Emeritus Faculty Members

Emeritus/Distinguished Professor

Director of Quaternary Studies Program

Lab. Room 269 848-445-3488

Education

• B.S., M.S., University of Massachusetts
• Ph.D., University of British Columbia

Teaching

• Undergraduate: Sedimentary Geology, Geomorphology, Planet Mars
• Graduate: Sedimentology of Rift Basins; Facies Models; Rift Basins, Structure & Fill

Research Interests

East African Research - [Link]

My research is focused on the Quaternary epoch, a time of rapid climate change. I study modern physical processes and deposits of glacial, fluvial, lacustrine, arid landscapes, and use this information to interpret paleoenvironments.

I have three ongoing projects: (1) reconstruction of paleoenvironments and paleoclimate history in the East African rift valley (Tanzania and Kenya); (2) interpretation of modern, Holocene and Pleistocene rift valley groundwater discharge records (spring, seeps and wetlands); (3) application of the Critical Zone concept to deep time.

"A freshwater carbonate deposit was found associated with hominin remains suggesting use of spring water at Olduvai Gorge"

"Freshwater wetlands on the Loboi Plain, Lake Bogoria, Kenya"

Publications

• Ashley, G.M., Ndiema, E., Spencer, J.Q.G., Du, A., Lordan, P.T., Kiura, P.W., Dibble, L., Harris, J.W.K., 2017, Paleoenvironmental reconstruction of Dongodien, Lake Turkana, Kenya and OSL dating of site occupation during Late Holocene climate change, African Archaeological Review. DOI 10.1007/s10437-017-9260-4
• Arráiz H., Barboni D., Ashley G.M., Uribelarrea D., Mabulla A, Baquedano E., Domínguez-Rodrigo M., 2017, 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
• Cuthbert, M.O., T. Gleeson, T., Reynolds, S.C., Bennett, M.R., Newton, A.C., McCormack, C.J., Ashley, G.M., 2017, Modelling the role of groundwater hydro-refugia in East African hominin evolution and dispersal, Nature Communications. 8:15696 |DOI 10.1038/ncomms15696
• Deocampo, D.M., Berry, P.A., Beverly, E.J., Ashley, G.M., Jarrett, R.E., 2017, Precessional climate control in East Africa ~1.95-1.75 million years ago, Olduvai Gorge, Tanzania: a geochemical record of lacustrine authigenic clays. GEOLOGY. DOI:10.1130/G38950.1
• Goman, M., Ashley, G.M., Owen, R.B., Hover, V.C., Maharjan, D. K., 2017, Late Holocene envir-onmental reconstruction from groundwater-fed wetlands of Lake Solai, Kenya. The Professional Geographer, V. 69(3), p. 438-454. doi.org/10.1080/00330124.2016.1266948.
• Magill, C.R., Ashley, G.M., Dominguez-Rodrigo, M., Freeman, K.H., 2016, Dietary Options and Behavior Suggested by Plant Biomarker Evidence in an Early Human Habitats, Proceedings of the National Academy. 113(8) www.pnas.org/cgi/doi/10.1073/pnas. 1507055113
• Ashley, G.M., de Wet, C.B., Barboni, D., Magill, C.R., 2016, Subtle signatures of seeps: Record of   groundwater in a dryland, DK, Olduvai Gorge, Tanzania. The Depositional Record. Wiley, doi: 10.1002/dep2.11.
• Driese, S.G., and Ashley, G.M., 2016, 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.
• Cuthbert, M.O. and Ashley, G.M., 2014, A spring forward for hominin evolution in East Africa. PLOS ONE 9(9): e107358. doi:10.1371/journal.pone.0107358.
• Ashley, G.M., de Wet, C.B., Domínguez-Rodrigo, M., Karis, A.M. O’Reilly, T.M., Baluyot, R.D. 2014, Freshwater limestone in an arid rift basin: a Goldilocks effect. Journal of Sedimentary Research. 84:988-1004.
• Ashley, G.M. “Spring Settings”, 2014, Contribution to Encyclopedia of Geoarchaeology, Springer, Heidelberg, Germany.
• 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., 2014, Paleoclimate and paleoenvironmental framework of FLK North archaeological site, Olduvai Gorge, Tanzania. Quaternary International. 322-323: 54-65.
• Beverly, E.J., Ashley, G.M., Driese, S.G., 2014, Reconstruction of a Pleistocene paleocatenas using micromorphology and geochemistry of lake margin paleo-Vertisols, Olduvai Gorge, Tanzania. Quaternary International. 322-323: 78-94.
• Ashley, G.M., Beverly, E.J., Sikes, N.E., Driese, S.G., 2014, 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.
• Ashley, G.M., Deocampo, D.M., Kahmann-Robinson, J., Driese, S.G., 2013, 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.
• Magill, C.R., Ashley, G.M., Freeman, K.H., 2012, Ecosystem variability and early human habitats in eastern Africa, Proceedings of National Acadeny of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1206276110
• Magill, C.R., Ashley, G.M., Freeman, K.H., 2012, Water, plants, and early human habitats in eastern Africa. Proceedings of National Acadeny of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1209405109
• Domínguez-Rodrigo, M., Pickering, T.R., Diez-Martín, F., Mabulla, A., Musiba, C., Trancho, G.,Baquedano, E., Bunn, H.T., Barboni, D., Santonja, M., Uribelarrea, D., Ashley, G.M., Sol Martínez-Ávila, M., Barba, R., Gidna, A., Yravedra, J., Arriaza1, C. 2012, Earliest Porotic Hyperostosis on a 1.5-Million-Year-Old Hominin, Olduvai Gorge, Tanzania: Plos One. https://doi.org/10.1371/journal.pone.0046414
• Domínguez-Rodrigo, M., Bunn, H.T., Pickering, T.R., Mabulla, A.Z.P., Musiba, C.M., Baquedano, E., Ashley, G.M., Diez-Martin, F., Santonja, M.. Uribelarrea, D., Barba, R., Yravedra, J., Barboni, D., Arriaza, C., Gidna, A., 2012, Autochthony and orientation patterns in Olduvai Bed I: A re-examination of the status of post-depositional biasing of archaeological assemblages from FLK north (FLKN). Journal of Archaeological Science. 39(7):2116-2127.
• Dyar, M.D., Carmosino, M.L., Tucker, J.M. Brown, E.A., Clegg, S.M., Wiens, R.C., Barefield, J.E., Delaney, J.S., Ashley, G.M., Driese, S.G.,2012, Remote laser-induced breakdown spectroscopy analysis of East African Rift sedimentary samples under Mars conditions. Chemical Geology, 294-295: 135-151.
• Ashley, G.M., Ndiema, E., Harris, J. W. K., Kiura, P.W., and Spencer, J.Q.G., 2011, Paleoenvironmental context of archaeological sites, implications for subsistence strategies under Holocene climate change, northern Kenya. Geoarchaeology, International Journal. 26(6):809-837.
• Ashley, G.M, Barboni, D., Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P., Diez-Martin F., Barba, R. and Baquedano, E.,2010, A spring and wooded habitat at FLK Zinj and their relevance to origins of human behavior, Quaternary Research. 74:304-314.
• Ashley, G.M, Barboni, D., Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P, Diez-Martin F., Barba, R. and Baquedano, E.,2010, Paleoenvironmental and paleoecological reconstruction of a freshwater oasis in savannah grassland at FLK North, Olduvai Gorge, Tanzania, Quaternary Research. 74: 333-343.
• Barboni, D., Ashley, G.M, Domínguez-Rodrigo, M., Bunn, H.T., Mabulla, A.Z.P, and Baquedano, E., 2010, 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.
• Domínguez-Rodrigo, Bunn, H.T., Mabulla, A.Z.P, Ashley, G.M., Diez-Martin F., Barboni, D., Prendergast, M.E., Yravedra, J., Barba, R., Sanchez, A., Baquedano, E., and Pickering, T.R., 2010, New excavations at the FLK Zinjanthrous site and its surroundings landscape and their behavioral implications. Quaternary Research. 74:315-332.
• Ashley, G. M., Domínguez-Rodrigo, M., Bunn, H. T., Mabulla, A.Z.P., and Baquedano, E., 2010, Sedimentary Geology and Human Origins: A Fresh Look at Olduvai Gorge, Tanzania. Journal of Sedimentary Research. 80: 703-709.
• 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. ,2010, Disentangling hominin and carnivore activities near a spring at FLK North (Olduvai Gorge, Tanzania). Quaternary Research. 74:363-375.
• Bunn, H.T., Mabulla, A.Z.P., Domínguez-Rodrigo, M., Ashley, G.M., Barba, R., Diez-Martín, F., Remer, K., Yravedra, J., Baquedano, E.,2010, 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.
• Ashley, G.M., Tactikos, J.C. ,Owen, R.B., 2009, Hominin use of springs and wetlands: paleoclimate and archaeological records from Olduvai Gorge (1.79-174 Ma). Palaeogeography, Palaeoclimatology, Palaeoecology. 272:1-16.
• Johnson Roure, C., Ashley, G.M., deWet, 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.
• Owen, R.A., Owen R.B., Renaut R.W., Scott, J.J., Jones, B., Ashley, G.M., 2008,  Mineralogy and origin of rhizoliths on the margins of saline, alkaline Lake Bogoria, Kenya Rift Valley. Sedimentary Geology. 203(1–2), 143–163.
• Ashley, G.M., 2008, Human Evolution and Climate Change. In V. Gornitz (ed.) Encyclopedia of Paleoclimatology and Ancient Environments, Dordrecht, The Netherlands, Kluwer Academic Publishers, 446-450.
• Ashley, G.M., 2007, Orbital rhythms, monsoons, and playa lake response, Olduvai Basin, equatorial East Africa (~1.85-1.75), GEOLOGY. 35:1091-1094.
• Sikes, N.E. and Ashley, G.M., 2007, 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: 574-594.
• Carey, J.S., Sheridan, R.E., Ashley, G.M.,Uptegrove, J., 2005, Glacially-influenced late Pleistocene stratigraphy of a passive margin: New Jersey’s Jersey’s record of the North American ice sheet: Marine Geology, 218:155-173.
• Liutkus, C.M., Wright, J.D., Ashley, G.M., N.E. Sikes, 2005, Paleoenvironmental interpretation of lake-margin deposits using d¹³C and d¹⁸O results from Early Pleistocene carbonate rhizoliths, Olduvai Gorge, Tanzania. GEOLOGY. 33:377-380.
• M. Muasya, V.C. Hover, G. M. Ashley, R. B. Owen, M. F. Goman, M. Kimeli, 2004, Diversity and distribution of macophytes in a freshwater wetland, Loboi Swamp (Rift Valley) Kenya. Journal of East African Natural History. 93:39-47.
• 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.,Blatt, S.H., 2004, Sedimentation and evolution of a freshwater wetland in a semi-arid environment, Loboi Swamp, Kenya, East Africa. Sedimentology. 51:1-21.
• Driese, S.G., Ashley, G.M., Li, Z-H., Hover, V.C., Owen, R.B., 2004, Micro-morphology, 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, 213:231-250. 
• Owen, R.B., Renaut, R.W., Hover, V.C., Ashley, G.M., Muasya, A.M., 2004, Swamps, springs, and diatoms: wetlands regions of the semi-arid Bogoria-Baringo rift, Kenya. Hydrobiologia.518(1-3):59-78.
• Hover, V.C. and Ashley, G.M., 2003, 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.

   

  Liutkus, C.M. and Ashley, G.M., 2003, Facies model of a semi-arid freshwater wetland, Olduvai Gorge, Tanzania, Journal of Sedimentary Research. 73(5), p. 691-795.
• 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., 2003, Lake Pliocene Homo and hominid land use from western Olduvai Gorge, Tanzania. Science. 299:1217-1221.
• Muasya, A.M., Ashley, G. M., Hover, V. C., Renaut, R. W., Owen, R. B., Goman, M., 2002, Vegetation on Artesian blister wetlands around Lake Bogoria. Nature East Africa. 32:1-7.
• Ashley, G.M. and Liutkus, C.M., 2002, Tracks, trails and trampling by large vertebrates in a rift valley paleo-wetland, lowermost Bed II, Olduvai Gorge, Tanzania. Ichnos. 9: 23-32.
• Ashley, G.M., Goman, M., Hover, V.C., Owen, R.B., Renaut, R.W.,Muasya, A.M., 2002, Artesian blister wetlands, a perennial water resource in the semi-arid rift valley of East Africa. Wetlands. 22(4):686-695.
• De Wet, C.B., Ashley, G.M., Kegel, D.P. MD, 2002, Biological clocks and tenure timetables: Restructuring the academic timeline, Electronic publication, Geological Society of America website. http://rock.geosociety.org/pubs/gsatoday/0211clocks/0211gsatodayclocks.htm
• Gaswirth, S.B., Ashley, G.M., Sheridan, R.E., 2002, Use of seismic stratigraphy to identify conduits for saltwater and pollutant intrusion, in the vicinity of Raritan Bay, New Jersey. Environmental and Engineering Geosciences. VIII (3), p. 209-218.
• Ashley, G.M. and Hay R.L., 2002, Sedimentation patterns in an Plio-Pleistocene volcaniclastic rift-margin basin, Olduvai Gorge, Tanzania. In Sedimentation in Continental Rifts, SEPM Special Publication 73.107-122.
• Ashley, G.M. and Renaut, R.W., 2002, Rift Sedimentation. In R.W. Renaut and G.M. Ashley, eds., Sedimentation in Continental Rifts, SEPM Special Publication 73.3-10.
• Stanford, S.D., Ashley, G.M., Russell, E.W.B., Brenner, G.J., 2002, Rates and patterns of late Cenozoic denudation in the northernmost Atlantic Coastal Plain and Piedmont. Geological Society of America Bulletin. 114:1422-1437.
• Deocampo, D.M., Blumenschine, R.J., Ashley, G.M., 2002, 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. 57:271-281.
• Ashley, G.M., 2001, 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.183-210.