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Department of Earth Sciences

Clay Mineralogy
Planetary Geology


2010-2014: MSci. Geology., Imperial College London

2014-2018: Ph.D. University of Cambridge 

2018-2020: Postdoctoral researcher (European Research Council), Utrecht University

2020-2021: Postdoctoral researcher (European Research Council), University of Hull

2021-2024 : Postdoctoral researcher (Natural Environment Research Council), University of Cambridge

2024-2025: Postdoctoral researcher (Leverhulme Centre for Life in the Universe), University of Cambridge

2021-        : Research Fellow., Clare Hall, University of Cambridge




No other minerals attract as great an interest as clays. Being formed from different weathered rocks under immensely variable conditions, clays differ in both mineral type and origin. Whilst techniques to separate clay assemblages by mineral type are widely established, criteria to differentiate clay minerals of varying origin have only recently been achieved. This is in part thanks to a new generation of electron imaging and mapping tools, optimized for the analysis of fine-grained minerals. This key breakthrough now promises to revolutionise the study of Earth’s most commonly available geo-material.

I am utilizing advances in electron microscopy, and the establishment of criteria to separate clay assemblages within mudrocks, to: 1) understand how rock weathering has changed across geological timescales as a consequence of biological evolution; and 2) consider how temporal variabilities in the availability of clay has impacted life’s early fossil record.

Martian sedimentary rocks (interview on Fox News):

Earth's earliest forest (article on BBC News):

Largest ever millipede fossil (article on BBC News):

Ediacaran life (interview on Evolution Soup):

The search for life on Mars (interview on The Naked Scientists):


Google Scholar:



Key publications: 

32) Davies, N.S., McMahon, W.J., Berry, C.M. Earth’s earliest forest: fossilized trees and vegetation-induced sedimentary structures from the Eifelian Hangman Sandstone Formation, Somerset and Devon, SW England. Journal of the Geological Society (in press)

31) Davies, N.S., McMahon, W.J., Shillito, A.P., Veenma, Y.P., Craig, J.A. Ichnology of a Middle Devonian regression: Environment, terrestrialization and true substrate controls on trace fossils of the Hangman Sandstone Formation, SW England Palaeogeography, Palaeoclimatology, Palaeoecology, p. 111671

30) Veenma, Y.P., Davies, N.S., Higgs, K.T., McMahon, W.J. Biogeomorphology of Ireland’s oldest fossil forest: Plant-sediment and plant-animal interactions recorded in the Late Devonian Harrylock Formation, Co. Wexford. Palaeogeography, Palaeoclimatology, Palaeoecology, 621, p. 111579

29) McMahon, W.J., Herron, S., Craig, J., Davies, N.S. Mud retention in hydrologically closed basins promoted pre-vegetation meandering: evidence from the Neoproterozoic Diabaig Formation, Scotland. Geological Society, London, Special Publications, 540

28) Mitchell, R.L., Kenrick, P., Pressel S., Duckett, J., Strullu-Derrien, C., Davies, N.S., McMahon, W.J., Summerfield, R. Terrestrial surface stabilization by modern analogues of the earliest land plants: a multi-dimensional imaging study. Geobiology, 21. 454-473

27) Kleinhans, M.G., McMahon, W.J., Davies, N.S. What event is a meandering river? A philisophical review of multi-level causes and systemic interaction contributing to river meandering. Geological Society, London, Spec. Pub. 540.

26) McMahon, W.J., Davies, N.S., Kleinhans, M.G., Mitchell, R.L. Paleozoic vegetation increased fine sediment in fluvial and tidal channels: Evidence from secular changes to the mudrock content of ancient point bars. Geology, 51, 136-140

25) Shillito, A.P., Davies, N.S., McMahon, W.J., Slater B.J. Deep time biogeomorphology 2: Animals as ancient ecosystem engineers. Palaios, 12, 701-702

24) Han, S., Loehr, S.C., Abbott, A.N., Baldermann, A., Farkas, J., McMahon, W.J., Milliken, K.L., Rafiei, M., Wheeler, C., Owen, M. Earth System Science applications of next-generation SEM-EDS automated mineral mapping. Frontiers in Earth Science, 10, 2244

23) Spencer, C., Davies, N.S., Gernon, T.M., Wang, X., McMahon, W.J., Rae Morrell, T., Hincks, T., Puhfal, P.K., Brasier, A., Seraine, N., Lu, G. Evolution of land plants changed the composition of the continental crust. Nature Geoscience 15, 735-740

22) Davies, N.S., McMahon, W.J., Shillito, A.P., Slater, B.J. Deep time biogeomorphology: The co-evolution of life and sediments. Palaios, 37, 219-223 

21) McMahon, W.J., Pierik, H.J., Shillito, A.S., Salese, F., Van Der Kwaak, B., Parsons, D.R., Kleinhans, M.G. Superimposed climatic and biological controls on siliciclastic architecture: An Early Mississippian (Visean) example from tropical Laurussia. Palaios, 37, 224-250

20) McMahon, W.J., Davies, N.S., Liu, A.G., Went, D.J. Enigma variations: characteristics and likely origin of the problematic surface texture Arumberia as recognized from an exceptional bedding plane exposure and the global record. Geological Magazine, 159, 1-20

19) Davies, N.S., Garwood, R., McMahon, W.J., Schneider, J., Shillito, A.S. The largest arthropod in Earth history: Insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England). Journal of the Geological Society, 179.

18) Brückner, M.Z.M., McMahon, W.J., Kleinhans, M.G. Muddying the waters: Modelling the effects of early land plants in Paleozoic estuaries. Palaios , 36, 173-181

17) Davies, N.S., McMahon, W.J. (2021) Land plant evolution and global erosion rates. Chemical Geology, 120128

16) McMahon, W.J., Liu, A.G., Tindal, B., Kleinhans, M.G. (2020) Ediacaran life close to land: Coastal and shoreface habitats of the Ediacaran macrobiota, the central Ikara-Flinders Ranges, South Australia. Journal of Sedimentary Research, 90, 1463-1499

15) Terwisscha van Scheltinga, R.C., McMahon. W.J., van Dijk. W.M., Eggenhuisen, J.T., Kleinhans. M.G. (2020) Experimental distributive fluvial systems: Bridging the gap between river and rock record. The Depositional Record, 6, 670-684

14) Salese, F*., McMahon, W.J*., Balme, M., Ansan, V., Davis, J., Kleinhans, M. (2020) Sustained fluvial deposition recorded in Mars’ Noachian stratigraphic record. Nature Communications, 11, 1-8 (*contributed equally)

13) Salese, F., Kleinhans, M.G., Mangold, N., Ansan, V., McMahon, W.J., Haas, T., Dromart, G. (2020) Estimated minimum lifespan of the Jezero Fluvial delta (Mars). Astrobiology, 20, 977-993

12) McMahon, W.J., Davies, N.S. (2020) Physical and biological functioning in Proterozoic rivers: evidence from the archetypal pre-vegetation alluvium of the Torridon Group, NW Scotland. Scottish Journal of Geology, 56, 1-29

11) Davies, N.S., Slater, B.J., Shillito, A.P., Liu, A.G., McMahon, W.J. (2020) Evolutionary synchrony of Earth’s biosphere and sedimentary-stratigraphic record. Earth-Science Reviews 102979 2019

10) Davies, N.S., Shillito, A.P., McMahon, W.J. (2019) Where does the time go? Assessing the chronostratigraphic fidelity of sedimentary rock outcrops. Journal of the Geological Society 176, 1154-1168

9) Balme, M.R., Curtis-Rouse, M.C., McMahon, W.J., (53 authors). (2019) The UK Space Agency Mars Utah Rover Field Investigation (MURFI). Planetary and Space Science, 165, 31-56 2018

8) McMahon, W.J., Davies, N.S. (2018) The shortage of geological evidence for pre-vegetation meandering rivers. In: Ghinnasi, M. et al. (eds.) ‘Fluvial meanders and their sedimentary products in the rock record’ IAS Special Publication 48, 119-148

7) McMahon, W.J., Davies, N.S. (2018) Evolution of alluvial mudrock forced by early land plants. Science, 359, 1022-1024

6) McMahon, W.J., Davies, N.S. (2018) High-energy flood events recorded in the Mesoproterozoic Meall Dearg Formation, NW Scotland; their recognition and implications for the study of pre-vegetation alluvium. Journal of the Geological Society175, 13-32

5) Went, D.J., McMahon, W.J. (2018) Fluvial products and processes before the evolution of land plants: evidence from the Lower Cambrian Series Rouge, English Channel Region. Sedimentology65, 2559-2594

4) Davies, N.S., McMahon, W.J., Shilito, A.P. (2018) A graphic method for depicting horizontal direction data on vertical outcrop photographs. Journal of Sedimentary Research, 88, 516-521 2017

3) Davies, N.S., Shilito, A.P., McMahon, W.J. (2017) Short-term evolution of primary sedimentary surface textures (microbial, abiotic, ichnological) on a dry stream bed: modern observations and ancient implications. Palaios, 32, 125-134

2) Davies, N.S., Gibling, M.R., McMahon, W.J., Slater, B.J., Long, D.G.F., Bashforth, A.R., Berry, C.M., Falcon-Lang, H.J., Gupta, S., Rygel, M.C., Wellman, C.H. (2017) Discussion on ‘Tectonic and environmental controls on Palaeozoic fluvial environments: reassessing the impacts of early land plants on sedimentation’. Journal of the Geological Society, 174, 947-950

1) McMahon, W.J., Davies, N.S., Went, D.J. (2017) Negligible microbial matground influence on pre-vegetation river functioning: Evidence from the Ediacaran-Lower Cambrian Series Rouge, France. Precambrian Research, 292, 13-34.

Postdoctoral Research Associate
Research Fellow, Clare Hall

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