Integrated Stratigraphy of Latest Cenomanian and Early Turonian Facies of Colombia
Tomas Villamil, Claudia Arango, 1998. "Integrated Stratigraphy of Latest Cenomanian and Early Turonian Facies of Colombia", Paleogeographic Evolution and Non-Glacial Eustasy, Northern South America
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Centime ter-scale stratigraphic anaJysis of facies deposited around the Cenomanian-Turonian (C-T) boundary in Colombia reveals that the interval is a condensed section caused by a series of transgressive pulses near the Cretaceous peak transgression with subsequent sediment trapping nearshore, omission and sediment starvation rn basinal facies. The condensed section thickens basinward and has a diachronous base and top: the base becomes younger landward whereas the top becomes younger basinward.
Facies across the C-T boundary in Colombia were interpreted as being deposited in a high-upwelling regime as evidenced by phosphate-rich shales, scattered chert beds with abundant nidiolarians, foraminifers filled with silica, changes in pianktic foraminifer populations, high values of total organic carbon (TOC up to 16%) and anoxic to dysoxic bottoms. Dysoxia was widespread, and affected the sediment-water interface and the water column.
For this paper, we used biostratigTaphic data to define and recognize the Cenomanian-Turonian bouadary in northern South America. Paleobiology, geochemistry, petrography, stratal geometries, and the modification of the paleogeography were used to characterize the uppermost Cenomanian-lowest Turonian stratigraphic interval (CTI) and to substantiate sea-level interpretations and other events occurring during this time. The CTT is here correlated to the proposed stratotype section in Pueblo, Colorado.
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Paleogeographic Evolution and Non-Glacial Eustasy, Northern South America
Paleogeographic Evolution and Non-Glacial Eustasy Northern South America - Published eustatic cycle charts commonly call for eustatic fluctuations of more the 40 m every few million years or less. These cycles are interpreted as eustatic, but, so far, waxing and waning of continental glaciations is the only known mechanism which clearly has the ability to drive such large, short-term eustatic fluctuations. High-magnitude, high-frequency ?glacio-eustatic cyclicity? may be a valid concept for times of continental glaciations, but what about times when such glaciations was absent from Earth? Why do cycle charts have a similar form and style for time periods with and without glaciation? Is it that we have missed the identification of a fundamental driving cause which is as important as glaciation and which might have operated during non-glacial times? Or, is it that we are confusing local and eustatic drivers of relative sea-level change? These persistent questions, and others, continue to cast doubt on the entire subject of sequence correlatability. The papers in this book collectively address these questions.
- chemically precipitated rocks
- lower Turonian
- sea-level changes
- sedimentary rocks
- South America
- upper Cenomanian
- Upper Cretaceous