Carbonate Microbialite

Geobiology explores the interactions between the physical earth (rocks, minerals, sediments, soils) and the biosphere (particularly microbes). Our geobiological research spans huge temporal and spatial timescales – from ancient microbially-mediated sedimentary rocks to modern biogeochemical cycling of carbon, nutrients and trace elements in sediments and soils.

We seek to understand how microbial processes govern biogeochemical cycles, how the activities of microbes are recorded in the rock record, and how the biosphere and the geosphere have co-evolved. This work brings together researchers from the Geosystems and Physical Geography research groups. Within the Geosystems group, we also have strong links with the Palaeoclimate research theme. 

Academic staff

Rebecca Bartlett (Geosystems and Physical Geography)

Rebecca is a biogeochemist, specialising in nutrient cycling and environmental change in modern and past environments. Her research focuses on the biogeochemistry of peats, soils and sediments during environmental disturbance; the subsurface microbial response to natural and anthropogenic changes in atmospheric sulphur deposition, temperature, storms and floods, mineral reactivity and chemical pollution. Using a combined field and laboratory approach, Rebecca’s work examines the small-scale (local) consequences of long-term (global) changes to the environment, and subsequent impacts on pH, carbon dynamics, major nutrient cycles and water quality. 

James Bendle (Geosystems)

James’ training is in biogeochemistry, palaeoceanography and palaeoclimatology, especially the study of the source, structure, and distribution of naturally occurring compounds (biomarkers) such that their presence in ancient or modern ecosystems can be used to elucidate processes or environmental conditions. He specializes in the development and application of biomarker proxies in marine & terrestrial environments and applications ranging from long term Cenozoic to high-resolution Holocene climate evolution. He has worked with a range of paleoclimate archives including marine and lake sediments, ice-cores and speleothems. 

Sarah Greene (Geosystems)

Sarah is a palaeoclimatologist, geobiologist, and numerical modeller studying the biogeochemical cycling of carbon between the atmosphere, the ocean, and marine sediments. Particular research interests include mass extinctions and other rapid carbon cycle perturbations, multi-mullion year carbon cycle trends (co-evolution of life and the carbon cycle), and how biogeochemical cycling within marine sediments influences the rock record. Sarah also studies microbially-mediated carbonate rocks, such as stromatolites, to gain insight into past climates and environments. 

Sami Ullah (Physical Geography)

Sami is interested in the biogeochemical transformations of nitrogen (N) and its linkages to carbon cycling in complex landscapes including forest, peatland/wetland, grassland and cultivated soils. The impetus is to advance mechanistic understanding of the response of key biogeochemical functions in soils (e.g. denitrification, N & C mineralization, biological nitrogen fixation, greenhouse gas fluxes and soil enzyme activity) to land-use and global change at catchment scale. 

Sami’s research is underpinned by the development and application of novel analytical field techniques including stable isotopes and high-resolution sensor technologies to explore novel relationships between nutrient cycling, plant-microbe interaction and environmental conditions. 

This knowledge supports the development of new conceptual frameworks and feeds into dynamic ecosystems models for a more realistic assessment of the threshold of biogeochemical functional breakdowns under perturbations. This is critical for identifying actions for functional resilience of soils and agricultural sustainability 

James Wheeley (Geosystems)

James is a carbonate sedimentary geologist with a particular interest in Palaeozoic carbonate sedimentary systems, especially those of the Ordovician. James also researches conodont oxygen isotopes to elucidate conodont palaeoecology and seawater temperature changes. Recent work has been on Ordovician material from Anticosti and Newfoundland, Canada. Limestone samples collected from Anticosti have also been analysed for uranium isotopes; these tell us about global ocean redox conditions during the end Ordovician mass extinction.


The group has a suite of research-quality microscopes and imaging facilities including three transmitted light Zeiss AxioScopes, Zeiss and Leica stereoscopes, as well as a Phenom ProX desktop SEM and Philips XL30, both with EDS capability.

Our sediment experiment laboratories include anaerobic chambers and growth incubators for environmental simulations, and extraction apparatus for mineral speciation.

Within the School we have access to stable isotope (IRMS), trace metal (ICP-OES, ICP-MS), Greenhouse Gas chromatograph, TOC-TN, Ion Chromatograph (Dionex) and Skalar Flow Injection Colorimetric analysers for the analysis of fossil carbonates, soil chemistry and greenhouse gas fluxes, respectively.

GC-MS and GC-IRMS facilities are available for fossil biomarker, 13C  and 15N tracing of carbon and nitrogen cycling in soil and water.