T174 Precambrian Basin Analysis

Thursday, 29 October 2020
10:00 AM - 12:00 PM
Meeting Rooms

INTEGRATED LITHO-, CHEMO- AND SEQUENCE-STRATIGRAPHY OF THE EDIACARAN GAMETRAIL FORMATION ACROSS A SHELF-SLOPE TRANSECT IN THE WERNECKE MOUNTAINS, YUKON, CANADA

Paper number: T174-17
Program: Technical Sessions
Time: 11:20 AM – 11:25 AM

Authors

Abstract

The Ediacaran Shuram carbon isotope excursion (CIE) represents the largest negative δ13Ccarb excursion in Earth’s history. Despite ongoing debate about the origin and nature of this event, its isotopic expression has been widely used to correlate Ediacaran strata worldwide. Here, we examine Shuram-bearing Gametrail Formation across a shelf-slope transect in the Wernecke Mountains of Yukon, Canada, to elucidate the stratigraphic expression of this CIE. Thirteen detailed stratigraphic sections were measured of the Gametrail Formation across an ~100-km-long transect with m-scale sampling of carbonate for various isotopic analyses. Over 1000 δ13Ccarb measurements have been made with selected samples being analyzed for δ44/40Ca, δ26Mg, and major/trace element geochemistry. The Gametrail Formation increases in thickness by more than four-fold from the most proximal to the most distal locations along the shelf-slope transect. Multiple well-defined transgressive-regressive (T-R) sequences within the shelf system pass to cryptic conformable contacts within the slope. Along this depth transect, there is an ~10‰ δ13Ccarb shift in the nadir of the Shuram CIE, which is expressed within a diversity of sedimentary facies reflecting sedimentation along a distally steepened carbonate ramp. Inner ramp sections are characterized by dolostone facies with δ13Ccarb values reaching a nadir of -5.5‰, with more enriched δ44/40Ca and lower Sr/Ca. In contrast, slope sections are composed of limestone facies with δ13Ccarb data reaching a nadir of -15‰ and more depleted δ44Ca and higher Sr/Ca values. These data highlight a critical depth-dependent relationship in the nature and magnitude of the Shuram CIE.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-356393

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