Paleocene depositional history of the Cretaceous-Paleogene impact basin, Yucatan Peninsula, Mexico
AuthorO'Malley, Katherine E.
KeywordSedimentation and deposition
MetadataShow full item record
AbstractIn the spring of 2016, the International Ocean Discovery Program set out on Expedition 364 to recover core from the peak ring of Chicxulub Impact Crater at Site M0077. In total, 829 m of core was collected spanning granite to Paleogene sedimentary rocks. From this core, we have a well-preserved record of the Paleocene, which represents ~10 million years post impact in just under 10 m of sedimentary rock record. This has presented an incredible research opportunity, as we have gained invaluable information on how the environment responded and recovered from the global catastrophe that was the Chicxulub Impact. The Paleocene at M0077 is highly condensed and comprised of predominantly pelagic carbonate rocks. High resolution core logging and thin section analysis were used to identify facies in the Paleocene. Facies include marlstone, argillaceous wackestone, foraminiferal wackestone, and rare coarser grained lithologies such as packstone and grainstone. Overall, the Paleocene exhibits a succession of rhythmically bedded cycles composed of marlstones grading to argillaceous wackestones and capped by foraminiferal wackestones. Coarser grained lithologies only exist in the lower and uppermost portion of the core. In total, 72 cycles that ranged from 5-30 cm thick are identified and grouped into six larger packages based on pattern similarities in color, lithology, ichnofabric indices, and geochemical data. These cycles are interpreted as parasequences, and show predictable stacking patterns that allow us to make sequence stratigraphic analyses. Each package represents one to two systems tracts, and some can be correlated to eustatic sea level change. Recorded in this core is the progression of an initial sea level lowstand immediately post impact, and the fluctuation between highstands, lowstands, and transgressive systems tracts that follow. Major and trace elements were analyzed throughout the core, as well as delta¹³Corg and delta¹⁵Nbulk values. Three sets of geochemical proxies (paleoredox, detrital input, productivity) were used to provide insight into paleoecological conditions. Initial conditions in the crater show a period of high productivity, which tapers off within a million years post impact. Redox conditions vary, and show one major anoxic event, with other enrichments likely representing periods of pore water euxinia or increases in stratification leading to a more robust redox gradient.
DescriptionThesis (M.S.) University of Alaska Fairbanks, 2020
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High-Resolution Paleoceanography Of The Gulf Of Alaska, Subarctic Northeast Pacific Ocean, Since The Last Glacial Maximum: Insights Into A Dynamic Atmosphere-Ocean-Ecosystem Linkage At Decadal To Millennial TimescalesAddison, Jason A.; Beget, James E.; Finney, Bruce P.; Bigelow, Nancy H.; Naidu, A. Sathy; Stockwell, Dean A.; Wooller, Matthew J. (2009)Environmental conditions in the Subarctic Northeast Pacific Ocean are an important component of North American climate patterns, as well as a potential driver of Northern Hemisphere climate variability. The North Pacific Ocean is also the terminus of modern global thermohaline circulation, suggesting that paleoceanographic records from this region have the potential to preserve evidence of both climate forcing and response on regional and global scales. A suite of high-resolution marine sediment cores collected from the Gulf of Alaska margin in 2004 provide new paleoceanographic records at decadal and centennial timescales from fjord and continental slope environments. Key findings include: (i) decadal oscillations in marine productivity correlate with previously identified terrestrial records, indicative of forcing by the Aleutian Low pressure cell; (ii) the standard binary model of the modern Pacific Decadal Oscillation (PDO) as the major pattern of ocean-atmosphere variability is insufficient to describe the full range of Holocene paleoenvironmental fluctuations observed in Gulf of Alaska records of marine productivity, freshwater discharge, and bottom-water anoxia; (iii) the North Pacific ecosystem is a sensitive recorder of abrupt climate events observed in global records; and (iv) the fjords of Southeast Alaska contain a detailed record of volcanic activity and fallout events useful for developing composite chronological models of sedimentation that correlate with other regionally important stratigraphic records. Collectively, the results presented here will potentially redefine current theoretical models of atmosphere-ocean-ecosystem variability in the North Pacific Ocean, as well as contribute to a growing body of high-resolution paleoenvironmental time-series datasets from the high latitudes.
History of the Chukchi borderland and the Amerasia basin, Arctic OceanIlhan, Ibrahim; Coakley, Bernard J.; Johnson, Christopher A.; Houseknecht, David W.; Whalen, Michael T. (2018-08)Structural and stratigraphic interpretation of 2D multi-channel seismic (MCS) reflection profiles through recognition of the sub-surface reflection patterns and integration of the seismic interpretation with the other geophysical and geological data reveal the history of the Chukchi Borderland. This investigation provides new constraints for the tectonic development of the Amerasia Basin. North-striking normal faults of the Chukchi Borderland dissect the continental basement into the Chukchi Plateau, Northwind Basin and Northwind Ridge from west to east. A well-developed angular unconformity (Au) separates the stratigraphic section into sub and super-Au seismic units. Sub-Au units include: (1) seaward dipping reflections (SDRs) observed in the juncture between the North Chukchi-Toll Basins and Chukchi Plateau; (2) growth and folded strata in the Northwind Basin; (3) thrust faults in the Northwind Basin and over the Northwind Ridge; and (4) a clinoform sequence that downlaps onto the extended continental crust of the Canada Basin, supported by presence of SDRs and diapiric reflections within the crust. Au is inferred to correlate to the Hauterivian (LCu) and the Middle Jurassic (Ju) unconformities of the Alaska North Slope. The SDRs indicate that the southwestern margin of the Chukchi Borderland may be a rifted continental margin. Loosely constrained age control of a super-Au unit (inferred condensed section, perhaps correlative to Hauterivian pebble shale or the Jurassic upper Kingak shale units of Alaska North Slope) implies that the rifted margin subsided no later than the earliest Cretaceous, providing a plausible time constraint for Middle Jurassic-earliest Cretaceous rifting in the North Chukchi Basin. The growth strata and north-striking normal faults of the Northwind Basin are continuous with the extensional structures of the Mississippian Hanna Trough, providing a geologic linkage between the two. The folding and thrust faults reveal a phase of contraction confined to sub-Au units of the south and eastern Northwind Basin and Northwind Ridge. The clinoform sequence of the Northwind Ridge-Canada Basin is inferred to correlate with the Upper Jurassic-Lower Cretaceous Kingak shale unit of Alaska North Slope, implying that the extension of the crust beneath the western Canada Basin occurred no later than the Middle Jurassic. Super-Au strata (~16 km) onlap the condensed section, SDRs, growth and passive margin strata from west to east, tapering down to a few kilometers north and eastward across the seismic grid. These are part of the Aptian through Cenozoic Brookian megasequence, a series of clinothems, deposited across the foreland of the Chukotka and Brooks Range orogens. These strata were deposited by northward-migrating depositional systems that progressively filled the North Chukchi Basin and buried the southern flank of the Chukchi Borderland, and deposited along the Northwind margin of the Canada Basin. Another unit of growth strata is observed in the Northwind Basin, indicating another phase of extension of the Boderland. The Upper Cretaceous section of the Brookian megasequence is displaced by normal faults over the Chukchi Plateau and inferred age-equivalent strata over the Northwind Ridge. These constrain the second phase of extension of the interior Borderland to the Late Cretaceous to Paleocene. The recognition of the sub-Au units and continuity of the super-Au units across the area, north-striking normal faults, and the absence of east-directed thrust faults between the Northwind Ridge and Canada Basin invalidate one model proposed for tectonic development of the Amerasia Basin. Models that require significant relative motion between the Chukchi Shelf and Borderland since the Middle Jurassic are precluded by these observations.
Development And Application Of A Methodology To Estimate Regional Natural Conditions For Trace Metals In Marine Sediments Of Southcentral Alaska's Coastal RegionDasher, Douglas H.; Kelley, John J.; Duffy, Lawrence; Mueter, Franz; Naidu, A. S.; Perkins, Robert (2010)Increasing levels of resource development and population growth along Alaska's relatively pristine coastline require responsible environmental stewardship that is based on scientifically defensible monitoring and assessment. This thesis develops a methodology to assess the spatial distribution of coastal sediment trace metals and estimate their natural condition along Alaska's coastline. Marine sediments provide a better integrated long-term signal for naturally occurring and anthropogenic chemicals than repeated water measurements. The first of three manuscripts reports on marine sediment trace metal concentrations from a probabilistic sampling survey of Alaska's Southcentral coastal region. Results are described on a proportional basis, i.e., percent of estuary area, for the distribution of As, Cd, Cr, Cu, Pb, Hg, Ni, Ag, and Zn in the sediments. With the exception of naturally elevated Cr and Ni at a site bounded by a chromite ore body, sediment trace metal concentrations measured represent non-analmous levels. The second manuscript develops natural conditions for fluvial trace metal inputs from two major Southeast Alaska coastal watersheds: Cook Inlet and Copper River. The stream sediment trace metal natural conditions place levels in the adjacent coastal sediments into context. Two exploratory data analysis techniques, the Tukey Box plot and Median + 2 Median Absolute Deviation, combined with geochemical mapping are used to develop stream sediment trace metal natural conditions. The third manuscript builds on the first two to develop a methodology to estimate coastal sediment natural conditions. Population estimates for the cumulative area 90% UCB 95% sediment trace metal of interest obtained from the sampling survey methodology and screened reference sites is used to establishing an upper threshold value for regional natural conditions. While this work establishes natural condition marine sediment trace metal levels for this region, the significance of these levels from an ecotoxciological perspective remains to be established. Additional studies are needed along other sections of Alaska's coastline, coupled with biological assessments, if Alaska is to develop relevant sediment quality guidelines.