Research

Engare Sero Footprint Project

Since 2008, I've been the Scientific Director of the the Engare Sero Footprint Project. Our research group studies early human footprints pressed into a debris flow made of volcanic ash and sediment on the southern shore of Lake Natron, in the shadow of the active volcano Oldoinyo L'engai. Our goal is to reconstruct the landscape of this area ~10,000-19,000 years ago when a group of ancient Homo sapiens trudged through the wet lake margin. This research is a collaborative effort between geologists and paleoanthropologists in the US and Tanzania, from Appalachian State University, the Smithsonian Institute, the George Washington University, Rutgers University, and the American Museum of Natural History, with funding from National Geographic and the Leakey Foundation. Our results are published in Palaeo³, Sept 2016. For more information, please see the recent articles by National Geographic, the Washington Post, and even the High Country Press.

Other media articles on the Engare Sero research can be found here.

*Update: new research (Aug 2018) on the erosion of the Engare Sero footprints using 3D structure-from-motion analyses, highlighted here.

Loperot Miocene Project

I am a Co-PI of the Loperot Miocene Project, in collaboration with researchers from Midwestern University (Dr. Aryeh Grossman) and Mercer University (Dr. Francis Kirera). We aim to reconstruct the paleoecology of a west Turkana fossil-bearing site (Loperot) during the Early Miocene in order to assess the variety of environments that various primates inhabited. With funding from the Leakey Foundation, our initial results indicate a unique faunal assemblage at Loperot (including a few new species!), and that the landscape was a riparian, gallery forest rather than a closed-canopy, humid forest that is proposed for other Early Miocene ape sites. Our results are published in the International Journal of Primatology (2014) with 2 more papers ready to be submitted any day now (Spring 2018).

Walvis Bay, Namibia Footprints

In collaboration with Dr. Francis Thackeray (University of Witswatersrand) and Dr. Matthew Bennett (Bournemouth University), along with the critical assistance of Fanie DuPreez (Kuiseb Delta Adventures), I study Holocene human and animal footprints in the Namib Desert just east of Walvis Bay, Namibia. Several sites between the desert dunes contain footprints of humans and various animals, including one site containing a trackway of an adult elephant and another comprised only of footprints of children. While these prints are only ~2000 years old, they represent an amazing assemblage of human and animal trackways that record life in Namibia during times when the Kuiseb River flooded. Our results are published in the International Journal of Physical Anthropology and the Journal of African Earth Science.

Proterozoic Konnarock Formation

Thanks to the interest and initiative of undergraduate research student Griffin Moyer (App State '16), we are analyzing outcrops of the Neoproterozoic Konnarock Formation in southwestern Virginia. Through field mapping and thin section analysis of the rhythmites found in the lower Konnarock Fm, we identified various subfacies and developed a model to explain the distribution of each characteristic facies within the formation. Micromorphologic features within the sediments show that paleoLake Konnarock changed from an ice distal to an ice proximal paleolake. For further information, please see our recent GSA abstract.

Solite Quarry, VA (Triassic rift basin)

The fossiliferous Triassic sediments exposed in the Virginia Solite Quarry (part of the Danville-Dan River rift basin) include a 34-mm-thick "insect layer" that is notable for preserving exquisite details, including soft-bodied invertebrates (above) as well as vertebrate remains. This research project describes this unique Lagerstatte and uses sedimentologic and geochemical analyses to interpret the depositional environment as well as the preservation conditions that created this amazing assemblage. Our analyses illustrate that long-accepted models of rift basin sedimentology may not be applicable across the entire Newark Supergroup. Specifically, we show that dark laminated mudstones do not, in fact, indicate deep, anoxic, lacustrine environments, but instead indicate a shallow, oxygenated, yet toxic lake margin. The absence of bioturbation by plants and benthic organisms as well as the lack of predation on the insects (thus aiding their preservation) is not explained, therefore, by significant water depth, but instead more reasonably considered a result of the chemistry of the water at the lake margin, affected by groundwater seeps, which provide F-, Mg-, and Ca-rich fluids. Our results are presented in a paper in the Journal of Paleolimnology and the insects are described in detail in a new publication by Dunedin Press, Terrestrial Conservation Lagerstatte (coming in Fall 2017).

"Phytocretions"

"Phytocretions" are calcite plant encrustations that form in standing water above the sediment surface (similar to tufa or "spring chalk") but mimic rhizoliths in their outward morphology. It is important to recognize this type of carbonate in the fossil record. If confused with rhizoliths, they may be interpreted as soil carbonates. Instead, they form above the sediment surface in standing water during a very short period of time (the growing season of the plant). Rather than recording dry conditions (as pedogenic carbonates often do), they record ambient aquatic conditions at the time of their precipitation (PDF here). I have reported several instances where these "phytocretions" can record important details of lake-margin groundwater hydrology and climate change, including Pleistocene sediments at Olduvai Gorge and modern systems in Pilot Valley, NV. My research indicates that phytocretions can form very quickly under the best conditions, and can therefore record changes in ambient water conditions on the scale of months. Thus, stable isotope values of microsamples within single phytocretions may be suitable for interpreting short term climate change (on the order of months to years) but to infer longer scale climate change (decadal scale or longer) one must analyze the isotopic composition of populations of phytocretions.