Admissions > PhD by research > Research Projects > Organic matter alteration processes through time in recent evaporitic sediments - insights from the Abu Dhabi sabkha

Organic matter alteration processes through time in

recent evaporitic sediments - insights from the Abu

Dhabi sabkha

Supervisors: Professor Richard Pancost 1, Dr Fiona Whitaker 2,
Dr Miroslaw Slowakiewicz 1 and Professor Maurice Tucker 2

1 School of Chemistry, 2 School of Earth Sciences

Context: This project considers the transformation of organic matter during early diagenesis in carbonate-evaporite systems to give a better understanding of the formation of source rocks for hydrocarbons. Evaporitic environments are amongst the most productive sedimentary settings for organic matter, evidenced by the prolific hydrocarbon production from many evaporitic formations. This arises not only from special reservoir properties of the platform settings but also from early diagenetic transformations of organic matter and mineral diagenesis.

Sabkhas are enriched in various microbialite and microbially-influenced lithofacies. Despite an extensive body of work, little is known about the diversity, abundance, and physiology of mat-associated archaea, in particular methanogens, and the corresponding biosignatures imparted by these organisms on the rock record. Even less is known about the generation of hydrocarbons during the early stages of diagenesis associated with the transformation from the living system to the ancient rock. Biologically-produced organic compounds are subjected to diagenetic changes such as defunctionalization, isomerization, aromatization, as well as microbial degradation of the organic matter. Modern and recent environments, such as the Abu Dhabi sabkha, offer a window into understanding these early alteration processes.

Objectives: This project will address a number of significant research questions:

  1. How is organic matter in evaporitic settings progressively lost or altered over time and what are the rates of change? What mechanisms control organic matter preservation and alteration in carbonate-evaporite environments?
  2. How are these processes influenced by the variety of modern sabkha/hypersaline mats and other materials?
  3. Can these processes be replicated in laboratory experiments in order to explore controls on artificial maturation of sediments?
  4. Can key elements of these systems be replicated in reactive transport models? How can this approach be used to predict the distribution of organic matter preservation and associated diagenesis?

Approach: This project will use geochemical techniques in order to estimate the origin of organic matter from the various sources, many of which are associated with the predominant mat-building organisms in the shallow water restricted environments. Sediments and pore fluids will be characterized in a sequence of recent to sub-recent material of mats of increasing age from an Abu Dhabi sabkha. Biochemical processes will be tracked through examining biomarker compounds. Laboratory experiments will enable identification of key controls on organic-matter maturation under a range of conditions. Numerical models of fluid flow and reactions will be constructed to represent these systems and their utility for prediction of organic matter preservation and associated diagenesis explored. Results will be compared with remnant organic matter in much older organic–rich deposits, such as the Upper Permian Zechstein carbonates of western Europe.

The proposed research will improve our understanding of organic matter alteration and preservation in sediments, as well as the processes operating in the early stages of diagenesis. This will help considerably in the prediction of hydrocarbon occurrence in frontier, as well as mature basins.

The student will receive training in characterisation of pore water and sediment from modern to recent environments and collection and analysis of organic biomarker compounds in young and ancient carbonates and evaporites. Field and laboratory techniques will be supplemented with numerical simulations using the reactive transport code TOUGHREACT. The project benefits from a cross-disciplinary research culture, providing a sound foundation for a career in academia or the hydrocarbon industry.

Organic mats from sabkhas of Abu Dhabi (photos courtesy of Maurice Tucker)



For further information please contact Fiona.Whitaker@bristol.ac.uk or R.D.Pancost@bristol.ac.uk

Last updated: 26/1/12