Prof Cathy Hollis

Limestones: an essential user guide to sediments that dissolve, precipitate and grow

Carbonate sedimentary rocks form through the accumulation of organisms and chemically precipitated calcium carbonate, usually on the sea floor. They preserve fragments of marine organisms, which are sensitive to temperature, salinity and seawater chemistry during their growth, and they therefore provide an exceptional record of evolutionary and climatic change through Earth history.  Carbonate sediments are also highly reactive, dissolving and precipitating in surface water.  For these reasons, despite their simple mineralogy, they have a reputation for being difficult to understand and many clastic sedimentologists approach them with caution!

Nevertheless, carbonate sedimentary rocks are important for many reasons.  They have been exploited for millenia for their minerals, water resources and, more recently, for cement, roadstone and hydrocarbon.  Now, as we face the effects of climate change, we can use carbonate strata to understand how Earth responds to environmental stress and use this knowledge to better predict the effect of climate change on modern ecosystems.  There is also growing interest in how carbonate sedimentary rocks can be used to good effect for carbon storage and geothermal heat production.  This talk will provide an introduction to carbonate sedimentology and the principle processes that govern their formation and modification during lithification.  It will illustrate their importance to our modern landscape and heritage and demonstrate how ancient carbonate systems can hold warnings, and solutions, to the effects of anthropogenic environmental impact.

Professor Cathy Hollis

Chair of Carbonate Geoscience

The University of Manchester, UK

cathy.hollis@manchester.ac.uk

Cathy Hollis a geologist with a particular interest in low temperature fluid-rock reactions, geochemistry and petrophysics in sedimentary rocks.  She is the research group lead for the Basins, Stratigraphy and Sedimentary Processes group in the Department of Earth and Environmental Science. She is also Adjunct Professor of Carbonate Geoscience at University of Bergen.  Her work focuses on the origin, evolution and occlusion of porosity in carbonate strata utilising outcrop, subsurface core and geophysical data alongside geochemical proxies. She is particularly interested in how limestones react and transform to dolomite and how minerals precipitate and dissolve from fluids in sedimentary basins.  Cathy is the principal investigator on a joint industry research consortium (PD3) with Universities of Bergen, Bristol and Liverpool, and collaborates with research groups in Canada, Qatar and France. She has extensive knowledge of the Lower Carboniferous Limestone of the UK, and she is leading a NERC funded project to assess the impact of hydrothermal karst on fluid flow. This work will be important to planning low-carbon, sustainable geothermal energy projects, which will be an essential part of our transition to net zero. Cathy has published over 45 papers in international, peer-reviewed journals in the last 10 years and graduated more than 15 PhD candidates in that time. She has a PhD from University of Aberdeen and prior to joining University of Manchester, in 2007, she worked for Badley Ashton and Associates Ltd in the UK and UAE (1995-2001) and Shell International Exploration and Production in The Netherlands (2001-2007).