Cyclostratigraphy and sedimentation of the Cenomainan-Turonian Tuscaloosa Marine Shale.

摘要

A cyclostratigraphic and geochemical analysis was conducted on the basal high resistivity zone of the Tuscaloosa Marine Shale to determine if orbital forcing is apparent in mineralogical data suites. Geochemical data suites obtained via X-ray diffraction from five cored wells located near the southern Mississippi/Louisiana border were used in the study. The results were used in concert with previously published insolation and biostratigraphic data and unpublished stable carbon isotope data to determine sedimentation rate, to identify and correlate the Cretaceous Oceanic Anoxic Event 2 (OAE 2) recovery period within the studied interval, and to determine the possible mechanisms of orbital forcing. Results from multitaper spectral analysis and average spectral misfit reveal multiple statistically significant stratigraphic frequencies in four of the five studied wells, as well as significant correlation to orbital cyclicity (p 0.05). Sedimentation rates range from 8.811 cm/ky to 12.321 cm/ky and average 10.332 cm/ky. TOC and resistivity values were used to correlate the OAE 2 recovery interval between the studied wells. Calculated durations range from 212 ky in the most distal well location to 251 ky in more proximal locations. The published insolation and unpublished stable carbon isotope data were used to anchor the time scale based on the terminus of OAE 2 at approximately 94 Ma. Based on geochemical proxies, it is proposed that variations in insolation and the hydrologic cycle drove cyclic sedimentation by varying primary productivity and continental weathering.