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CARBONATE ENVIRONMENTS
Brief Introduction
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Most modern carbonates are accumulating in warm, shallow waters.
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Basin margins typically start off as ramps
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
the ramp slope steepens with continued basin subsidence
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Shallow water carbonate sedimentation keeps pace with subsidence around basin margin but can not match the faster rates towards basin center. As water deepens, carbonate sedimentation rates are reduced. Shelf breakof slope results.
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
The break of slope is a site of high energy from incoming waves. This promotes carbonate precipitation for reef buildingor oolitic and other sand accumulation. Sheltered conditionsdevelop behind the reef or shoal (lagoon or protected shelf).
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Rimmed shelf edge or offshore carbonate banks develop in this way, adjacent to deep water areas.
Andros Island and Tongue of the Oceans
oolite shoals
shallow waterplatform carbonates
deep water
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Carbonate facies are divided by the shelf margin reef or carbonate sand shoals into back-reef and fore-reef/basin
fondoform clinoform undaform
(1969) GCAGS Transactions, v. 19, p. 11-22
J.L. Wilson (1975), "Carbonate Facies in Geologic History" Springer-Verlag
Wilson proposed 9 Standard Facies Belts
Carbonate Environments
• Subaerial exposure– karst
• caves, collapse breccias
– caliche
del Olmo, W.M., and M. Esteban (1983), AAPG Memoir 33, p.93
Esteban, M., and C.F. Klappa, (1983), AAPG Memoir 33, p. 6
Karst, China
Lechugilla Cave, New MexicoHamblin, W.K., and E.H. Christiansen (2001) “Earth’s Dynamic Systems” 9 th Ed., Prentice Hall
Labor Day 2000; 2000/24-22. Mile 490
Collapse breccias above zone of gypsum dissolution, Cretaceous Edwards Group, Texas
Caliche zone in modern soil profile, Texas.
from Moore, C.H., (2001), Carbonate Reservoirs, Porosity Evolution and Diagenesis in a Sequence Stratigraphic Framework. Elsevier. [book and CD]
Caliche glaebules (“pisoliths”), Del Rio, Texas
Caliche glaebules, polished surface of a thin section,reflected light
“Syncline” and “anticline”, Buda/Del Rio contact,1.1 miles east of Comstock, US-90
Lock, B.E., (2000), GCAGS Trans.
Terra Rosa, Queretaro, Mexico
Carbonate Environments
• Subaerial exposure
• Freshwater – lakes and rivers
• freshwater algae (Chara, etc.) and cyanobacteria (stromatolites, oncoliths, etc.)
Algal-precipitated carbonate (LMC) on bottles etc., lake in New York state, USA
Dean, W.E. and T.D. Fouch (1983), AAPG Memoir 33, p. 115
Dean, W.E. and T.D. Fouch (1983), AAPG Memoir 33, p. 123
Oncoliths with gastropod nuclei.
Upper: - Recent, Michigan
Lower:- Flagstaff Formation(Paleocene), Utah
Oncoliths, Flagstaff Limestone (Paleocene-Eocene), Utah.Freshwater lake deposits.
Stromatolites, Green River Formation, Eocene, Utah, USA.
Dean, W.E. and T.D. Fouch (1983), AAPG Memoir 33, p. 119
SEM views ofChara, ostracods,
small clam, all from freshwater muds,
Lower Cretaceous,Arkansas, USA.
Travertine dams, pools, southern Tamaulipas State,
Mexico
Recent travertine, Seven Rivers, New Mexico
Shore of Great salt Lake, Utah.
inset: ooliths in thin section.
oolith sand
Carbonate Environments
• Subaerial exposure
• Freshwater
• Eolian– wind-blown carbonate sands (mainly coastal)
McKee, E. D., and W.C. Ward (1983), AAPG Memoir 33, p. 153
Carbonate eolianite, Castle Rock, Bermuda
Carbonate Environments
• Subaerial exposure
• Freshwater
• Eolian
• Coastal– transgressive/regressive?– arid/humid?– wave or tide dominated?– supratidal, intertidal, subtidal zones
CARBONATETIDAL FLAT MODELS
Andros Island, transgressive, humid,
mesotidal
marsh, tidal creeks,intertidal algal flats
beach ridge
Persian Gulf,regressive, arid,
microtidal
sabkha (supratidal),abundant evaporites,intertidal algal mat,
high and low energy lagoon,barrier island
Shinn, E.A. (1983), AAPG Memoir 33, p. 172
Supratidal
• Arid (sabkha)– deflation surfaces– intrastratal evaporites (mainly gypsum or
anhydrite) as lenticular crystals, nodules, contorted beds (enterolithic), massive layers (“cottage cheese”, mosaic or chicken-wire), halite molds
– dolomite
Enterolithic (contorted) anhydrite, deflation surface, Abu Dhabi sabkha
Shinn, E.A. (1983), AAPG Memoir 33, p. 196
cores of sabkha sediments, Abu Dhabi
marine subtidal sediment with gypsum crystals algal mat cottage cheese anhydrite nodules
Sabkha lithofacies, Arab Formation (Jurassic), Abu DhabiGrotsch, et al. (2003), GeoArabia v. 8, p. 47-86
Sabkha lithofacies, Arab Formation (Jurassic), Abu Dhabi
Grotsch, et al. (2003),GeoArabia v. 8, p. 47-86
Inner ramp cross-bedded ooliticgrainstones
Mid ramp and outerramp bioturbated
wackestones
gyps nodule molds
molds from dissolution of gypsum nodules, Cretaceous, Texas
Evaporites may dissolve and leave collapse breccias (Texas Cretaceous)
supratidal (sabkha)dolomite bed,
Cretaceous, Texas
parasequence boundary
dolomite (dark rock)
Supratidal
• Arid (sabkha)
• Humid– marshes (peat/coal), roots, cerithid
gastropods
Shinn, E.A. (1983), AAPG Memoir 33, p. 172
Andros Island
Intertidal
• Tidal creeks– high to moderate energy; alternating– grainstones, flat-pebble conglomerates– wavy, lenticular and flaser bedding,
bidirectional currents– fining-up
Shinn, E.A. (1983), AAPG Memoir 33, p. 192Tidal creek, based on Andros Island
Flat-pebble conglomerate, tidal flats. Kindblade Formation, Ordovician, Oklahoma.
Shoe, for scale
dolomitized tidal bedding, Cretaceous, Texas
“herring-bone” cross bedding (tidal, bi-directional), Cretaceous, Texas.
“herring-bone” cross bedding (tidal, bi-directional), Cretaceous, Texas.
Intertidal
• Tidal creeks
• Flats– fine grained sediments– scoured surfaces common– burrowed– algal laminations, stromatolites, birdseye
structures– surface crusts (dolomite)
Birdseye (= fenestral) structure, Mississippian, Kentucky, USA.
scoured surface
Algal mat, Baffin Bay, south Texas coast
“crinkly” algal mat lamination, Permian, New Mexico
Stromatolites, tidal flats. Kindblade Formation, Ordovician, Oklahoma.
5 cm
Arid tidal flats, Sonoran coast, Mexico (siliciclastic sands): note tidal creeks feedsediment on to the flats. Dark areas are halophyte plants.
Dolomitic crust (white) beneath erosional surface, Cretaceous tidal flats, El Abra.
Modern tidal flats, Sonora. Dolomitic crusts eroded by tidal creek.
Subtidal/Lagoon
• High or low energy, depending on lagoon size, etc.– carbonate mudstones to grainstones
• Salinity may fluctuate (fresh water flooding, high salinities from evaporation)– high stress: flora and fauna may not be normal marine
• miliolid forams etc., serpulids, ostracods, no echinoderms.
• Shoaling-up cycles
Peritidal cycles(supratidal/intertidal/subtidal),
Cretaceous, Texas
Peters et al., GeoArabia v. 8 (2), 2003
Peters et al., GeoArabia v. 8 (2), 2003
Surface-exposedsalt domes, Oman.
Blocks of interbedded
shallow waterlimestone are
scattered over the ground.
] saltlimestone reservoirs
Limestones were interbeddedwith the original salt (latestPrecambrian) and contain
stromatolites, crinkly laminationand other shallow water features. Microbial mat
limestones are dark and fetid,believed to be source rocks in deeper parts of the basin. Red
clastics are interbedded withthe carbonates.
Peters et al., GeoArabia v. 8 (2), 2003
Peters et al., GeoArabia v. 8 (2), 2003
Beach and/or Barrier Island
• High energy, coarsening-up sequence
• Seaward-dipping lamination, low-angle cross-bedding (summer-winter variation in beach foreshore slope), some higher angle landward-dipping cross-beds (offshore bars).
• Festoon cross-bedding in tidal channels (coarse-based units)
• Beach-rock (vadose and phreatic cement textures, marine cement mineralogies)
Inden, R.F., and C.H. Moore (1983), AAPG Memoir 33, p. 213
Festoon cross-bedding, tidal inlet channel
Beach rock, Bahia Adair, Sonora.
Thin-section photomicrograph, beach rock from Bahia Adair. Note aragonite needle cements