Preprints
https://doi.org/10.5194/cp-2021-25
https://doi.org/10.5194/cp-2021-25

  15 Mar 2021

15 Mar 2021

Review status: this preprint is currently under review for the journal CP.

Enhanced Terrestrial Runoff during Oceanic Anoxic Event 2 on the North Carolina Coastal Plain, USA

Christopher M. Lowery1, Jean M. Self-Trail2, and Craig D. Barrie3 Christopher M. Lowery et al.
  • 1University of Texas Institute for Geophysics, Austin, TX, USA
  • 2United States Geological Survey, Reston, VA, USA
  • 3GeoMark, LTD, Houston, TX, USA

Abstract. A global increase in the strength of the hydrologic cycle drove an increase in flux of terrigenous sediments into the ocean during the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2) and was an important mechanism driving nutrient enrichment and thus organic carbon burial. This global change is primarily known from isotopic records, but global average data don't tell us anything about changes at any particular location; such reconstructions of local terrigenous flux can help us understand the role of regional shifts in precipitation in driving these global trends. The North Atlantic basin was one of the epicenters of enhanced organic carbon burial during OAE2, and so constraining terrigenous flux is particularly important in this region; however, few local records exist. Here, we present two new OAE2 records from the Atlantic Coastal Plain of North Carolina, USA, recognized with calcareous nannoplankton biostratigraphy and organic carbon isotopes. We use carbon/nitrogen ratios to constrain the relative contribution of marine and terrestrial organic matter; in both cores we find elevated contribution from vascular plants beginning just before OAE2 and continuing through the event, indicating a locally strengthened hydrologic cycle. Terrigenous flux decreased during the brief change in carbon isotope values known as the Plenus carbon isotope excursion, and then increase and remain elevated through the latter part of OAE2. Total organic carbon values reveal relatively low organic carbon burial in the inner shelf, in contrast to black shales known from the open ocean. Organic carbon content on the shelf appears to increase in the offshore direction, highlighting the need for cores from the middle and outer shelf.

Christopher M. Lowery et al.

Status: open (until 10 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on cp-2021-25', Anonymous Referee #1, 25 Mar 2021 reply
  • RC2: 'Comment on cp-2021-25', Anonymous Referee #2, 19 Apr 2021 reply
  • EC1: 'Reply to reviews', Appy Sluijs, 19 Apr 2021 reply

Christopher M. Lowery et al.

Model code and software

USGS Data Release Jean Self-Trail, Christopher Lowery, and Craig Barrie https://doi.org/10.5066/P9V0U1NF

Christopher M. Lowery et al.

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