Nicholas Tosca

Nicholas Tosca

Associate Professor of Sedimentary Geology

Research Profile

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.

Teaching Profile

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)
  • Aqueous Geochemistry (within the NERC Doctoral Training Programme, 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.

Tosca, N.J., Jiang, C.Z., Rasmussen, B., Muhling, J.R. (in review) Products of the iron cycle on the early Earth. In: Early Life on Earth and Oxidative Stress, Eds.: Valentine, J.S. and Fischer, W.W., Free Radical Biology and Medicine, Elsevier.


Jiang, C.Z. and Tosca, N.J. (2019) Fe(II)-carbonate precipitation kinetics and the chemistry of anoxic ferruginous seawater, Earth and Planetary Science Letters, 506, 231-242, doi: 10.1016/j.epsl.2018.11.010


McLennan, S.M., Grotzinger, J.P., Hurowitz, J.A., Tosca, N.J. (2019) The sedimentary cycle on early Mars, Annual Review of Earth and Planetary Sciences, 47, 91-118, doi: 10.1146/annurev-earth-053018-060332.


Rasmussen, B., Muhling, J.R., Tosca, N.J., Tsikos, H. (in review) Evidence for anoxic shallow oceans and rise of oxygenic photosynthesis after 2.45 Ga, Proceedings of the National Academy of Sciences.


Pruss, S.B., Tosca, N.J., Stark, C. (2018) Small shelly fossil preservation and the role of early diagenetic redox in the Early Triassic, Palaios, 33, 10, 441-450.


Tosca, N.J., Ahmed, I.A.M., Tutolo, B.M., Ashpitel, A., Hurowitz, J.A. (2018) Magnetite authigenesis and the warming of early Mars, Nature Geoscience, 11, 635-639, doi: 10.1038/s41561-018-0203-8.


Lin, C.Y., Turchyn, A.V., Steiner, S., Bots, P., Lampronti, G.I., Tosca, N.J. (2018) The role of microbial sulfate reduction in calcium carbonate polymorph selection, Geochimica et Cosmochimica Acta, 237, 184-204, doi: 10.1016/j.gca.2018.06.019.


Hindshaw, R., S., Tosca, N.J., Piotrowski, A.M., Tipper, E.T. (2018) Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard), Earth Surface Dynamics Discussions., 6, 141-161, doi: 10.5194/esurf-2017-55.


Anderson, R.P., Tosca, N.J., Gaines, R.R., Mongiardino Koch, N., Briggs, D.E.G. (2018) A mineralogical fingerprint for Burgess Shale-type carbonaceous fossilization, Geology, 46(4), 347-350.


Tutolo, B.M. and Tosca, N.J. (2018) Experimental examination of the Mg-silicate-carbonate system at ambient temperature: Implications for alkaline chemical sedimentation and lacustrine carbonate formation, Geochimica et Cosmochimica Acta, 225, 80-101.


Xu, W., Ruhl, M., Jenkyns, H.C., Leng, M.J., Huggett, J.M., Minisini, D., Ullmann, C.V., Riding, J.B., Weijers, J., Storm, M.S., Percival, L.M.E., Tosca, N.J., Idiz, E.F., Tegelaar, E.W., Hesselbo, S.P. (2018) Evolution of the Toarcian (Early Jurassic) carbon-cycle and global climatic controls on local sedimentary processes (Cardigan Bay Basin, UK), Earth and Planetary Science Letters, 484, 396-411.


Tutolo, B.M., Luhmann, A.J., Tosca, N.J., Seyfried, W.E. (2018) Serpentinization as a reactive transport process: The brucite silicification reaction, Earth and Planetary Science Letters, 484, 385-395.


Pruss, S.B., Dwyer, C.H., Smith, E.F., Macdonald, F.A. & Tosca, N.J., (2017) Phosphatized early Cambrian archaeocyaths and small shelly fossils (SSFs) of southwestern Mongolia, Palaeogeography, Palaeoclimatology, Palaeoecology, doi: 10.1016/j.palaeo.2017.07.002.


Cohen, P.A., Strauss, J.V., Rooney, A.D., Sharma, M. & Tosca, N.J., (2017) Controlled hydroxyapatite biomineralization in an ~810 million-year-old unicellular eukaryote, Science Advances, 3(6), p. e1700095.


Tosca, N.J., Guggenheim, S., and Pufahl, P.K. (2016) An authigenic origin for Precambrian greenalite: implications for iron formation and the chemistry of ancient seawater. Geological Society of America Bulletin, 128, 3-4, p.511-530, doi: 10.1130/B31339.1.


Tosca, N.J. (2016) Geochemical pathways to Mg-silicate formation. In: Magnesian clays: Characterization, origins and applications. AIPEA Special Publication Series, no. 2., Digilabs, pp. 283-330, ISBN: 978-88-7522-093-6.


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, London, Special Publication, 435, http://


Strauss, J.V., MacDonald, F.A., Halverson, G.P., Tosca, N.J., Schrag, D.P. and Knoll, A.H. (2015) Stratigraphic evolution of the Neoproterozoic Callison Lake Formation: Linking the break-up of Rodinia to the Islay carbon isotope excursion, American Journal of Science, 315(10), pp. 881-944.


Jeans, C.V. and Tosca, N.J., 2014, 7th Cambridge Diagenesis Conference 2011: An introduction, Clay Minerals, 49(2), pp. 125-6, doi: 10.1180/claymin.2014.049.2.00.


Jeans, C.V., Tosca, N.J., Hu, X.F. & Boreham, S., 2014, Clay mineral-grain size-calcite cement relationships in the Upper Cretaceous Chalk, UK: a preliminary investigation, Clay Minerals, 49(2), pp. 299-325, doi: 10.1180/claymin.2014.049.2.09.


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, doi: 0.1180/claymin.2014.049.2.03.


Johnston, D.T., Poulton, S.W., Tosca, N.J., O’Brien, T., Halverson, G.P., Schrag, D.P., and Macdonald, F.A. (2013) Searching for an oxygenation event in the fossiliferous Ediacaran of Northwestern Canada, Chemical Geology, 362, 273-286.


Kraus, R., Stewart, S., Newman, M., Milliken, R.E., Tosca, N.J. (2013) Uncertainties in the Shock Devolatilization of Hydrated Minerals: A Nontronite Case Study. Journal of Geophysical Research, 118, 10, 2137-2145, doi: 10.1002/jgre.20147.


Anderson, R.P., Fairchild, I.J., Tosca, N.J., Knoll, A.H. (2013) Microstructures in metasedimentary rocks from the Neoproterozoic Bonahaven Formation, Scotland: Microconcretions, microtektites, or microfossils? Precambrian Research, 233, 59-72, doi: 10.1016/j.precamres.2013.04.016.


French, K., Tosca, N.J., Cao, C., Summons, R.E. (2012) Diagenetic and detrital origin of the moretane anomalies in the Permian-Triassic boundary section at Meishan, South China. Geochimica et Cosmochimica Acta, 84, 104-125, doi: 10.1016/j.gca.2012.01.004.


Lamb, M.P., Grotzinger, J.P., Southard, J.B., Tosca, N.J. (2012) Were aqueous ripples on Mars formed by flowing brines? in Sedimentary Geology of Mars, SEPM Special Publication 102, 139-150.


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.


Hurowitz, J.A., Fischer, W.W., Tosca, N.J., Milliken, R.E. (2010) Origin of acidic surface waters and the evolution of atmospheric chemistry on early Mars. Nature Geoscience, 3, 5, 323-326, doi: 10.1038/NGEO831.


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.


Xu, W., Tosca, N.J., McLennan, S.M., Parise, J.B. (2009) Humidity-induced phase transitions of ferric sulphate minerals studied by in situ X-ray diffraction. American Mineralogist, 94, 1629-1637, doi: 10.2138/am.2009.3182.


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.


McCubbin, F.M., Tosca, N.J., Smirnov, A., Nekvasil, H., Steele, A., Fries, M., Lindsley, D.H. (2009) Hydrothermal jarosite and hematite in a pyroxene-hosted melt inclusion in martian meteorite MIL 03346: Implications for magmatic hydrothermal fluids on Mars. Geochimica et Cosmochimica Acta, 73, 4907-4917, doi: 10.1016/j.gca.2009.05.031.


Hurowitz, J.A., Tosca, N.J., Dyar, M.D. (2009) Acid production by FeSO4nH2O dissolution and implications for terrestrial and martian aquatic systems. American Mineralogist, 94, 409-414, doi: 10.2138/am.2009.3085.


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


Knoll, A.H., Jolliff, B.L., Farrand, W.H., Bell, J.F., Clark, B.C., Gellert, R., Golombek, M.P., Grotzinger, J.P., Herkenhoff, K.E., Johnson, J.R., McLennan, S.M., Morris, R.V., Squyres, S.W., Sullivan, R., Tosca, N.J., Yen, A.S., Learner, Z. (2008) Late diagenetic veneers, rinds, and fracture fill at Meridiani Planum, Mars. Journal of Geophysical Research – Planets. doi: 10.1029/2007JE002949


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.


Hurowitz, J.A., Tosca, N.J., McLennan, S.M., Schoonen, M.A.A. (2007) Production of hydrogen peroxide in martian and lunar soils. Earth and Planetary Science Letters, 255, 1-2, 41-52, doi: 10.1016/j.epsl.2006.12.004.


Squyres, S.W., and 53 others (including N.J. Tosca) (2006) Overview of the Opportunity Mars Exploration Rover Mission to Meridiani Planum: Eagle Crater to Purgatory Ripple. Journal of Geophysical Research – Planets, 111, E12, E12S12, doi: 10.1029/2006JE002771


Squyres, S.W., Knoll, A.H., Arvidson, R.E., Clark, B.C., Grotzinger, J.P., Jolliff, B.L., McLennan, S.M., Tosca, N.J., Bell III, J.F., Calvin, W.M., Farrand, W.H., Glotch, T.D., Golombek, M.P., Herkenhoff, K.E., Johnson, J.R., Klingelhoefer, G., McSween, H.Y., Yen, A.S. (2006) Two years at Meridiani Planum: Results from the Opportunity Rover. Science, 313, 5792, 1403 doi: 10.1126/science.1130890.


Squyres, S.W., Aharonson, O., Arvidson, R.E., Bell III, J.F., Christensen, P.R., Clark, B.C., Crisp, J.A., Farrand, W.H., Glotch, T., Golombek, M.P., Grant, J., Grotzinger, J., Herkenhoff, K.E., Johnson, J.R., Jolliff, B.L., Knoll, A.H., McLennan, S.M., McSween, H.Y., Moore, J.M., Rice, J.W., Tosca, N.J. (2006) Planetary Science: Bedrock Formation at Meridiani Planum. Nature, 443, E1-E2, doi:10.1038/nature05212.


Wang, A., Haskin, L.A., Squyres, S.W., Arvidson, R.E., Jolliff, B.L., Crumpler, L., Gellert, R., Schroeder, C., Herkenhoff, K., Hurowitz, J.A., Tosca, N.J., Farrand, W., Anderson, R.C. (2006) Sulfate deposition in subsurface regolith exposed in trenches at the plains traversed by the Spirit rover in Gusev Crater, Mars. Journal of Geophysical Research – Planets, 111, E02S17, doi: 10.1029/2005JE002513.


Wang, A., Korotev, R.L., Jolliff, B.L., Haskin, L.A., Crumpler, L., Farrand, W., Herkenhoff, K.E., de Souza, P., Kusack, A.G., Hurowitz, J.A., Tosca, N.J. (2006) Evidence of phyllosilicates in Wooly Patch, an altered rock encountered at West Spur, Columbia Hills by the Spirit rover in Gusev crater, Mars, Journal of Geophysical Research – Planets, 111, E02S16, doi: 10.1029/2005JE002516.


Hurowitz, J.A., McLennan, S.M., Tosca, N.J., Arvidson, R.E., Michalski, J.R., Ming, D.W., Schroeder, C., Squyres, S.W. (2006) In situ and experimental evidence for acidic weathering of rocks and soils on Mars, Journal of Geophysical Research – Planets, 111, E02S19, doi: 10.1029/2005JE002515.


Arvidson, R. E., and 60 others (including N.J. Tosca) (2006), Overview of the Spirit Mars Exploration Rover Mission to Gusev Crater: Landing Site to Backstay Rock in the Columbia Hills, Journal of Geophysical Research – Planets, 111, E02S01, doi: 10.1029/2005JE002499.


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.


Knoll, A.H., Carr, M.H., Clark, B.C., Des Marais, D.J., Farmer, J.D., Fischer, W.W., Grotzinger, J.P., Hayes, A., McLennan, S.M., Malin, M.C., Schroeder, C., Squyres, S.W., Tosca, N.J., Wdowiak, T. (2005) An astrobiological perspective on Meridiani Planum. Earth and Planetary Science Letters, 240, 1, 179-189, doi: 10.1016/j.epsl.2005.09.045.


Grotzinger, J.P., Bell, J.F., Calvin, W., Clark, B.C., Fike, D., Golombek, M., Greeley, R., Herkenhoff, K.E., Jolliff, B., Knoll, A.H., Malin, M., McLennan, S.M., Parker, T., Soderblom, L., Sohl-Dickstein, J.N., Squyres, S.W., Tosca, N.J., Watters, W. (2005) Stratigraphy, sedimentology and depositional environment of the Burns Formation, Meridiani Planum, Mars. Earth and Planetary Science Letters, 240, 1, 11-72, doi: 10.1016/j.epsl.2005.09.039.


Clark, B.C., McLennan, S.M., Morris, R.V., Gellert, R., Jolliff, B.L., Knoll, A.H., Lowenstein, T.K., Ming, D.W., Tosca, N.J., Christensen, P.R., Gorevan, S., Yen, A.S., Brückner, J., Calvin, W., Dreibus, G., Farrand, W., Klingelhöfer, G., Wänke, H., Zipfel, J., Bell, J.F., Squyres, S.W., Grotzinger, J.P., McSween, H.Y., Rieder, R., Herkenhoff, K.E. (2005) Chemistry and mineralogy of outcrops at Meridiani Planum. Earth and Planetary Science Letters, 240, 1, 73-94, doi: 10.1016/j.epsl.2005.09.040.


McLennan, S. M., and 31 others (including Tosca, N.J.) (2005) Provenance and diagenesis of the evaporite-bearing Burns formation, Meridiani Planum, Mars. Earth and Planetary Science Letters, 240, 1, 95-121, doi: 10.1016/j.epsl.2005.09.041.


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.


Yen, A., and 35 others (including Tosca, N.J.) (2005) An integrated view of the chemistry and mineralogy of Martian soils, Nature, 436, 7047, 49-54, doi: 10.1038/nature03637.


Crumpler, L., and 30 others (including Tosca, N.J.) (2005) MER geologic traverse by the Spirit Rover in the plains of Gusev Crater, Mars. Geology, 33, 10, 809-812, doi: 10.1130/G21673.1.


Haskin, L.A., and 29 others (including Tosca, N.J.) (2005) Water alteration of rocks and soils from the Spirit rover site in Gusev Crater, Nature, 436, 7047, 66-69, doi: 10.1038/nature03640.


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.