Using uranium-series (²³⁰Th/U) dating of novel and conventional materials, Sharp investigates human biologic and behavioral evolution, paleoclimatic change, neotectonic rates, and the evolution of Pleistocene landscapes. For example, ²³⁰Th/U dating of cave carbonates from North America, Europe, Africa and Asia provides time axes for paleoclimate proxy records and archaeological sequences, ²³⁰Th/U dating of soil carbonates provides ages for alluvial landforms linked to glacial and neotectonic processes, and dating of corals from Pacific island archaeological contexts refines the timing of human expansion across the Pacific. Novel protocols developed at BGC use ²³⁰Th/U dating and C, N, and O isotopes of ostrich eggshells to investigate the timing, tempo and paleoenvironmental context of hominin biological and behavioral evolution over the past 500,000 years. There are opportunities for prospective graduate students and postdocs to become involved in these and other projects and inquiries are welcome.
Primary Areas of Research Interest
Human origins and archaeology
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Timing and tempo of hominin physical and cultural evolution in Africa and Europe
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Timescale of human expansion across the Pacific Ocean
²³⁰Th/U dating of a carbonate concretion (lower right) attached to a skull from Sima de los Huesos (Spain) provides an age of 430,000 years for early ancestors of the Neanderthals.
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Paleoclimate and paleoenvironments
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Quaternary paleoclimate proxy records
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Paleoenvironmental records for archaeological sites using C, N, and O isotopes of ratite eggshells
²³⁰Th/U dating of a cave carbonate from northern India that formed in the late 20th and early 21st centuries allows comparison of oxygen isotopes from the carbonate with instrumental observations, helping to calibrate ancient carbonate records of the Indian summer monsoon. (Right) Nitrogen isotopes of ratite (ostrich, emu) eggshells from archaeological sites in Africa, the Near East, and Australia can provide onsite paleo-precipitation records.
Faults, fault behavior and neotectonic rates
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Geologic slip rates on the southern San Andreas fault and other continental strike-slip fault systems
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Fault history recorded in coseismic calcite veins
²³⁰Th/U on soil carbonate was used to estimate the age of an offset Quaternary alluvial fan and determine the slip rate along a strand of the southern San Andreas fault (California). (Right) ²³⁰Th/U dating of carbonate that seals fractures on the Loma Blanca normal fault (New Mexico) provides a 400,000 year record of faulting.
Novel applications of ²³⁰Th/U dating
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Improving timescales for archaeological sequences via ²³⁰Th/U dating of ratite eggshells
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Dating Pleistocene landforms of climatic and tectonic significance using ²³⁰Th/U dating of soil carbonate
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Examining U-Th systematics of materials at sub-millimeter scales using laser ablation
A protocol developed at BGC uses ²³⁰Th/U dating of ostrich eggshells to provide reliable, precise ages for African archaeological sequences from the Middle and Later Stone Ages (about 300,000 to 30,000 years ago), a period of accelerating human behavioral innovation.
Selected Publications
Niespolo, E.M.*, Sharp, W.D., Tryon, C.A., Faith, J.T., Lewis, J., Ranhorn, K., Mambelli, S., Miller, M.J., Dawson, M.J. (2020). Carbon, nitrogen, and oxygen isotopes of ostrich eggshells provide site-scale Pleistocene-Holocene paleoenvironmental records for eastern African archaeological sites. Quaternary Science Reviews 230: 106142. DOI: 10.1016/j.quascirev.2019.106142
Williams, R.T.**, Mozley, P.S., Sharp, W.D., Goodwin, L.B. (2019). U-Th Dating of Syntectonic Calcite Veins Reveals the Dynamic Nature of Fracture Cementation and Healing in Faults. Geophysical Research Letters 46: 12900-12908. DOI: 10.1029/2019GL085403
Sharp, W.D., Tryon, C.A., Niespolo, E.M.*, Fylstra, N.D., Tripathy-Lang, Faith, J.T. (2019). 230Th/U burial dating of ostrich eggshell. Quaternary Science Reviews 219: 263-276. DOI: 10.1016/j.quascirev.2019.06.037
Sharp, Warren D., Paces, James B., (2018) Comment on "The earliest modern humans outside Africa". Science 362: (6413) Article No. eaat6598. DOI: 10.1126/science.aat6598
Oster, J.L., Sharp, W.D., Covey, A.K., Gibsen, J., Rogers, B., Mix, H. (2017). Climate response to the 8.2 ka event in coastal California. Scientific Reports 7: 3886. DOI: 10.1038/s41598-017-04215-5
Authors were students (*) or postdocs (**) when article was published