Analysis of the influence of ocean water conditions on the composition of the organic component deposited with the mineral fraction of bottom sediments by means of palynology (offshore Uruguay).

Supervisor: Ian C. Harding (Univ. Southampton).
The quantification of organic matter in modern ocean sediments is a research topic highly relevant for the exploration of hydrocarbons in ancient sedimentary rock successions, so that it is possible to determine how organic carbon-rich oil and gas source rocks were originally deposited. This work seeks to understand of mechanisms leading to the deposition of organic carbon in the modern bottom sediments of the Atlantic margin South America. This study has investigated samples deposited at water depths between the 800 m and 3200 m from along the continental slope offshore of the Rio de la Plata province, Uruguay. The samples were originally collected from March to April of 2014 along the Geotraces cruise transect D357/GA10E (UKGeotraces 40°S) in the southern Atlantic Ocean by Stratasolve Ltd., with the purpose of extracting short piston core sediment samples for Shell International Exploration & Production B.V. Core top samples from two shelf-to-slope transects have been studied here for their organic content (percentage of total organic carbon -%TOC- and palynomacerals). Cluster analysis of the palynomaceral data in combination with existing oceanographic and sedimentological data has provided an understanding of the influence of the Oxygen Minimum Zone (OMZ) of Upper Circumpolar Deep Water (UCDW) on the preservation of organic matter (total organic carbon, phytoclasts and marine and terrestrial palynomorphs) in the bottom sediments. Three different onshore-offshore domains have been identified, characterised by different suites of organics, which suggest a link between the influence of water currents, the abundance of particulate organic matter and the depositional onshore-offshore trend.