Spectacular development of "Chalk" a soft lithology rock largely consisting of the remains of Coccolithophorids are fairly common in continents surrounding North Atlantic basin, but seem to be scarce or completely absent in marginal marine basins of Indo-Pacific region. Any suggestions please.
The chalk was deposited during the Upper Cretaceous period over about 35 million years. It is thickest inside the Central Graben (up to 2000 m). I have seen no convincing explanation for why the water was full of coccoliths during this period, as must have been the case. In my view, there is room for speculation that the water was especially suited for such calcified organic blooming. In 1990, I suggested that some similar carbonates may have been stimulated by seepage of mineral-rich porewater (see attachments). There could be some added CO2 and methane to the seawater from deeper-lying (Jurassic) source-rocks. We have to remember that the capping clays were not in place during this time, and we know that there was prolific hydrocarbon generation in the substratum sediments. Furthermore, we know that there are plenty of large faults where seepage can have been active all over the Central Graben flanks. There is also further discussion of this model in my book about 'Deep-water Coral reefs', see link below.
Book Deep-Water Coral Reefs. Unique Biodiversity Hot-Spots
Dear Syed Abbas
The previous work which deals with Smectite origin in Chalk of northern France as case study reflect the presence of this mineral in Chalk which is distributed insome parts of north Atlantic basin margin (Deconinck and Chamley, 1995). However the clay minerals are the one of components of Chalk.
link:http://www.minersoc.org/pages/Archive-CM/Volume_30/30-4-365.pdf
Zachos et al. (1989) may useful for your work
link:http://www.es.ucsc.edu/~jzachos/pubs/Zach_Arthur_Dean_89.pdf
I propose you check the work of Xiumian Hu, (2009)that show you stratigraphic relationship between red beds of north Atlantic basin with chalk as alternation sequence.
link: https://books.google.com/books?id=mNU370RDSrUC&pg=PA67&lpg=PA67&dq=factor+os+Chalk+late+cretaceous+deposition+of+north+atlantic&source=bl&ots=DUyvPkE_-R&sig=Zv_xTKbB_txYnj_NWPAN6VgpVk8&hl=en&sa=X&ved=0CDUQ6AEwA2oVChMI7syR1fGUxwIVARIUCh1kUgay#v=onepage&q=factor%20os%20Chalk%20late%20cretaceous%20deposition%20of%20north%20atlantic&f=false
Wagner et al. (2009) have mentioned to relationship between Upper Cretaceous nanofossil distribution and Chalk deposition.
link: http://onlinelibrary.wiley.com/doi/10.1029/2003PA000898/full
Regards
Massih
Dear colleague Martin
Thanks for providing important links and insight. Do you think your Central Graben model could also be valid for Chalk development in other areas like Western Interior and elsewhere in North Atlantic?
Yes, indeed, Sayed,
wherever there have been fluids coming up from the mantle, through the crust, like there are in all areas with rifting, subduction and volcanism, prior to sediment basin formation. And wherever there has been a high input of CO2 and/or CH4 and other hydrocarbons.
Dear Colleague KMT
Please elaborate on:.. "blooms" requires special nutrient conditions",...Are there other crucial factors besides nutrients which leads to calcareous, siliceous and organic walled Phytoplankton bloom in general and in rather closed North Atlantic basin during Late Cretaceous with subdued terrigenous input? Is it exclusive sequestration of atmospheric CO2 during Coccolith bloom? Thanks.
Several points should be stressed. Firstly, end of mid-Cretaceous Greenhouse regime resulted in a decrease of sea water temperatures. Than, saturation of sea water with calcium carbonate and its equilibrium with CO2 amount in atmosphere enabled easy forming of calcium carbonate tests. Renewing of sea current system was also essential (probably more than the nutrients input - calcareous nannoplankton is oligotrophic if compared with e.g. radiolarians). Paleogeographic location was important as stenohaline (both nanno. and micro-) plankton is limited by rainy areas.
Coccolith abundance is the highest close to subpolar waters not in the tropics... Plankton life in hot (almost sterile) waters ("mare azzurro") is not easy. However, the temperature is not the only proxy...Radiolarians are eutrophic microorganisms, only minor part of them can use (partial) autotrophy,,,
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