- Baylor University, Geology, Graduate StudentGeorgia State University, Geosciences, Post-Doc, and 2 moreadd
- Paleolithic Archaeology, Middle Stone Age (Archaeology), Vertebrate taphonomy, Geosciences, Paleopedology, Soil Genesis and Paleopedology, and 8 moreTravertine and Tufa formation, Limnology of tropical lakes, Soil Science, Paleoclimatology, Paleoclimate, Quaternary, Human Evolution, and Quaternary Sedimentology and Geomorphologyedit
Here we report our recent discovery of a new obsidian source in central Armenia. Using portable XRF, we were able to chemically identify Ptghni obsidian as a previously unrecognized source on the same day that we first encountered it... more
Here we report our recent discovery of a new obsidian source in central Armenia. Using portable XRF, we were able to chemically identify Ptghni obsidian as a previously unrecognized source on the same day that we first encountered it during our field surveys. Obsidian was found in alluvial-lacustrine sediments exposed within the Hrazdan Gorge, where it had been deposited after having eroded from an upstream source. These sediments were covered by mafic lavas and later exposed by downcutting of the Hrazdan River. Based on the stratigraphy of the gorge, the lava flows -- and, therefore, the sediments sandwiched between them -- predate 441 ka. The composition of Ptghni obsidian does not fit into the chemical trends of known sources in the Gegham and Tsaghkunyats ranges, so its precise volcanic origin remains unknown. Comparisons to unidentified artifacts in the literature revealed no matches, but obsidian sourcing work in Armenia has largely focused on the Holocene, when the Ptghni source might no longer have been accessible. The discovery of Ptghni obsidian is crucial for research into early hominin expansions given that it was an obsidian source available for use as toolstone by hominins during the Early and/or Middle Pleistocene.
Research Interests: Archaeology, Prehistoric Archaeology, Archaeological Science, Palaeolithic Archaeology, Obsidian, and 13 moreLithic Technology, X-Ray Fluorescence (XRF) Spectroscopy, Lithics, Archaeological Chemistry, Archaeological Fieldwork, Armenia, Provenance studies of archaeological material, portable XRF (PXRF) in Archaeology and Museum Science, South Caucasus, Lithic Raw Material Sourcing, Obsidian Sourcing, Archaeological field methods, and Geological Field Mapping
A B S T R A C T Here we report our recent discovery of a new obsidian source in central Armenia. Using portable XRF, we were able to chemically identify " Ptghni " obsidian as a previously unrecognized source on the same day that we first... more
A B S T R A C T Here we report our recent discovery of a new obsidian source in central Armenia. Using portable XRF, we were able to chemically identify " Ptghni " obsidian as a previously unrecognized source on the same day that we first encountered it during our field surveys. Obsidian was found in alluvial-lacustrine sediments exposed within the Hrazdan Gorge, where it had been deposited after having eroded from an upstream source. These sediments were covered by mafic lavas and later exposed by downcutting of the Hrazdan River. Based on the stratigraphy of the gorge, the lava flows – and, therefore, the sediments sandwiched between them – predate 441 ka. The composition of Ptghni obsidian does not fit into the chemical trends of known sources in the Gegham and Tsaghkunyats ranges, so its precise volcanic origin remains unknown. Comparisons to unidentified artifacts in the literature revealed no matches, but obsidian sourcing work in Armenia has largely focused on the Holocene, when the Ptghni source might no longer have been accessible. The discovery of Ptghni obsidian is crucial for research into early hominin expansions given that it was an obsidian source available for use as toolstone by hominins during the Early and/or Middle Pleistocene.
Olduvai Gorge, Tanzania is known for its fossil and cultural record of early hominins. The archaeological records are typically found within pedogenically modified sediments, thus the interpretation of paleosols provides important... more
Olduvai Gorge, Tanzania is known for its fossil and cultural record of early hominins. The archaeological records are typically found within pedogenically modified sediments, thus the interpretation of paleosols provides important paleoenvironmental context information. The Gorge contains a rich and diverse record of paleosols that vary spatially and temporally, however the stratigraphy can be divided into time slices using dated tuffs and studied in a paleolandscape context. Sediments were deposited in a semi-arid closed rift basin containing paleo Lake Olduvai, with volcanoes supplying volcaniclastic material to an alluvial fan system on the eastern side and quartzofeldspathic fluvial sediments derived from weathered basement rocks on the western side. The shallow saline-alkaline lake in the basin center and groundwater levels in the surrounding uplands fluctuated with Milankovitch-driven climatic (precession) cycles of w20,000 years. The rift basin paleolandscape (at w1.8 Ma) is reconstructed using sedimentology, stratigraphy and paleopedology. Standard field descriptions of physical and biogenic paleosol structures are combined with stable isotope ratios of carbonates, and whole rock geochemistry of sediments, to reveal diversity of paleosols within the basin. There are at least three distinct types of paleosols that record a paleocatena related to both landscape and drainage differences. Red tephra-rich Andisols developed on the volcaniclastic alluvial fan to the east of the paleolake, calcium-carbonate-rich, silty Aridisols developed on the interfluves and floodplain of the fluvial plain on the west, whereas clay-rich paleosols (Vertisols) developed on the lake margin and lake in the center of basin. Variances in geo-morphology, depositional environment, parent material, and depth to the water table are reflected in the development of distinctly different soil types that can provide key data needed for high-resolution reconstruction of the landscape known to be utilized by early hominins.
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Research Interests:
The provenance of the Cretaceous Hornbrook Formation, deposited unconformably on the eastern terranes of the Klamath Mountains of northern California and southern Oregon, may prove critical to reconstructing the complex Cretaceous... more
The provenance of the Cretaceous Hornbrook Formation, deposited unconformably on the eastern terranes of the Klamath Mountains of northern California and southern Oregon, may prove critical to reconstructing the complex Cretaceous paleogeography of this region. Sandstone petrography from each of the five members of the Hornbrook Formation indicates a variable source region with elements from basement uplift, transitional continent, recycled
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Open-air archaeological sites record only a small fraction of the behavioral traces of mobile forager populations. Whereas caves and rockshelters were often occupied at least in part for protection from the elements, the reasons why human... more
Open-air archaeological sites record only a small fraction of the behavioral traces of mobile forager populations. Whereas caves and rockshelters were often occupied at least in part for protection from the elements, the reasons why human foragers occupied other places on the landscape (however briefly) are varied and not always readily recoverable. We develop a framework for interpreting human use of the landscape and modeling occupation of open-air sites using the archaeological and paleoenvironmental record of Middle Stone Age (MSA) sites from Rusinga and Mfangano Islands, located near the eastern margin of Lake Victoria. Paleoenvironmental reconstructions using fossil faunas suggest an arid grassland setting unlike the present. Paleoecological modeling of the habitats of extant and extinct bovids, combined with GIS-based reconstructions of lake level change, indicate that human occupation of these sites coincided with substantial declines in the level of Lake Victoria. During this time, both Rusinga and Mfangano would have been connected to the mainland and represented local topographic highs within an extensive grassland. Geological, ecological, and ethnobotanical observations suggest that these topographic high points would likely have been important sources of stone raw material, fresh water, and a variety of plant resources for food, fuel, and other purposes. In contrast, the grassy lowland plains were probably exploited primarily as a source of large game, which included numerous species of large gregarious grazers, several of which may have followed now extinct migration routes.
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Research Interests:
Research Interests:
Research Interests:
The effect of changing environment on the evolution of Homo sapiens is heavily debated, but few data are available from equatorial Africa prior to the last glacial maximum. The Karungu deposits on the northeast coast of Lake Victoria are... more
The effect of changing environment on the evolution of Homo sapiens is heavily debated, but few data are
available from equatorial Africa prior to the last glacial maximum. The Karungu deposits on the northeast coast
of Lake Victoria are ideal for paleoenvironmental reconstructions and are best studied at the Kisaaka site near
Karunga in Kenya (94 to N33 ka) where paleosols, fluvial deposits, tufa, and volcaniclastic deposits (tuffs) are exposed
over a ~2 km transect. Three well-exposed and laterally continuous paleosols with intercalated tuffs allow
for reconstruction of a succession of paleocatenas. The oldest paleosol is a smectitic paleo-Vertisol with saline and
sodic properties. Higher in the section, the paleosols are tuffaceous paleo-Inceptisols with Alfisol-like soil characteristics
(illuviated clay). Mean annual precipitation (MAP) proxies indicate little change through time, with an
average of 764 ± 108 mm yr−1 for Vertisols (CALMAG) and 813 ± 182 to 963 ± 182 mm yr−1 for all paleosols
(CIA-K). Field observations and MAP proxies suggest that Karungu was significantly drier than today, consistent
with the associated faunal assemblage, and likely resulted in a significantly smaller Lake Victoria during the late
Pleistocene. Rainfall reduction and associated grassland expansion may have facilitated human and faunal dispersals
across equatorial East Africa.
available from equatorial Africa prior to the last glacial maximum. The Karungu deposits on the northeast coast
of Lake Victoria are ideal for paleoenvironmental reconstructions and are best studied at the Kisaaka site near
Karunga in Kenya (94 to N33 ka) where paleosols, fluvial deposits, tufa, and volcaniclastic deposits (tuffs) are exposed
over a ~2 km transect. Three well-exposed and laterally continuous paleosols with intercalated tuffs allow
for reconstruction of a succession of paleocatenas. The oldest paleosol is a smectitic paleo-Vertisol with saline and
sodic properties. Higher in the section, the paleosols are tuffaceous paleo-Inceptisols with Alfisol-like soil characteristics
(illuviated clay). Mean annual precipitation (MAP) proxies indicate little change through time, with an
average of 764 ± 108 mm yr−1 for Vertisols (CALMAG) and 813 ± 182 to 963 ± 182 mm yr−1 for all paleosols
(CIA-K). Field observations and MAP proxies suggest that Karungu was significantly drier than today, consistent
with the associated faunal assemblage, and likely resulted in a significantly smaller Lake Victoria during the late
Pleistocene. Rainfall reduction and associated grassland expansion may have facilitated human and faunal dispersals
across equatorial East Africa.
Research Interests:
The effect of changing palaeoclimate and palaeoenvironment on human evolution during the Pleistocene is debated, but hampered by few East African records directly associated with archaeological sites prior to the Last Glacial Maximum.... more
The effect of changing palaeoclimate and palaeoenvironment on human evolution during the
Pleistocene is debated, but hampered by few East African records directly associated with
archaeological sites prior to the Last Glacial Maximum. Middle to Late Pleistocene deposits on
the shoreline of eastern Lake Victoria preserve abundant vertebrate fossils and Middle Stone Age
artefacts associated with riverine tufas at the base of the deposits, which are ideal for palaeoenvironmental reconstructions. New data from tufas identified on Rusinga Island and on
the mainland near Karungu, Kenya are provided from outcrop, thin-sections, mineralogical,
stable isotopic and U-series dating analyses. Tufa is identified at four sites: Nyamita (94.0 ± 3.3
and 111.4 ± 4.2 ka); Kisaaka, Aringo (455 ± 45 ka); and Obware. The age ranges of these tufa
deposits demonstrate that spring-fed rivers were a recurrent, variably preserved feature on the
Pleistocene landscape for ca 360 kyr. Poor sorting of clastic facies from all sites indicates flashy,
ephemeral discharge, but these facies are commonly associated with barrage tufas, paludal
environments with δ13C values of ca 10‰ indicative of C3 plants and fossil Hippopotamus, all of
which indicate a perennial water source. Other tufa deposits from Nyamita, Obware and Aringo
have a mixed C3/C4 signature consistent with a semi-arid C4 grassland surrounding these springfed
rivers. The δ18O values of tufa from Nyamita are on average ca 1‰ more negative than
calcite precipitated from modern rainfall in the region, suggesting greater contribution of
depleted monsoonal input, similar to the Last Glacial Maximum. Microdebitage and surface
collected artefacts indicate that early modern humans were utilizing these spring-fed rivers. The
presence of spring-fed rivers would have afforded animals a reliable water source, sustaining a
diverse plant and animal community in an otherwise arid environment.
Pleistocene is debated, but hampered by few East African records directly associated with
archaeological sites prior to the Last Glacial Maximum. Middle to Late Pleistocene deposits on
the shoreline of eastern Lake Victoria preserve abundant vertebrate fossils and Middle Stone Age
artefacts associated with riverine tufas at the base of the deposits, which are ideal for palaeoenvironmental reconstructions. New data from tufas identified on Rusinga Island and on
the mainland near Karungu, Kenya are provided from outcrop, thin-sections, mineralogical,
stable isotopic and U-series dating analyses. Tufa is identified at four sites: Nyamita (94.0 ± 3.3
and 111.4 ± 4.2 ka); Kisaaka, Aringo (455 ± 45 ka); and Obware. The age ranges of these tufa
deposits demonstrate that spring-fed rivers were a recurrent, variably preserved feature on the
Pleistocene landscape for ca 360 kyr. Poor sorting of clastic facies from all sites indicates flashy,
ephemeral discharge, but these facies are commonly associated with barrage tufas, paludal
environments with δ13C values of ca 10‰ indicative of C3 plants and fossil Hippopotamus, all of
which indicate a perennial water source. Other tufa deposits from Nyamita, Obware and Aringo
have a mixed C3/C4 signature consistent with a semi-arid C4 grassland surrounding these springfed
rivers. The δ18O values of tufa from Nyamita are on average ca 1‰ more negative than
calcite precipitated from modern rainfall in the region, suggesting greater contribution of
depleted monsoonal input, similar to the Last Glacial Maximum. Microdebitage and surface
collected artefacts indicate that early modern humans were utilizing these spring-fed rivers. The
presence of spring-fed rivers would have afforded animals a reliable water source, sustaining a
diverse plant and animal community in an otherwise arid environment.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a... more
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that ...