The Cretaceous-Paleogene boundary unit in the Gulf of Mexico; large-scale oceanic basin response to the Chicxulub impact

Author(s): Sanford, J. C.; Gulick, Sean P.; Snedden, J.
Author Affiliation(s): Primary:
University of Texas at Austin, Jackson School of Geosciences, Austin, TX, United States
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The prevailing theory for the Cretaceous-Paleogene (K-Pg) extinction event cites the Chicxulub asteroid impact on the Yucatan Peninsula as the catalyst for the global climatologic and ecologic crisis. This theory has been corroborated by a multitude of K-Pg boundary deposits observed globally in both boreholes and outcrops. The change in character of these deposits with proximity to the crater, from a millimeter-scale clay layer to a hectometer-scale carbonate sequence, supports a causal link between the boundary unit and the asteroid impact. Due to its passive marine setting and proximity to the Chicxulub crater, the Gulf of Mexico is the premier locale in which to study the near-field geologic effect of a massive bolide impact. Until recently, investigation of the K-Pg boundary deposit within the Gulf has been largely confined to outcrops and boreholes on the periphery of the basin due to the difficulty of observation of the boundary unit in the deep water. However, hydrocarbon exploration in the past decade has yielded significant borehole and seismic data that can be used to better understand the deep-water response to the impact and to gain a comprehensive regional understanding impact-related processes in the Gulf. Based on roughly 100 offshore and 300 onshore Cretaceous well penetrations, the K-Pg boundary is interpreted to range from a strictly erosional surface in shallow-water and coastal regimes to a mass transport deposit up to ∼400 meters thick. Depth-converted seismic data throughout the Gulf corroborate such thicknesses and reveal that the deposit is virtually ubiquitous throughout the deep water. For the first time, the K-Pg boundary deposit has been tied from the central Gulf to the Chicxulub crater, further establishing a causative link between the two. Biostratigraphic data in wells confirm the age of the deposit and document the presence of the "K-Pg boundary cocktail." Seismic data reveals areas of extensive debris flows and slump deposits on the lower slope of the Florida Platform, providing further evidence of massive sediment redistribution. Log character of the boundary deposit varies significantly, suggesting changes in both depositional style (e.g, mass flow deposit, collapsed platform block, etc.) and sediment source (e.g., Yucatan Platform, Florida Platform, Texas coast, etc.). Reinvestigation of the classic K-Pg boundary deposits in DSDP Leg 77 cores reveals evidence of several sequences of debris flows and/or turbidites with possibly unique sediment sources, furthering our understanding of small-scale sedimentary processes of impact-related deposition. Generally, evidence supports the theory that the Chicxulub impact was a source of extreme allogenic energy that drastically altered the Gulf Mexico at the start of the Cenozoic. Seismogenic ground roll and multiple episodes of tsunami, erosion, platform collapse, and remobilized sediment effectively overwhelmed and resurfaced the basin's existing depositional systems within a matter of weeks to months. Such processes resulted in the nearly ubiquitous and often extremely thick K-Pg boundary unit in the Gulf. These results yield insight into the near-field effects of a massive bolide impact in a passive marine setting and the ability of such an impact to instantaneously restructure an oceanic basin and its depositional systems.
Year of Publication: 2013
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Cores; Cretaceous; Deep Sea Drilling Project; Gulf of Mexico; IPOD; K-T boundary; Leg 77; Lower Paleocene; Marine sediments; Mesozoic; North Atlantic; Paleocene; Paleogene; Sediments; Stratigraphic boundary; Tertiary; Upper Cretaceous
Coordinates: N232000 N240000 W0842000 W0853000
Record ID: 2015070710
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