1& 2 Drill hole137: Common association of fossils Globogerina, Globotruncana form., Globotruncana Maya. Epoch and radiometric age: Late Cretaceous ( 85- 75 My) Drill hole11: Common association of fossils Globogernia, Uvigerina, Globorotalia and Orbulina Epoch and radiometric age: Miocene (15- 23 My) Drill hole10: Common association of fossils Globotruncana Maya, Globigerina and Globotruncana form. Epoch and radiometric age: Late Cretaceous ( 85- 75 My)
Transcript
1& 2
Drill hole137:
Common association of fossils Globogerina, Globotruncana form.,
Globotruncana Maya.
Epoch and radiometric age: Late Cretaceous ( 85-75 My)
Drill hole11:
Common association of fossils Globogernia, Uvigerina, Globorotalia and
Orbulina
Epoch and radiometric age: Miocene (15- 23 My)
Drill hole10:
Common association of fossils Globotruncana Maya, Globigerina and
Globotruncana form.
Epoch and radiometric age: Late Cretaceous ( 85-75 My)
Drill hole105:
Fossil association is Brotzenia, Lenticulinia, Bairdia and Saccocoma
Epoch and radiometric age: Late Jurassic (152-158 My)
3. Age of basalt floor at drill hole locations:
Drill Hole 137: 95-100 My
Drill Hole 11: 10 My
Drill Hole 10: 80 My
Drill Hole 105: 150 My
4.
Drill No Basalt (in My) Fossil (in My)
137 95-100 85-75
11 10 15-23
10 80 85-75
105 150 152-158
At present for older oceanic floor fossil dates are more reliable
5.
6. Drill hole 11 is at 2 cm from rift axis = 20*20 = 400 km =400*100000
cm is distance
Hence separation rate = 400*100000 cm/(10*10^6) yr = 4 cm/yr
10 My 80 My
150 My
100 My
7. Distance between both boreholes = 10 cm = 100 mm
Is equivalent to = 100 *20*100000 cm = 200* 10^6 cm
Time difference = 70 My
Hence rate = 200/70 = 2.8 cm/yr
8. distance is 24 cm
Now for 10 cm it took 70 My on average rate between 10 and 105
boreholes,
Hence for 24 cm it will take,
70*24/10 = 168 My
Hence the age when rifting began was 168 My before present
9. The reason for finding only oozes are they are representative sediments
deposited far from the sea in relatively calm seas where sediments influx
from the land is not available. Deeper parts of oceans are calm places for
forming oozes. Most of the sand is deposited along continental slope or
above and since because of subduction these zones are constantly
subducted and only deeper sediments appear to remain on oceanic crust.
10. According to theory of plate tectonics as we move away from rift
zones (mid-oceanic ridges) we find older sediments and also as we go
down we also find older sediments/ rocks. If we start finding deposits of
Paleozoic beneath currently found Mesozoic deposits it is only to be
expected since age is growing as we move down. Hence finding
Paleozoic deposits will not disprove continental drift.
