Horst, Peter A. and Maurrasse, Florentin J. M. R. (2005): Geochemistry of Cenomanian deposits from the western Tethys at DSDP Site 386 and 144; paleoceanographic and tectonic implications

Leg/Site/Hole:
DSDP 14
DSDP 43
DSDP 14 144
DSDP 43 386
Identifier:
2007-030077
georefid

Creator:
Horst, Peter A.
Florida International University, Department of Earth Sciences, Miami, FL, United States
author

Maurrasse, Florentin J. M. R.
author

Identification:
Geochemistry of Cenomanian deposits from the western Tethys at DSDP Site 386 and 144; paleoceanographic and tectonic implications
2005
In: Anonymous, Geological Society of America, 2005 annual meeting
Geological Society of America (GSA), Boulder, CO, United States
37
7
458
High-resolution stratigraphic analyses, including Total Organic (TOC) and Total Inorganic Carbon (TIC), organic-carbon-isotopes (delta (super 13) C (sub org) ), and minor elements, were carried out on Cenomanian sediments from DSDP Site 386 (Bermuda Rise; 4,782 meters) and Site 144 (Demerara Rise; 2,957 meters). The results reveal a relationship related to existing paleoclimates, modulated by paleophysiography, that controlled paleodepths and paleoenvironmental conditions. Sediments at Site 386 show high-frequency varicolored layers alternating from light tan to various shades of red, green, gray, and black. TIC ranges from 0% to 67%, and averages 2%. TOC ranges from 0% to at least 16.6%, and averages 1.4%. Clay content, expressed as relative Si wt%, ranges from 4.5% to 44%, with an average of 29%. delta (super 13) C (sub org) values range between -27ppm and -23ppm, and the interval studied shows no apparent expression of the well-documented carbon-isotope "spike" of the Cenomanian-Turonian boundary. The mid-Cenomanian double peak, however, seems to be present. Sediments at Site 144 are olive gray to black throughout, with TIC consistently higher than at Site 386, ranging from 15% to 84%, with an average of 44%. Similarly, TOC ranges higher, from 3% to 14%, and averages 9.6%. Clay content ranges from 3% to 12.5%, and averages 6%. delta (super 13) C (sub org) values range between -28ppm and -27ppm, although carbon-isotopes display neither the Cenomanian-Turonian boundary "spike" nor the mid-Cenomanian double peak. Patterns of variations of the different parameters imply that recurrent paleoceanographic conditions suggestive of climatically-induced fluctuations favored frequent preservation of TIC and TOC at Site 144, but only occasionally at Site 386. Differences in facies between the two sites must reflect their respective paleobathymetry, and variations in TIC/TOC recorded at Site 386 are interpreted to represent fluctuations that affected local paleoproductivity as well as the CCD level. We surmise that elemental results indicative of high clay contents at Site 386 can be attributed to volcanic influences, but not at Site 144. Average delta (super 13) C (sub org) values for both sites tend to be isotopically lighter than those of Recent samples, and thus are compatible with earlier works that concluded CO (sub 2) concentrations were higher during this time period due to tectonovolcanic events.
English
Coverage:Geographic coordinates:
North:31.1113
West:-64.1457East: -54.2031
South:9.2714

Stratigraphy; Isotope geochemistry; Atlantic Ocean; Bermuda Rise; C-13/C-12; carbon; Cenomanian; color; Cretaceous; Deep Sea Drilling Project; Demerara Rise; DSDP Site 144; DSDP Site 386; Equatorial Atlantic; fluctuations; geochemistry; isotope ratios; isotopes; Leg 14; Leg 43; lithofacies; lower Turonian; Mesozoic; North Atlantic; Northwest Atlantic; organic carbon; organic compounds; paleo-oceanography; paleobathymetry; paleoclimatology; paleoenvironment; patterns; productivity; sediments; stable isotopes; stratigraphic boundary; tectonics; Tethys; total organic carbon; Turonian; upper Cenomanian; Upper Cretaceous; variations;

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