprising of the Barranquin

sandstones/limestones, El Cantil limestones , Chimeno transgressive shales and Quercual to San Juan

HSTs and TSTs systems. Possibly supply from unconformably overlying Paleogene Foreland Deposits? SW

to NE transverse to axial parallel transported sediments deposited within the open east facing residual

Paleogene synclinal lows of the evolving Central Range/Nariva Fold & Thrust Belt and its associated

Foreland Setting to the south within the subsiding amagmatic Proto-Caribbean Backarc Tectonic Setting.

It is questionable if any sediments were deposited within the evolving Caroni Piggyback Basin. However ,

sediments deposited comprised of proximal Late Eocene-Plaisance conglomerate in synclinal lows , San

Fernando silts within synclinal lows and Foreland Setting, and Early Oligocene-Angostura deepwater

turbidites within the open east facing Foreland Setting, i.e. eastern offshore of the evolving GTA encased

in Lower Cipero Shales (Paradise Marl).

Time-equivalent transgressive deltaic to shallow water deposits of La Pascua and Roblecito sedimentary

units gradually backstepping south-eastwards unto the drowning Paleogene Guarico Forebulge in EVB

towards the foothills of the Guyana Shield , with their time-equivalent deepwater facies within the Linked

Guarico Foreland Basin and distal equivalent of the Los Jabillos and Areo deepwater sedimentary units

within the ENE to NE Linked Guarico Foreland Basin-Caribbean Plate Trench Axis.

Sediment supplied from three margins , the Orogenic uplift to the north and west, the subsiding

Paleogene Forebulge , the exposed Oligocene Forebulge and the Reentrant which defines the mouth of

the re-oriented ENE prograding Proto-Orinoco River Deltaic System to the west. The neck of the

Reentrant being the headland position of the Linked Guarico Foreland Basin –CP Trench Axis to the west

or where the Foreland Setting merges with the Orogenic uplift.



C a r i b b e a n 3 7 M a – 3 3 M a




Depositional units within the evolving GTA unconformably overlie the Paleogene Backarc deposits with a

possible continued northward onlapping relationship onto the south dipping flank of the Folded

Extensionally Scarred Surface or northern flank of the subsiding Backarc Trough i.e. continued evolving

Caroni Piggyback Basin. Total sediment thicknesses range between a few tens of metres to 300 metres , a

function of the syntectonic evolution.

Depositional units within the evolving GTA unconformably overlie the Paleogene Backarc deposits with a

possible continued northward onlapping relationship onto the south dipping flank of the Folded

Extensionally Scarred Surface or northern flank of the subsiding Backarc Trough i.e. continued evolving

Caroni Piggyback Basin. Total sediment thicknesses range between a few tens of metres to 300 metres , a

function of the syntectonic evolution.



C a r i b b e a n 3 7 M a – 3 3 M a




Foredeep subsidence method of tracking Caribbean-South America displacement history, revised after Pindell et al. (1991). (a) Sediment accumulation curves for six autochthonous or parautochthonous locations along the margin from west to east. Typical passive margin subsidence histories persist until the times of Caribbean arrival , thereby loading the margin and initiating foredeep subsidence whose basal formations in each sub-basin are indicated in B. Foredeep onset clearly youngs eastward. However, the distance of foredeep advance along the margin is larger (c. 1500 km) than the true relative plate displacement (c. 1200 km) due to obliquity of convergence (indicated by the arrows in B). (b) Map of Caribbean advance relative to a palinspastically restored South America that is also rotated back to its Maastrichtian position relative to North America when convergence began, showing the times of forearc collision in Ma and the positions and names of formations recording foredeep subsidence (Pindell et al. 1998).

Charge Story/Trap

Recent commercial oil and gas discovery in Angostura sandstone reservoirs in thrusted anticlines located

in eastern offshore Trinidad that may have a Paleogene origin followed by Mid-Miocene SE directed

Caribbean Plate Oblique Collision and Pleistocene Transpressional Deformation. Thrusted anticlinal traps

are located sub-thrust to the eastern offshore extension of the Central Range. Field size is over 100MMBO

with about 5TCF of gas. Only discovery in these reservoirs todate within the GTA.

Commercial oil and gas accumulations within La Pascua and Roblecito transgressive shallow water

deltaic reservoirs unconformably overlying the drowning Paleogene Guarico Forebulge , as well as ,

underlying El Tigre Passive Margin shallow water deltaic reservoirs. Oil and gas sourced from Late

Cretaceous El Tigre Type II marine source rocks, as well as , Oligocene La Pascua Type I terrigenous source

rocks.

Traps include a combination of structural and stratigraphic pinchouts. Structural traps include Basement

involved upthrown fault blocks within the Forebulge due to flexural loading of the Orogenic Belt, as well

as , detached normal faults associated with the Transgressive depositional units.

Guarico fields include the Ruiz-Tucupido Trend , Los Mercedes Trend and Yucal-Placer Trend with 16o-46 o

API crude ; Ǿ 8-18%, K – 850md; Recovery Factor – 30-70% and Recoverable Reserves > 300MMBOE.



C a r i b b e a n 3 7 M a – 3 3 M a




From up on the hill, as I walked towards the shore , I saw a long stretch of rocky sea front, scattered with

boulders and pebbles. From this vantage point I could almost begin to discern smooth platforms of rock,

cracked and broken.

I s i t n o r m a l ?

Shenille Samlal, Ministry of Energy and Energy Affairs



Looking onto the shore (Image Source unknown)

After slipping and sliding in spitting rain to the main area , we came upon a large crack, with many

adjoining cracks culminating towards the centre in huge density of, guess what, more cracks.

Every time I visit field exposures like this, where one can observe results of the Earth’s forces at surface , it

strikes me how I have to rethink my bias that rocks are immeasurably strong. They, in reality, are

susceptible to the ever changeable processes of the Earth.

We had come to Kilve-East Quantoxhead , Somerset in the UK to collect quantitative data on these

lineations to test if theoretical fault growth models applied. We measured fault length, displacement and

locations with respect to a baseline.





The carbonate platforms described were deposited in the

Bristol Channel Basin in the Jurassic. During this time

most parts of Britain experienced basin-wide subsidence

resulting in the development of regional normal faults.

Normal faults generally occur in places where the

lithosphere is being stretched , creating planes of

weakness in the lithology. They extend in such a way

where the hanging wall block moves downwards with

respect to the footwall as shown in the diagram.

After this period of extension, compression due to the

Variscan convergence , in the Late Carboniferous, caused

these preexisting planes of weaknesses to change their

original kinematics from extension. This is called

structural inversion, changing the extensional normal

faults to compressional faults. Inversion was not directly

observed in these smaller scale faults measured but in

much larger faults along the shore.

So , what are fault models?

Like many things discussed in theory, fault models are

idealized. They were proposed using data which exhibit

little scatter , gathered in a relatively uniform lithologic

and tectonic settings that can aid in predicting fault

properties or behavior. There were developed for normal

faults to explain their evolution through time but usually

do not account for the complexity of all geological

scenarios.





If you are interested in learning more about these models these are some papers to read :

Peacock & Sanderson, 1991

Pollard & Segall, 1987

Walsh and Watterson,1987

Walsh, Nicol, & Childs , 2002

Walsh et al. , 2003

Schlagenhauf, 2008

Giba , Nicol, & Walsh, 2010

Burgmann et al.1994

Manzocchi, Walsh, & Nicol, 2006

Mouslopoulou et al. , 2009

Roche et al. , 2016

When the data collected was initially analyzed , the plots were horrendous and extremely difficult to

begin applying models. Kilve does not fulfill any of the aforementioned criteria for model application,

hence the results showed variation from the models. Does this mean that the models are incorrect?

Not necessarily.

The results were plotted and compared to existing growth models. Of particular interest were the

distance-displacement plots that highlighted the degree of interaction between adjacent faults.





The results being similar with the ones published by Peacock and Sanderson (1991) on data from the

same area. The man difference is the skew of the maxima to the left as opposed to the publication’s

definition of a centered maxima. This occurs as a result of interactions with adjacent faults. The

relocation of one segment to another occurred with the help of relay structures, relay ramps, whose

geometry relies on the differences between the displacements at adjacent segments.

Identification of relay ramps is critical in subsurface work. Using contemporary examples like those

being developed in Kilve give geoscientists an understanding of fault complexities while interpreting

seismic or performing basin reconstructions.

Relay ramps , when formed , represent ideal conduits for sediment flow and , when identified , can aid in

understanding sand fairways and sediment routes into a basin. This type of information is critical in

understanding the distribution and quality of sandstone reservoirs in the petroleum industry.

This linkage occurred on many scales from centimeter to metre length linkages demonstrating how the

entire fault zone propagated.

The faults were initially isolated , then started approaching each other , overlapping and linking, resulting

in the present day structure.

Each individual propagation and growth rate would be unique as it would have its own rock properties

that can change the shape of the fault. As well as some faults may interact with other segments,

affecting propagation rates. But other factors like erroneous readings , uncertain fault tip locations and

footwall erosion may have also caused deviation from the models.

Real life data are sometimes far from ideal which influences the application models. It is helpful to use

these existing models to understand the behavior of the faults, but deviance from said models does not

constitute that they do not entirely apply. Taking into consideration the conditions in which the

observed faulting occurs one can develop a unique modified model that is fit for purpose. Use of these

models are key in understanding normal fault evolution which is an integral process in the industry.

T H E A R T O F M A K I N G T H I N S E C T I O N S

Jonas Steele



Thin sections play a vital role in understanding key elements of a rock, particularly in the identification

of the rock forming miner-als present as well as the optical properties of said minerals in the sample.

This information can then be used to help determine the origin and evolution of the parent rock. So how

are these things made? After receiving a brief tour of the process from Mr. Rupert Green, the

department 's Technical Assistant, the process can be broken down into 5 simple steps :

1. cut the rock

2. polish the sample

3 . mount on a slide

4. grind down to appropriate size

5. voila!!

This piece intends to look at these steps in a bit more detail to give those unfamiliar with the process an

idea on how to make a thin section.

After bringing in your sample from the field , the first thing you need to do is to cut off a reasonable

piece from it. Usually the size of the cut depends on the size of slide you wish to mount it on, but an

average dimension of cubic 2cms is normally used. This is done using a cut-off saw. One must ensure

that the sample being used is fresh (unweathered) lest they want to examine nothing but clay minerals

in their thin section. Another point to note is that the name "cut-off saw" isn 't exactly the most fitting

considering that the blade technically doesn 't cut anything. Rather the diamond studded saw can be

more accurately said to abrade through the sample. The little limb above the blade as seen in figure 1,

keeps a slow but steady supply of water flowing to keep the contact between sample and blade fairly

lubricated.


Jonas Steele



So you have your cube. Your next step is to polish the surface of the sample and frost one side of the

glass slide. Silicon carbide , the gray powder seen in figure 2 , has a hardness of 9 on the Mohs Scale and

is used for both these steps. Some powder is added to a slab of glass, water is mixed in to act as a

lubricant, and sample and slide alike are rubbed in the mixture until the desired results are obtained.

Visceral is sometimes used in place of water in the event that the sample will react with the water if

used. The grade of silicon carbide used for this step is 600 , which is the finest available in the lab.

Polishing the sample gives a flat surface , while frosting one side of the glass is essentially done for the

opposite reason. The smooth surface of the sample along with the micro-scratches created on the

surface of the glass (frost) ensures that the adhesive will properly hold between the two.

Speaking of which, it 's now time to mount the sample onto the glass. A special type of adhesive is used;

a two-part mixture of Epoxy resin, and Epoxy hardener. Care is given when handling these agents as the

resin is corrosive , while the hardener is harmful, thus latex gloves are used to avoid any skin contact.

Using a burette , the blend between the 2 agents is done in a 2 :1 ratio of resin and hardener respectively.

The mixture first appears cloudy, but eventually turns clear upon stirring, the change also indicating that

the adhesive is ready for use.


Jonas Steele



The Epoxy is then applied to the smoothened end of the dried rock sample and the frosted side of the

glass , carefully ensuring that there are no air bubbles present. Air bubbles indicate that there is no

contact between sample and glass at that point, and thus can be a zone of weakness if left unchecked.

You might be wondering what 's so special about epoxy that requires us to go through all this trouble to

use it. Why not just dab some super glue on it right? Well, it turns out that epoxy not only has a longer

curing time , which makes it easier to work with, but more importantly, resin has the same refrac-tive

index as glass , which therefore allows light to travel through without it deviating - something you want

when studying these things under a petrographic microscope. After attaching the sample to the slide ,

they are then placed on a jig with a hot plate. This helps to reduce the amount of time the epoxy takes

to cure. The process is termed "hot-plate impregnation" and is often left overnight for good measure.

But what if you have sand , or some other unconsolidated sample that needs to be examined? For this

"vacuum impregnation" is done by adding some of the sand to small container , which itself is coated

with Releasing Agent, and some of the adhesive is poured into the container. This is then put in a

vacuum (see figure 3) and left to sit for 3 minutes, 3 times at 200Hg with an approximate three minute

break in-between. As the vacuum pulls the epoxy up and around the sample , the breaks allow for air

bubbles to escape. When this initial step is complete , the sample is again vacuumed for 30 minutes at

approximately 600Hg.

Now that the sample is successfully

mounted to the slide , all that 's left to do is

to trim it down to the needed size. You first

remove as much of the excess off the slide

as possible using the saw again, then the

real fun comes in. Using the different grades

of silicon carbide ; 240 (coarsest) 400

(medium) & 600 , you now have to grind

down the sample until it reaches

approximately 30 mi-crons or 0.03 mm

thick. There is a mechanical way of doing

this , as outlined in figure 4 , but

unfortunately for us students this is a

manual process, that can take from a few

hours , to several days depending on your

rock type. It 's a time consuming and

sometimes frustrating step - especially as

you risk rubbing away your section

completely, rendering the slide useless , as

has happened to sever-al of the final year

students working on their thesis - but it 's a

necessary one. At 30 microns, you can

practically see through the rock sample ,

which is the goal : for light rays to be able to

pass through it. When this step is complete ,

your section is ready for use.

AAPG chartered new territory last month with its first ever event held in Guyana, home to one of the

world’s most prospective deepwater basins.

“Deepwater Exploration of the Columbus & Guiana Basins ,” a Geosciences Technology Workshop (GTW),

convened 167 of the oil and gas industry’s top business leaders , academics and technical professionals

hailing from 17 countries throughout the Americas and Europe.

The GTW featured two days of presentations and discussions related to deepwater exploration stretching

from offshore Barbados and Trinidad to Guyana, Suriname and French Guiana.

Making History

Guyana’s Minister of Natural Resources Raphael Trotman and ExxonMobil Country Manager Rod Henson

inaugurated the event at opening reception held the evening before the workshop.

Min. Trotman recognized the significance of having an AAPG event in Georgetown.

“Guyana stands at the cusp of great transformation as we usher in this signal chapter in our history, one

that has already begun to transform the shape and texture of our society,” he said. “We therefore do not

make light of this first ever gathering of AAPG members on Guyanese soil; and upon this good and fertile

soil , I make the first step in declaring that it shall not be the last of its kind.”

Guyana’s oil exploration efforts started when 18th century explorers observed pitch seeps , while

abandoned offshore and onshore discoveries in the 1970s and 1980s showed potential.

The country joined the ranks of oil producing nations in 2015 following discoveries by ExxonMobil and

venture partners Hess and CNOCC Nexen in the Liza, Payara, Snoek and Turbot 1 wells.

Min. Trotman encouraged GTW participants to seek both geological and economic success thorough

continual learning, risk reduction and prudent investment.

“Just as the super-continents once connected us , it is also imperative that we stay connected in the

scientific community and among governments so that we can fully harness the full potential of our

geological basins. Forums such as this enable us to see the bigger, regional picture,” he said

Seeing the bigger picture

The workshop included three technical sessions : Regional Overview and Crustal Structure, Columbus Basin

Exploration , Guiana Basin Exploration and Future Exploration Potential. The poster session featured 12

presentations covering Demerara Plateau geology, tools and technologies to enhance E&P activities in the

region and strategies for engaging local communities.

The fourth session , Beyond the Wells : Working with Regulators and Communities , featured a panel

discussion covering corporate social responsibility, local content and community outreach in Guyana,

Suriname, Trinidad and Tobago and Barbados.

M a k i n g H i s t o r y i n G u y a n a

Emily Smith Llinás, AAPG Latin America & Caribbean Region Programs Manager

T H E G E O L O G I C A L S O C I E T Y O F T R I N I D A D A N D T O B A G O

PAGE 47| THE HAMMER

Panelist Dr. Jan Mangal, petroleum advisor to the President of Guyana, spoke candidly about how the

developing oil and gas industry can affect all aspects of the country’s socio-economic landscape, both

positively and negatively.

“Guyana has won a lottery,” he said. “Evidence from other countries is that this type of windfall is

usually squandered and does not benefit the people. This industry can only benefit the people of

Guyana if they become informed of the risks , if they insist on full transparency and hold their

representatives accountable, and if they get independent expert advice.”

Dr. Mangal urged companies seeking to do business in Guyana to understand the country and its

people.

“The challenges are rather daunting. There are vast sums of money at stake, and there are numerous

very savvy external players ,” he said. “Guyanese people (as opposed to Guyanese politicians) can be

quite skeptical of foreign investors. If they feel Guyana is being taken for a ride in comparison to other

countries , they will react.”

He invited his colleagues to help the country grow sustainably so that all stakeholders benefit.

“You have an opportunity to influence the direction of the industry in Guyana, and thereby Guyana’s

future,” he said. “Guyana can become a little Switzerland in the region , or can be another disappointing

oil state.”

Other panelists shared strategies for ensuring a positive way forward.

Mr. Anthony Paul , advisor to Guyana’s Ministry of Natural Resources , shared the Ministry’s policy

framework for local content and participation. The policy includes hiring Guyanese nationals as

employees or contractors as well as building capacity that enhances their ability to participate.

Ms. Kimberly Brasington , Guyana public and government affairs manager at ExxonMobil shared a

strategy for corporate citizenship , managing the impact of the company’s operations on Guyanese

economy, society and environment. She noted that 70 percent of the Esso Exploration and Guyana Ltd.

(Exxon ’s Georgetown affiliate) are Guyanese.

Giving back and looking forward

Event organizers and supporters sought to benefit not only those who attended, but also those who

live and work in Guyana.

AAPG provided two-for one workshop and short course registrations to employees from the Guyana

Geology and Mines Commission and free registration to staff from the Ministry of Natural Resources.

ExxonMobil sponsored registration for three Guyanese students , and Chevron sponsored registration

for a University of Guyana faculty member.

AAPG also organized a book drive and encouraged GTW participants to pack a textbook in their

suitcase. At the closing ceremony, General Chairs presented the books to the University of Guyana’s

geology department head and dean of technology.




PAGE 48| THE HAMMER

AAPG will continue to support future leaders through establishing a Student Chapter at the University of

Guyana and Young Professionals Chapter for recent graduates.

A dream come true

General Chair Mr. Xavier Moonan , AAPG Latin America and Caribbean Region education director and

University of the West Indies in St. Augustine professor, described GTW Guyana as a dream come true.

“Personally I have been very interested in the Guiana Basin since my undergrad years , where I followed

CGX 's activity very closely. An AAPG GTW held Trinidad in 2014 reaffirmed the potential of this basin with

the very positive signs from Repsol 's Jaguar well ,” he said.

Mr. Moonan shared his interest with Mr. Clyde Griffith, AAPG Latin America and Caribbean Region

delegate and team coordinator of the geoscience group at Staatsolie in Suriname.

“Xavier talked to me about his plans to have a GTW in Guyana or Suriname, because of the increased

activities (a lot of seismic surveys and wells) in the Guiana Basin ,” Griffith said. “After the Liza discovery it

was obvious that the GTW would be in Guyana,” he said.

Mr. Griffith attended the workshop , and subsequent 2-day short deep water reservoir characterization

with 10 Staatsolie colleagues , who took a 12-hour bus and ferry ride from Paramaribo to Georgetown.

“We came to gain knowledge and exposure that we are lacking at Staatsolie to understand the

architecture of the Guiana Basin ,” Griffith said, “We also wanted to the staff the opportunity to network

with other peers.”

Record attendance

Organizers were surprised by the number of attendees and participating companies.

“During early planning stages , we were expecting 40 maybe 50 attendees , representatives from some of

the key operating companies and maybe a few people who would be willing to share some exclusive

learnings from the basin ,” Moonan said. “We clearly exceeded our expectations , with almost 170

participants and 72 companies and highly technical presentations from the leading subsurface teams of

all regional players.”

Dr. Jim Pindell , director at Tectonic Analysis and workshop speaker said he was impressed how

participants collaborated throughout the event.

“What struck me was the feeling of a collective need to understand the basins , rather than a bunch of

competitive companies trying to glean whatever they could,” he said. “And it is interesting how the basic

tectonic evolution of the region has been known for 35 years , yet the economic potential has only been

exposed recently.”




PAGE 49| THE HAMMER

M a k i n g H i s t o r y i n G u y a n a Emily Smith Llinás , AAPG Latin America & Caribbean Region ProgramsManager

t h e g e o l o g i c a l s o c i e t y o f t r i n i d a d a n d t o b a g o

PAGE 50| THE HAMMER

W E M A D E I T !

THANKYOUT O A L L T H E C O N T R I B U T O R S A N D S P O N S O R S O F O U R M A G A Z I N E

KEEP ROCKING AND JOIN THE

GSTT NOW!

Date post:	25-Jan-2023
Category:	Documents
Upload:	khangminh22
View:	0 times
Download:	0 times

HAM MER - The Geological Society of Trinidad and Tobago

Documents