My research group focuses on understanding the co-evolution of life and environments through Earth’s early history. The periods of time most interesting to us encapsulate intervals of major geological, environmental, and/or biological change on the Earth, including the Neoarchaean/early Palaeoproterozoic, Neoproterozoic, and early Palaeozoic Eras. All of these witnessed transitions in the Earth system thought to have played a key role in shaping life on Earth, yet the connections between environment and biology are not well understood. To tackle these problems, we use laboratory experimentation and theoretical modelling to help us understand how climate and depositional setting influence bottom and porewater chemistry which, in turn, are archived as mineral products that entered ancient sediments. Ultimately, laboratory studies and modelling must be applied to the sedimentary record, and so the success of our research approach requires that we fully understand the origin of mineralogical, geochemical, and isotopic signals preserved in sedimentary rocks, and how they relate to depositional setting, diagenesis, and metamorphism. A common theme is to link geological, mineralogical, and geochemical studies of sedimentary successions to new information gained from experiments and modelling, providing fresh insight into palaeo-environmental evolution. In many ways, we operate both as an aqueous geochemistry laboratory and as a sedimentology laboratory.
We are also interested in the early evolution of sedimentary environments on Mars, and what they can tell us about whether or not physical and chemical conditions on that planet were ever supportive of microbial life as it is currently understood on Earth.
Lastly, developing an improved understanding of chemical sedimentation and/or diagenesis through time also provides critical information to the industrial sector, where knowing the processes that influence the deposition and distribution of natural resources is a top priority.
We are always looking for interested and talented students and researchers to join our group, so please contact me to enquire about available PhD or post-doctoral positions.
I currently teach:
- Sedimentary processes: the origin of sediments at the Earth’s surface (Second year)
- Diagenetic processes: from sediment to rock (Second year)
- Dorset field course (Second year)
- Major environmental change (Fourth year)
- Within the NERC Doctoral Training Programme (the Biodiversity and Dynamic Earth streams), a NERC-sponsored partnership to train PhD students to conduct multidisciplinary research in environmental sciences
I am also a Fellow and Earth Sciences Tutor at St. Peter’s College, one of the constituent colleges of the University of Oxford. As a tutor, I run and coordinate small group teaching sessions (tutorials) for Earth Sciences students at St. Peter’s and other colleges at Oxford.
I also participate in outreach events at primary/secondary schools and in the University of Oxford Christmas Science Lectures held annually for Year 9 students at UK state schools.
View Selected Publications
Tosca, N.J., Pruss, S.B., Strauss, J.V. (in review) A sedimentary fingerprint of oscillating redox through the Cambrian Period.
Tosca, N.J., Guggenheim, S., and Pufahl, P.K. (2015) An authigenic origin for Precambrian greenalite: implications for iron formation and the chemistry of ancient seawater. Geological Society of America Bulletin, doi: 10.1130/B31339.1.
Tosca, N.J. and Wright, V.P. (2015) Diagenetic pathways linked to labile Mg-clays in lacustrine carbonate reservoirs: A model for the origin of secondary porosity in the Cretaceous Pre-Salt Barra Velha Formation, offshore Brazil. Geological Society of London, Special Publication, 435, 1, doi: 10.1144/SP435.1.
Tosca, N.J. (2015) Geochemical pathways to Mg-silicate formation. In: M. Pozo & E. Galan, Eds., Magnesian clays: Characterization, origins and applications. AIPEA Educational Series, Pub. no. 2, Digilabs, Bari, Italy, p. 283-330.
Tosca, N.J. and Masterson, A. (2014) Chemical controls on incipient Mg-silicate crystallisation at 25oC: Implications for non-marine carbonate diagenesis, Clay Minerals, 49, 195-224.
Tosca, N.J., Macdonald, F.A., Strauss, J.V., Johnston, D.T., Knoll, A.H. (2011) Sedimentary talc in Neoproterozoic carbonate successions. Earth and Planetary Science Letters, 306, 11-22, doi: 10.1016/j.epsl.2011.03.041
Tosca, N.J., McLennan, S.M., Lamb, M., Grotzinger, J.P. (2011) Physico-chemical properties of martian brines. Journal of Geophysical Research, 116, E05004, doi: 10.1029/2010JE003700.
Tosca, N.J., Johnston, D.T., Mushegian, A., Rothman, D.H., Summons, R.E., Knoll, A.H. (2010) Organic carbon burial, clay mineralogy and redox evolution in Proterozoic oceans. Geochimica et Cosmochimica Acta, 74, 5, 1579-1592, doi: 10.1016/j.gca.2009.12.001.
Tosca, N.J. and Knoll, A.H. (2009) Juvenile chemical sediments and the long term persistence of water at the surface of Mars. Earth and Planetary Science Letters, 286, 3-4, 379-386, doi:10.1016/j.epsl.2009.07.004.
Tosca, N.J. and McLennan, S.M. (2009) Experimental constraints on the evaporation of partially oxidized acid-sulfate waters at the martian surface. Geochimica et Cosmochimica Acta, 73, 1205-1222, doi: 10.1016/j.gca.2008.11.015
Tosca, N.J., Knoll, A.H., McLennan, S.M. (2008) Water activity and the challenge for life on early Mars. Science, 320, 1204-1207, doi: 10.1126/science.1155432
Tosca, N.J., McLennan, S.M., Dyar, M.D., Sklute, E.C., Michel, F.M. (2008) Fe-oxidation processes at Meridiani Planum and implications for secondary Fe-mineralogy on Mars. Journal of Geophysical Research – Planets. 113, E05005, doi: 10.1029/2007JE003019
Tosca, N.J., Smirnov, A., McLennan, S.M. (2007) Application of the Pitzer Ion Interaction Model to Isopiestic Data for the Fe2(SO4)3-H2SO4-H2O System at 298.15K and 323.15K. Geochimica et Cosmochimica Acta, 71, 11, 2680-2698, doi: 10.1016/j.gca.2007.03.020.
Tosca, N.J. and McLennan, S.M. (2006) Chemical divides and evaporite mineral assemblages on Mars. Earth and Planetary Science Letters, 241, 1-2, 21-31, doi: 10.1016/j.epsl.2005.10.021.
Tosca, N.J., McLennan, S.M., Clark, B.C., Grotzinger, J.P., Hurowitz, J.A., Knoll, A.H., Schröder, C., Squyres, S.W. (2005) Geochemical Modeling of Evaporation Processes on Mars: Insight from the Sedimentary Record at Meridiani Planum. Earth and Planetary Science Letters, 240, 1, 122-148, doi: 10.1016/j.epsl.2005.09.042. Selected as one of the “Top 50 Cited Articles of EPSL from 2004-2007”
Tosca, N.J., McLennan, S.M., Lindsley, D.H., Schoonen, M.A.A. (2004) Acid-sulfate weathering of synthetic Martian basalt: The acid fog model revisited, Journal of Geophysical Research, 109, E05003, doi: 10.1029/2003JE002218.