T256 Oceans and Climates through Earth History: From Proxy Reconstructions to Model Assessments (Posters)

Wednesday, 7 November 2018
9:00 AM - 6:30 PM
Halls J-K

LOCAL BUT PRIMARY ORIGIN OF THE EARLY CAMBRIAN CARBON ISOTOPE RECORD FROM MOROCCO

Paper number: T256-2
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Carbon isotope excursions in Earth's history have been used to reconstruct changes in global carbon cycling and to correlate sedimentary strata intrabasinally and globally. However, the underlying assumption that these excursions represent global signals in the open ocean has not been adequately tested. Here, with multiple geochemical proxies (i.e., [Sr], δ44/40Ca and δ26Mg), we revisit the most expanded δ13C record of the early Cambrian from Morocco to investigate if this shallow-water carbonate record is representative of the open ocean, and what effect early marine diagenesis has had on the δ13C excursions used for stratigraphic correlation? Our [Sr] data show a linear correlation with δ13C, which is at odds with the large difference in their residence times if recording open-ocean signals — therefore either [Sr], δ13C, or both have been diagenetically altered. Two numerical diagenesis models applied to [Sr] and δ44/40Ca indicate that early marine diagenesis did not substantially alter the δ13C signals, but did change [Sr]. Coherent δ26Mg variations imply sediment-buffered dolomitization, consistent with the conclusion about the primary origin of the δ13C record. Therefore, while we do not have strong evidence that the δ13C signal reflects global seawater, we conclude that Morocco δ13C records at least a primary local signal that may be correlatable to other shallow water carbonate platforms globally.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-322134

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