T283 Marine Redox Evolution: Controls and Consequences II

Wednesday, 3 November 2010
1:30 PM - 5:30 PM
Room 203

HYPOXIA DEVELOPED AT THE PALEOCENE-EOCENE THERMAL MAXIMUM IN SVALBARD, NORWAY

Paper number: T283-10
Program: Technical Sessions
Time: 3:50 PM – 4:05 PM

Authors

Abstract

Four sections comprising latest Paleocene and Early Eocene strata have been studied in detail from the Central Basin of Svalbard (Arctic Norway) as a part of the pACE program (http://www.wun.ac.uk/external/pACE/). These sections cover the siliciclastic Frysjaodden Formation, and are located about 40 km apart. The formation is composed of offshore shelf, prodelta to basal delta front strata, representing a transgressive – regressive sequence deposited under partly brackish water conditions. The maximum flooding event is located at the Paleocene-Eocene Thermal Maximum (PETM) developed in the lowermost part of the Frysjaodden Formation.

Global climatic change across the Paleocene-Eocene transition, culminating in the PETM, resulted in increased chemical weathering triggered by warm and humid conditions. In the Svalbard sections, it is seen e.g. in the well developed clay mineralogical changes from smectite- to kaolinite-dominated phases. At the sea floor dark grey, organic rich, finely laminated, non-bioturbated clays were typically deposited. The shales are characterized by agglutinated foraminiferal assemblages of extremely reduced diversities showing a marked faunal turnover along with a clear-cut drop in the Th/U ratios of bulk geochemical analysis.

The climatic changes are typified by increased average temperatures and level of precipitation. These have resulted in well developed thermohaline stratification in the water masses of the rather shallow prodelta shelf sea, and the establishment of hypoxic bottom water conditions. Such relations are reflected in the organic rich, finely laminated and non-bioturbated, low Th/U black shales containing foraminiferal assemblages of environmentally restricted nature. These developments were further strengthened by the ongoing transgression and deepening of the depositional basin. A closely-related (Early Eocene) development in the Arctic Ocean is highly brackish surface waters and bottom water oxygen depletion.