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K-State Today

October 25, 2018

University of Texas at San Antonio's Alexis Godet to present geology seminar

Submitted by Angelina Butler

The College of Arts and Sciences' geology department will host Alexis Godet, assistant professor at the University of Texas at San Antonio, for a seminar at 4 p.m. Thursday, Oct. 25, in 213 Thompson Hall.

Godet will present "Forcing Mechanisms on Neritic Carbonate Sedimentation: Insights from the Early Cretaceous Urgonian Platform."

Abstract: Early Cretaceous greenhouse conditions favored the development of a wide intertropical climatic belt, where widespread shallow marine ecosystems efficiently produced platform carbonates. This research hypothesizes that climate triggered environmental and oceanographic changes that influenced carbonate factories of the Urgonian platform on the northern margin of the Tethys ocean. Three goals are achieved in a study area that extends from Switzerland to southeastern France: (1) development of a robust stratigraphic framework that permits platform-to-basin correlation, (2) identification of environmental changes using geochemical proxies, and (3) documentation of the impact of environmental stress in deposits of carbonate platforms.

First, the integration of available biostratigraphic, chemostratigraphic and sequence stratigraphic data constrains the duration of a prolonged period of condensation and/or non-deposition that starts in the late Hauterivian and is documented in the Helvetic Alps and the western Swiss Jura, respectively. Benthic carbonate production resumes in the end of the early Barremian, and photozoan assemblages of the Urgonian platform rise in the Late Barremian. Carbonate production is subsequently punctuated by a major period of slow down across the Barremian-Aptian boundary, and ceased in the early Aptian.

Second, the studied time period exhibits changes in nutrient levels as well as several environmental crises that resulted in the preservation of organic-rich deposits in (hemi-)pelagic settings. The Faraoni level (latest Hauterivian) results from the installation of more humid conditions and enhanced weathering on land that stimulated primary productivity, promoted the installation of mesotrophic conditions and participated to the development of bottom water anoxia, whereas oligotrophic conditions characterize the late Barremian.

Third, mesotrophic conditions that predate the unfolding of the Faraoni event coincides with heterozoan carbonate production, especially in the Helvetic Alps. This suggests that late Hauterivian climate change induced the adaptation of benthic communities to more stressful conditions under which suspension-feeding organisms produced larger volumes of carbonate sediments compared to heterozoan ecosystems. Stronger detritism during most of the early Barremian induced a major phase of drowning of heterozoan communities. Carbonate production resumed in two steps near the early to late Barremian boundary: heterozoan ecosystems colonized epicontinental sea as detrital input decreased, whereas the photozoan, Urgonian-type carbonate platform thrived under oligotrophic conditions later in the late Barremian.