The Cretaceous-Paleogene boundary deposit in the Gulf of Mexico; oceanic basin response to the Chicxulub impact and geomechanics of reservoir-scale sand injectites, Panoche Hills, California

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Author(s): Sanford, Jason Charles
Source: 157p. Institution: University of Texas at Austin, Austin, TX, United States
Note: In English. 180 refs. Master's thesis
Summary: Given its passive marine setting and proximity to the impact basin, the Gulf is the premier locale in which to study the near-field geologic effect of a massive bolide impact. A thick (dm- to hm-scale) deposit of carbonate debris at the Cretaceous-Paleogene boundary is ubiquitous in the Gulf and identifiable on borehole and seismic data. Cores in the southeastern Gulf indicate that the deposit in the distal deepwater Gulf is predominately muddy debrite with minor turbidite. Mapping in the northern Gulf reveals that the impact redistributed ∼1.05×105 km3 of sediment therein, implying over 1.98×105 km3 Gulf-wide. Deposit distribution indicates that sediment derived from coastal and shallow-water environments throughout the Gulf via impact-initiated seismic and megatsunamic processes. The Texas shelf and northern Florida Platform margin were primary sources of sediment, while the central and southern Florida Platform sustained localized platform collapse. The ancestral Louann salt basin had significant variation in bathymetry that influenced post-impact deposition in the north-central and northwestern Gulf. Impact-mobilized sediment and processes were able to overwhelm virtually all topography and depositional systems at the start of the Cenozoic, blanketing the Gulf with carbonate debris within days. The Panoche Giant Injection Complex (PGIC) in central California is a complete injectite system. We measured hundreds of injectites over ∼600 m of stratigraphic thickness in two locales in order to determine geomechanical controls on injection. We document an injectite architecture in the PGIC that we interpret to reflect a reversal in paleostress state from reverse to strike-slip or normal with proximity to the paleoseafloor. We demonstrate that injectite aperture and bulk strain decrease with distance from the injection source. We model this behavior with three hydraulic fracture geometries and conclude that injectites formed via radially propagating hydraulic fractures. We document a northeast-southwest paleo-orientation preference of subvertical injectites, which reflects the control of Farallon plate subduction on stress state at the PGIC. We estimate that the PGIC was complete and active for ∼1 Ma and punctuated by ∼20-150 ky-long periods of quiescence based on thickness and spacing of extrudites in the PGIC.
Year of Publication: 2015
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Bolides; Boreholes; California; Cenozoic; Chicxulub Crater; Cretaceous; DSDP Site 536; DSDP Site 540; Deep Sea Drilling Project; Geophysical methods; Geophysical surveys; Gulf of Mexico; IPOD; K-T boundary; Leg 77; Lower Cretaceous; Lower Paleocene; Mass extinctions; Mesozoic; Meteors; North Atlantic; Paleocene; Paleogene; Paleogeography; Panoche Giant Injection Complex; Panoche Hills; Seismic methods; Stratigraphic boundary; Surveys; Tertiary; United States; Upper Cretaceous; Upper Paleogene
Coordinates: N232917 N232918 W0851234 W0851235
N234943 N234944 W0842214 W0842216
Record ID: 2016051530
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