Welcome to Lindsay J. McHenry's web page!
Dr. Lindsay J. McHenry
Mineralogy, volcanology, geoarchaeology, Mars geology
Department of Geosciences
University of Wisconsin-Milwaukee
P.O. Box 413
Office: Lapham Hall 324
Lab: Lapham Hall 377
Phone: (414) 229-3951
Office hours: MW 10-10:50
Lindsay McHenry (and Papa) on the rim of Olmoti volcanic crater,
Spring 2011: Planetary Geology
Fall 2010: Principles of Mineralogy
Spring 2010: X-Ray Analytical Methods
Spring 2010: Introductory Physical Geology
Spring 2009: Geochronology
I use the composition of volcanic ash to correlate between archaeological sites in East Africa. Individual volcanic eruptions produce and deposit volcanic ash layers of distinct compositions that can often be uniquely identified over broad areas. Where these ashes are preserved between stratigraphic layers of archaeological interest, we can create stratigraphic frameworks for important evolutionary and cultural changes throughout a region.
I have applied this technique to the Plio-Pleistocene volcanic ashes of Bed I, the oldest and thickest bed at Olduvai Gorge, Tanzania. Specimens of Homo habilis and Paranthropus boisei, along with abundant stone tools, faunal remains, and cut-marked bones, have been found at sites throughout the Olduvai basin. These specimens are found between the layers of volcanic ash produced by the nearby Ngorongoro Volcanic Highlands.
Unfortunately, the volcanic ash layers are poorly preserved because of the saline-alkaline lake and groundwater conditions at the time of (and since) deposition. At most sites the volcanic glass, the phase most often used for "fingerprinting" volcanic ashes, is altered to clay and zeolite and unusable. I have instead focused on the phenocrysts (volcanic minerals) for characterization and correlation. Using phenocryst composition, I have uniquely identified and correlated the major Bed I volcanic ashes throughout the basin, creating a high-resolution stratigraphic framework for Bed I. This framework has been used to place the new finds (including a Homo habilis maxilla) from the lesser-known western part of Olduvai into context with the better-known eastern sites.
I am currently working to expand both the regional and temporal scope of this project. I have collected volcanic ash samples from Laetoli, an older (Late Pliocene) archaeological site to the southwest of Olduvai, from the younger Beds (Bed II and up) at Olduvai, from Peninj (to the north of Olduvai), and the Manyara Beds (to the east). My goal is to establish a regional stratigraphic framework based on volcanic ash compositions for Plio-Pleistocene (and Holocene) Tanzania that can be used for regional correlation between sites of paleoanthropological, paleoclimatological, and paleoecological interest.
Other interests include the study of volcanic ash alteration processes, establishing a regional record of explosive volcanism for Tanzania, and correlating volcanic ash layers between terrestrial and marine environments. In addition to work in Tanzania I have also participated in a 2005 research cruise off the coast of New Zealand. Using core samples collected during that cruise I intend to study the compositional changes in volcanic ash deposited in a marine environment.
I have recently started looking at the alteration of volcanic materials (lava and ash) in a number of different diagenetic environments as a potential analogue for the Mars surface materials analyzed by the Mars rovers Opportunity and Spirit. So far this project involves saline-alkaline alteration of volcanic ash at Olduvai, and basalt alteration and sulfate precipitation in lava tubes at Craters of the Moon National Monument, Idaho. Check my publications page for recent abstracts and conference proceedings papers, and stay tuned for updates!
For a nice, brief summary of my research interests, please check out this recent article from the UWM home page on my work.
A postcard from Olduvai Gorge, Tanzania, featuring a reconstruction of the Zinjanthropus (A. boisei) skull.
The Olduvai Landscape Palaeoanthropology Project (OLAPP) group at the Zinjanthropus discovery site, Olduvai Gorge, Tanzania. The lighter layers in the outcrop are volcanic ash layers.
Electron backscatter image of volcanic glass shards and mineral grains from a fresh volcanic ash layer, 250X magnification.
Lindsay McHenry lounging aboard the RV-Revelle research vessel off the coast of New Zealand, March 2005.