The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development

Christopher M. Lowery, Robert Cunningham, Craig D. Barrie, Timothy Bralower, John W. Snedden

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Despite their name, Oceanic Anoxic Events (OAEs) are not periods of uniform anoxia and black shale deposition in ancient oceans. Shelf environments account for the majority of productivity and organic carbon burial in the modern ocean, and this was likely true in the Cretaceous as well. However, it is unlikely that the mechanisms for such an increase were uniform across all shelf environments. Some, like the northwest margin of Africa, were characterized by strong upwelling, but what might drive enhanced productivity on shelves not geographically suited for upwelling? To address this, we use micropaleontology, carbon isotopes, and sedimentology to present the first record of Oceanic Anoxic Event 2 (OAE2) from the northern Gulf of Mexico shelf. Here OAE2 occurred during the deposition of the well-oxygenated, inner neritic/lower estuarine Lower Tuscaloosa Sandstone. The overlying organic-rich oxygen-poor Marine Tuscaloosa Shale is entirely Turonian in age. We trace organic matter enrichment from the Spinks Core into the deepwater Gulf of Mexico, where wireline log calculations and public geochemical data indicate organic enrichment and anoxia throughout the Cenomanian-Turonian boundary interval. Redox change and organic matter preservation across the Gulf of Mexico shelf were driven by sea level rise prior to the early Turonian highstand, which caused the advection of nutrient-rich, oxygen-poor waters onto the shelf. This results in organic matter mass accumulation rates 1–2 orders of magnitude lower than upwelling sites like the NW African margin, but it likely occurred over a much larger geographic area, suggesting that sea level rise was an important component of the overall increase in carbon burial during OAE2.

Original languageEnglish (US)
Pages (from-to)1316-1335
Number of pages20
JournalPaleoceanography
Volume32
Issue number12
DOIs
StatePublished - Dec 2017

Fingerprint

black shale
upwelling
water depth
anoxia
Turonian
organic matter
micropaleontology
Cenomanian-Turonian boundary
productivity
oxygen
ocean
highstand
sedimentology
accumulation rate
carbon isotope
shale
advection
organic carbon
sandstone
Cretaceous

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Palaeontology

Cite this

Lowery, Christopher M. ; Cunningham, Robert ; Barrie, Craig D. ; Bralower, Timothy ; Snedden, John W. / The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development. In: Paleoceanography. 2017 ; Vol. 32, No. 12. pp. 1316-1335.
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The Northern Gulf of Mexico During OAE2 and the Relationship Between Water Depth and Black Shale Development. / Lowery, Christopher M.; Cunningham, Robert; Barrie, Craig D.; Bralower, Timothy; Snedden, John W.

In: Paleoceanography, Vol. 32, No. 12, 12.2017, p. 1316-1335.

Research output: Contribution to journalArticle

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