Late Pleistocene to Holocene sedimentology, palaeoceanography and micropalaeontology of the Uruguayan continental slope

McGuire, Cian James

Abstract

This study utilises an extensive set of sediment cores collected from a largely unstudied contourite and turbidite depositional system located on the Uruguay continental margin to identify a method of distinguishing deposits in the deep sea that are sourced from either gravity or bottom current sedimentary processes. The cores acquired by BG Group in 2014 targeted areas of the ocean floor that encompass both Late Pleistocene to Holocene age) large sediment drifts and large downslope canyons, where turbidite and contourite deposition occurs simultaneously. Core, sediment and micropalaeontological analysis has been used to answer three basic questions 1) Do the sediments collected from different geomorphic settings owe their origin to along-slope (contourite) or gravitational (turbidite) transport? 2) Do the drift sediments contain a record of palaeoceanographic change? and 3) Can micropalaeontologcial analysis resolve long-standing problems with differentiating along- and down-slope processes in the geological record.
The presented study provides new data resolving these three questions for the upper, middle and lower Uruguayan slope. The new data comprises;
1. A detailed examination of the sedimentary facies of the (LatePleistocene to Holocene) Uruguay slope, while ground-truthing interpretations from seismic and bathymetric data collected from the same area that is broadly contemporaneous
2. A reconstruction of watermass migration using stable isotope, elemental ratios and foraminiferal indices accumulated on the Uruguay slope since the Last Glacial Maximum
3. A classification of foraminiferal assemblages for that are likely to be indicative of specific sedimentary facies in turbidite and contourite deposits in order to distinguish these facies from one another in a sedimentary environment where both contourite and turbidite deposition has occurred.
This data elucidates some important new insights into the studied system and more broadly contourite and turbidite deposits globally:
1. A new model of mixed sedimentary system evolution on the Uruguay slope since the Last Glacial Maximum and how it is intrinsically linked to bottom-current/seafloor interactions
2. A new model for the flux of Antarctic sourced watermasses into the Atlantic basin across deglaciation
3. A new criterion for distinguishing contourites and from turbidite facies by using benthic foraminiferal ecological disturbance-succession patterns.

Citation

McGuire, C. J. Late Pleistocene to Holocene sedimentology, palaeoceanography and micropalaeontology of the Uruguayan continental slope. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4223202

• Thesis Type: Thesis
• Deposit Date: Jul 5, 2021
• Publicly Available Date: Feb 23, 2023
• Keywords: Geology; Geography
• Public URL: https://hull-repository.worktribe.com/output/4223202
• Additional Information: Department of Geography, Geology and Environment, The University of Hull
• Award Date: Dec 1, 2019