Gail Ashley

Gail Ashley doing  fieldwork

Distinguished Professor, Geology

Research Interests
My research focuses on the geological record of the paleo environment, paleo climate and climate change in East Africa during last few million years. My particular interests are water resources available to hominins, Homo habilis, Paranthropus boisei and Homo erectus (Olduvai Gorge) and Holocene-age hunter-gatherers (Lake Turkana) and modern hunter-gatherers (Hazabe) at Lake Eyasi. I have been working in Tanzania and Kenya for over 25 years studying the sedimentary record of rivers, lakes, wetlands and springs associated with archaeological sites, as well as modern their analogs.

Current Projects
I am member of TOPPP (The Olduvai Paleontological and Paleoecology Project) where I focus on the paleo groundwater records of springs and wetlands, paleosols and playa lakes. I collaborate with paleobotanist Doris Barboni (CEREGE, FR) and organic geochemist Clayton Magill (Heriot- Watt, UK).

I collaborate with sedimentary geochemist Daniel Deocampo (Georgia State Univ.) on a NSF-funded project (ACACIA) using clay mineral composition to track paleoclimate change in East Africa, specifically aridity cycles.

I am working with hydrogeologist and modeler Mark Cuthbert (Cardiff, UK) studying the modern surface and groundwater hydrology in the volcanic Highlands, Ngorongoro Conservation Area. We are using modern systems as an analog for the paleo springs and wetlands associated with archaeological sites.

Selected Publications
2017, Ashley, G.M., Ndiema, E.K., Spencer, J.Q.G., Harris, J.W.K., Kiura, P.W., Dibble, Du, A., Lordan, P.T., Paleoenvironmental reconstruction of Dongodien, Lake Turkana, Kenya and OSL dating of site occupation during Late Holocene climate change. African Archaeology Review, DOI 10.1007/s10437-017-9260-4

2017 Arráiz H., Barboni D., Ashley G.M., Uribelarrea D., Mabulla A, Baquedano E., Domínguez-Rodrigo M.. The FLK Zinj paleolandscape: reconstruction of a 1.84 Ma wooded habitat in the FLK Zinj-AMK-PTK-DS archaeological complex, Middle Bed I (Olduvai Gorge, Tanzania). Paleoecology, Paleogeography, Paleoclimatology, Olduvai Gorge Paleoecology-Special Issue doi: 10.1016\J.Palaeo.2017.02.036

2017, M.O. Cuthbert, T. Gleeson, S.C. Reynolds, M.R. Bennett, A.C. Newton, C.J. McCormack & G.M. Ashley, Modelling the role of groundwater hydro-refugia in East African hominin evolution and dispersal, Nature Communications 8:15696 |doi. 10.1038/ncomms15696: 696

2017, Deocampo, D.M., Berry, P.A., Beverly, E.J., Ashley, G.M., Jarrett, R.E., Precessional climate control in East Africa ~1.95-1.75 million years ago, Olduvai Gorge, Tanzania: a geochemical record of lacustrine authigenic clays. GEOLOGY, 45(8), 683-686. doi:10.1130/G38950.1

2017, Goman, M., Ashley, G.M., Owen, R.B., Hover, V.C., Maharjan, D. K., Late Holocene envir-onmental reconstruction from groundwater-fed wetlands of Lake Solai, Kenya. The Professional Geographer, V. 69(3), p. 438-454.

2016, Magill, C.R., Ashley, G.M., Dominguez-Rodrigo, M., and Freeman, K.H., Dietary Options and Behavior Suggested by Plant Biomarker Evidence in an Early Human Habitat, Proceedings of the National Academy. 113(8)

2016, Ashley, G.M., de Wet, C.B., Barboni, D., Magill, C.R. Subtle signatures of seeps: Record of   groundwater in a dryland, DK, Olduvai Gorge, Tanzania. The Depositional Record, Wiley, doi: 10.1002/dep2.11.

 2016, Driese, S.G., and Ashley, G.M., Paleoenvironmental reconstruction of a paleosol catena, the Zinj archaeological level, Olduvai Gorge, Tanzania: Quaternary Research, 85(1), 133-146. 85doi:10.1016/j.yqres.2015.10.007. 

2014, Cuthbert, M.O. and Ashley, G.M., A spring forward for hominin evolution in East Africa. PLOS ONE 9(9): e107358. doi:10.1371/journal.pone.0107358.

2014, Ashley, G.M., de Wet, C.B., Domínguez-Rodrigo, M., Karis, A.M. O’Reilly, T.M., Baluyot, R.D. Freshwater limestone in an arid rift basin: a Goldilocks effect. Journal of Sedimentary Research. 84:988-1004.

2014, Ashley, G.M. “Spring Settings”, Contribution to Encyclopedia of Geoarchaeology, Springer, Heidelberg, Germany.

2014, Ashley, G.M, Bunn, H.T., Delaney, J.S., Barboni, D., Domínguez-Rodrigo, M., Mabulla, A.Z.P., Gurtov, A.N., Baluyot, R.D., Beverly, E.J., Baquedano, E., Paleoclimate and paleoenvironmental framework of FLK North archaeological site, Olduvai Gorge, Tanzania. Quaternary International, 322-323: 54-65.

2014, Ashley, G.M., Beverly, E.J., Sikes, N.E., Driese, S.G. Paleosol diversity in the Olduvai   Basin, Tanzania: effects of geomorphology, parent material, depositional environment, and       groundwater on soil development. Quaternary International, 322-323:66-77.

2013, Ashley, G.M., Deocampo, D.M., Kahmann-Robinson, J., Driese, S.G. Groundwater-fed wetland sediments and paleosols: It’s all about water table. In New Frontiers in Paleopedology and Terrestrial Paleoclimatology: Paleosols and Soil Surface Analog Systems SEPM Special Publication No. 104:47-61.

2012, Magill, C.R., Ashley, G.M., and Freeman, K.H., Ecosystem variability and early human habitats in eastern Africa, Proceedings of National Acadeny of Sciences,

2012, Magill, C.R., Ashley, G.M., and Freeman, K.H., Water, plants, and early human habitats in eastern Africa. Proceedings of National Acadeny of Sciences,

2012 Domínguez-Rodrigo Manuel, Travis Rayne Pickering, Fernando Diez-Martín, Audax Mabulla, Charles Musiba, Gonzalo Trancho, Enrique Baquedano, Henry T. Bunn, Doris Barboni, Manuel Santonja, David Uribelarrea, Gail M. Ashley, María del Sol Martínez-Ávila, Rebeca Barba, Agness Gidna, José Yravedra, Carmen Arriaza1, Earliest Porotic Hyperostosis on a 1.5-Million-Year-Old Hominin, Olduvai Gorge, Tanzania: Plos One

2011, Ashley, G.M., Ndiema, E., Harris, J. W. K., Kiura, P.W., and Spencer, J.Q.G. Paleoenvironmental context of archaeological sites, implications for subsistence strategies under Holocene climate change, northern Kenya. Geoarchaeology, International Journal, 26(6), 809-837.

2010, Ashley, G.M, Barboni, D., Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P., Diez-Martin F., Barba, R. and Baquedano, E. A spring and wooded habitat at FLK Zinj and their relevance to origins of human behavior, Quaternary Research, 74:304-314

2010, Ashley, G.M, Barboni, D., Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P, Diez-Martin F., Barba, R. and Baquedano, E., Paleoenvironmental and paleoecological reconstruction of a freshwater oasis in savannah grassland at FLK North, Olduvai Gorge, Tanzania, Quaternary Research, 74: 333-343.

2010, Barboni, D., Ashley, G.M, Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P, and Baquedano, E. Phytoliths infer locally dense and heterogeneous paleovegetation at FLK North and surrounding localities during upper Bed I time, Olduvai Gorge, Tanzania, Quaternary Research, 74:344-354.

2010, Domínguez-Rodrigo, Bunn, H.T., Mabulla, A.Z.P, Ashley, G.M., Diez-Martin F., Barboni, D., Prenderrgast, M.E., Yravedra, J., Barba, R., Sanchez, A., Baquedano, E., and Pickering, T.R. New excavations at the FLK Zinjanthrous site and its surroundings landscape and their behavioral implications. Quaternary Research, 74:315-332.

2010, Ashley, G. M., Domínguez-Rodrigo, Manuel, Bunn, Henry T., Mabulla, Audax Z.P., and Baquedano, Enrique, Sedimentary Geology and Human Origins: A Fresh Look At Olduvai Gorge, Tanzania. Journal of Sedimentary Research, 80: 703-709.

2010, Domínguez-Rodrigo, M, Mabulla, A.Z.P., Bunn, H.T., Diez-Martin, F., Barboni, D., Barba, R., Domenguez-Solera, P., Ashley, G.M., Baquedano, E., Yravedra, J., Disentangling hominin and carnivore activities near a spring at FLK North (Olduvai Gorge, Tanzania). Quaternary Research, 74:363-375.

2010, Bunn, H.T., Mabulla, A.Z.P., Domínguez-Rodrigo, M., Ashley, G.M., Barba, R., Diez-Martín, F., Remer, K., Yravedra, J., Baquedano, E., Was FLK North levels 1–2 a classic “living floor” of Oldowan hominins or a taphonomically complex palimpsest dominated by large carnivore feeding behavior? Quaternary Research, 74:355-362.

2009, Ashley, G.M., Tactikos, J.C. and Owen, R.B. Hominin use of springs and wetlands: paleoclimate and archaeological records from Olduvai Gorge (1.79-174 Ma). Palaeogeography, Palaeoclimatology, Palaeoecology, 272:1-16.

2009, Johnson Roure, C., Ashley, G.M., de Wet, C.B., Dvoretsky, R., Park, L. Hover, V.C., Owen, R.B., McBrearty, S., 2009, Tufa as a record of perennial freshwater in semi-arid rift basin, Kapthurin Formation, Central Kenya. Sedimentology, 56:1115-1137.

2008, Ashley, G.M., Human Evolution and Climate Change. In V. Gornitz (ed.) Encyclopedia of Paleoclimatology and Ancient Environments, Dordrecht, The Netherlands, Kluwer Academic Publishers, p. 446-450.

2007, Ashley, G.M. Orbital rhythms, monsoons, and playa lake response, Olduvai Basin, equatorial East Africa (~1.85-1.75), Geology, 35:1091-1094.

2007, Sikes, N.E. and Ashley, G.M., Stable isotopic signatures of pedogenic carbonates as indicators of paleoecology in the Plio-Pleistocene (upper Bed I) western margin of Olduvai Basin, Tanzania. In, African Paleoclimate and Human Evolution (M. Maslin and B. Christiansen, eds.), Journal of Human Evolution, v.53/5 pp 574-594.

2005, Liutkus, C.M., Wright, J.D., Ashley, G.M., and N.E. Sikes, Paleoenvironmental interpretation of lake-margin deposits using d13C and d18O results from Early Pleistocene carbonate rhizoliths, Olduvai Gorge, Tanzania. GEOLOGY, v. 33, p. 377-380.

2004, Ashley, G.M. , Maitima Mworia, J.M., Muasya, A.M., Owen, R.B., Driese, S.G., Hover, Renaut,R.W., Goman, M.F., Mathai, S. and Blatt, S.H. Sedimentation and evolution of a freshwater wetland in a semi-arid environment, Loboi Swamp, Kenya, East Africa. Sedimentology, 51:1-21.

2004, Driese, S.G., Ashley, G.M., Li, Z-H., Hover, V.C., and Owen, R.B., Micromorphology, geochemistry, and stable carbon isotopes of late Holocene wetland and floodplain soils, Loboi Plain, Kenya: wetland pedogenesis in a semi-arid setting. Palaeogeography, Paleoclimatology, Palaeoecology, v. 213, p. 231-250.  

2004, Owen, R.B., Renaut, R.W., Hover, V.C., Ashley, G.M., and Muasya, A.M. Swamps, springs, and diatoms: wetlands regions of the semi-arid Bogoria-Baringo rift, Kenya. Hydrobiologia, . 518 (1-3):59-78.

2003, Hover, V.C. and Ashley, G.M., Geochemical signatures of paleodepositional and diagenetic environments: a STEM/AEM study of authigenic clay minerals from an arid rift basin, Olduvai Gorge, Tanzania. Clays and Clay Minerals. 51:231-251.

2003, Liutkus, C.M. and Ashley, G.M., Facies model of a semi-arid freshwater wetland, Olduvai Gorge, Tanzania, Journal of Sedimentary Research. 73(5):691-795.

2003, Blumenschine, R.J., Peters, C.R., Masao, F.T., Clarke, R.J., Deino, A.L., Hay, R.L., Swisher, C.C., Stanistreet, I.G., Ashley, G.M., McHenry, L.J., Sikes, N.E., van der Merwe, N.J., Tactikos, J.C., Cushing, A.E., Deocampo, D.M., Njau, J.K., Ebert, J.I., 2002, Lake Pliocene Homo and hominid land use from western Olduvai Gorge, Tanzania. Science, 299:1217-1221.

2002, Ashley, G.M. and Liutkus, C.M., Tracks, trails and trampling by large vertebrates in a rift valley paleo-wetland, lowermost Bed II, Olduvai Gorge, Tanzania. Ichnos, 9:23-32.

2002, Ashley, G.M., Goman, M., Hover, V.C., Owen, R.B., Renaut, R.W. and Muasya, A.M., Artesian blister wetlands, a perennial water resource in the semi-arid rift valley of East Africa. Wetlands, 22(4):686-695.

2002, Ashley, G.M. and Hay R.L., Sedimentation patterns in an Plio-Pleistocene volcaniclastic rift-margin basin, Olduvai Gorge, Tanzania. In Sedimentation in Continental Rifts, SEPM Special Publication 73, p. 107-122.

2002, Deocampo, D.M., Blumenschine, R.J., and Ashley, G.M., Freshwater wetland diagenesis, fossil vertebrates, and traces of early hominids in the lowermost Bed II (~ 1.8 myr) playa lake-margin at Olduvai Gorge, Tanzania. Quaternary Research, v. 57, p. 271-281.

2001, Ashley, G.M., Archaeological sediments in springs and wetlands. In Stein, J.K. and Farrand, W.R., eds., Sediments in Archaeological Contexts, Salt Lake City, University of Utah Press, p. 183-210.

2000, Ashley, G.M. and Driese, S.G., Paleopedology and paleohydrology of a volcaniclastic paleosol interval: implications for early Pleistocene stratigraphy and paleoclimate record, Olduvai Gorge, Tanzania. Journal of Sedimentary Research, v. 70, n. 5 p.1065-1080.

2000, Ashley, G.M. Geologists probe hominid environments, GSA Today. v.10, n.2, p. 24-29.