Biogeosciences: Paleoclimatology, and Geoarchaeology
Lithospheric Processes: Geochronology
Paleoclimate: Fluvial Geomorphology, Geochronology, Human-environment interactions, Pedology and paleopedology, Quantitative geomorphology/Quaternary Environments, Geoarchaeology, Stratigraphy and Sedimentology
Hydrological and Surface Processes: Hydrology-Fluvial Geomorphology, Geochronology, Pedology and Paleopedology, Quantitative geomorphology/Quaternary environments
Faculty specific research areas: Paleoclimatology, quantitative geomorphology, Quaternary environments, geochronology, paleoseismology, Earth System Science
The research interests of our QuatPals (Quaternary Paleoclimatology) research group are centered on gaining new understanding of the progression and mechanisms of environmental and climate change in the past 2 million years of Earth's history. Investigations are often collaborative, bridging multiple disciplines, and combine field interpretations and analytical measurements, with geophysical modeling. This approach underscores the importance of translating site-specific geomorphic or stratigraphic observations or measurements to regional and global contexts on various time scales. We see an endless horizon of exciting and significance science, much, if not all collaborative with students and colleagues from many continents. Outlined below are recent and future research directions. Also, I am open to explore new research directions with post-doctoral scholars and graduate students. I enjoy mentoring excellent students to be amazing professionals and take new research pathways. The frontiers are endless.
Paleorecords and paleoclimatology of Drought: Understanding the geologic record of droughts is important for evaluating recent climate change in the context of natural variability. Extensive deposits of wind-deposited sand and silt (loess) cover much of the conterminous U.S. and indicate substantial moisture variability during glacial and interglacial periods. Research has focused on defining stratigraphic sequences, securing reliable chronologies and understanding landscape-vegetation-climate feedbacks for aridity and subsequent recovery. This research has expanded to include field studies on the Pampas of Argentina, which is “the Great Plains" of South America and climatically linked by Atlantic Ocean sea surface temperatures. We are now asking questions to assess cross-hemispheric climate linkages for the 1930’s dust bowl drought and other dry periods in the past 5000 years.
Anthropogenic impact on Earth surface processes and hydrology: Recent research underscores that human activity has significant and yet-to-be quantified impacts on surface processes and hydrology. We are accessing near surface fluvial and eolian stratigraphic records that span the past few centuries and millennia which reflect changes in vegetation cover, drainage density and landscape degradation. We are investigating the complex linkages between changes in climate, land utilization, groundwater level, and land degradation on sustainability of human-altered ecosystems.
African rift lakes and monsoon variability: A truly exciting research direction is the study of water level variability for Lake Turkana, Kenya in the past 150,000 years. The heart of research is a detailed sedimentologic, stratigraphic, and pedologic assessment coupled with high resolution dating by AMS 14C of ultra-small weight shells and novel application of luminescence dating for relict littoral and sublittoral deposits that ring the lake. This research documents multiple, centennial-scale 30+ meters swings in lake level between 15,000 and 3000 years ago reflecting state changes in the East and West African monsoons.
Andean to Atacama climate variability, southern Peru and northern Chile: A chance discovery in the northern Atacama Desert revealed a new 10’s m-thick record of eolian sand with multiple well-developed paleosols in southern coastal Peru. We hypothesis that this sequence reflects the alternating effect of two climate-sensitive moisture sources; eolian sourced from massive alluvial fans, feed from meltwater from glaciations of the Andes and the development of buried soils in response to greatly increased moisture flux from the Equatorial Pacific Ocean. The source of this moisture is unresolved but there are two likely sources, increased fog due to a persistent atmospheric inversion associated with Southeast Pacific Anticyclone or El Niño-like conditions or some combination of these sources. These important paleoclimatic records have been overlooked because of the remoteness of the field area and until recently chronologic control was elusive, but recent advances in luminescence dating of quartz are now providing credible ages.
Geochronologic Research: The accurate measuring of geologic time is a critical component in the earth sciences. A long-standing research focus is the development and application of luminescence geochronology to decipher the timing of late Quaternary (past 250 ka) climatic and environmental events, such as paleoearthquakes, volcanic eruptions, floods, lake level oscillations, fluvial degradation and aggradation, eolian deposition, burial of paleosurfaces, droughts and periods of human habitation. Analytical approaches employed include recent advances in optically stimulated luminescence using small aliquots of quartz and single grain dating. Recent research is tapping deeper trapped electrons in quartz and feldspar using the thermally-transferred signal which extend dating possibilities to 1 to 2 million years. The research horizons from the vantage point of luminescence physics is broad and deep, with recent collaborations on understanding the source of charge with triboluminescnce and electron storage potential for synthetic silica nano-compounds for solar cells.