Sedimentary Geology & Paleontology
Sediments, sedimentary rocks, and their fossil contents provide a record of how the Earth's surficial processes have evolved over the past ~4 billion years. As such, the sedimentary record provides a means for us to explore how the Earth has worked at times when atmospheric CO2, oceanic oxygen, marine/terrestrial organisms, and tectonic configurations were quite different from what is observed today. Utilizing an integrated field, petrographic, isotope-geochemical, and geochronological approach, faculty and students at UNLV conduct research projects on the sedimentological, biological, and geochemical responses to paleoclimate changes, ocean circulation changes, and sedimentary basin evolution.
Brenda J. Buck: Professor
Soil Science & Geomorphology of Desert Landscapes (Modern & Ancient)
Andrew D. Hanson: Associate Professor
Sedimentology, Basin Analysis, Petroleum Geology and Organic Geochemistry
Ganqing Jiang: Associate Professor
Sequence and Chemostratigraphy, Sedimentology, Carbonate Diagensis
Stephen M. Rowland: Professor
Paleontology, History of Geology
Integrating field-based sedimentological investigations and new techniques such as stable isotopes, SEM and Ion Probe, XRD-XRF analyses, and Ar-Ar age dating, faculty and students at UNLV explore the sedimentological responses to changes in paleoclimate, ocean circulation patterns, and tectonic activities of sedimentary basins. Existing projects include: (1) control of carbonate depositional cycles under supergreenhouse times when high pCO2 potentially prevented the development of polar ice sheets (Mesoproterozoic, Cambrian, and Cretaceous); (2) temporal and spatial facies variations associated with the initiation, filling, and termination of synrift basins, particularly in the Paleozoic passive continental margin of the western US (the Great Basin); (3) development and preservation of microbially induced sedimentary structures (MISS) under highly stressed depositional environments; (4) diagenetic patterns, porosity changes, and petroleum reservoir evaluation of major unconformities in Paleozoic carbonate platforms.
Our students and faculty study stratigraphic relationships in a variety of settings, including modern lake settings, ancient passive margins, and extensional basins. Methods employed range from core collection and analysis in modern settings to carbon and oxygen isotope chemostratigraphic studies of ancient systems. Completed and ongoing projects include: stratigraphic evolution of the Las Vegas Wash Bay and Lake Mead; the relationship between sea-level changes and carbon isotope anomalies; and potential surface- to deep-water carbon isotope gradient in Neoproterozoic and Paleozoic sedimentary basins.
We study sedimentary basins in a variety of settings in order to understand how tectonic evolution impacts basin development and preservation. Tools employed in these studies include geologic mapping, facies interpretation, paleocurrent analysis, sedimentary petrography, molecular organic geochemistry, basin modeling, detrital zircon analyses, apatite-fission track analysis, U/Th-He analysis, Ar/Ar geochronology, tephrochronology, and architectural element analysis. Current projects include: linked stratigraphic and structural analysis of the Frenchman Mountain fault; provenance, stratigraphic and structural evolution of the Miocene Muddy Creek Formation near Mesquite, NV; and synconvergent latest Cretaceous to Eocene extensional basins in the Sevier hinterland. Completed projects include: tectonic evolution of the Altyn Tagh fault along the northern margin of the Tibetan Plateau; age and setting of the Bikou terrane in central China; basin analysis of the central Grand Wash Trough in AZ and NV; and depositional history of the Black Mountain Conglomerate in northwest AZ.
So far, work in petroleum geology has focused on maturation, generation, and migration of hydrocarbons in basins impacted by salt tectonics. Tools employed in these research projects include basin modeling, thermal assessment using vitrintie reflectance and fluid inclusion data, and molecular organic geochemistry. Current projects include: hydrocarbon migration along a sub-vertical weld; and assessing the thermal anomaly around a subaerial diapir (both projects are based in La Popa basin, northeastern Mexico). Completed projects include oil and source rock geochemistry studies of the Ordos Basin, north central China and the Talara basin, Peru. New projects are aimed at assessing resource potential in Railroad Valley, NV, a Tertiary extensional basin.
Faculty and students are actively engaged in paleoecological studies of Pleistocene mammalian faunas, and the paleoecology of Cambrian and Neoproterozoic reef ecosystems. Projects include: the climate and environmental control on the phylogenetic evolution and extinction of Cambrian Archaeocyaths; the climate and environmental control on the disappearance of reef systems from middle Cambrian to Middle Ordovician; and paleoecology of Pleistocene mammoths in response to paleoclimate and vegetation changes.
One of the most intriguing questions in Earth Sciences is what was on land before the fossil record of land plants in Silurian (and possibly late Cambrian to Ordovician). Information on pre-Silurian paleosols is still sparse, and their biological and geochemical contents are uncertain. In this case, identification of pre-Silurian paleosols is critical. At UNLV, faculty and students attempt to identify paleosols from Cambrian (western US) and Mesoproterozoic (north China) successions through a detailed sedimentological and petrographic perspective, and compare their geochemical contents with post-Silurian paleosols to explore paleoclimate changes.
Changes in ocean redox conditions are considered crucial to biospheric evolution in Earth history. One of the most intriguing time periods is the late Neoproterozoic to early Cambrian that witnessed the first appearance and explosion of animals. Another intriguing time period is the Middle-Late Cretaceous during which the global ocean was transitioned from prominently anoxic to oxic (as recorded by high-TOC shales and widespread oceanic red beds, respectively). With collaborators from other institutions in the US and China, our faculty and students study the redox evolution associated with the early animal evolution in the Ediacaran-Cambrian succession, and the marine and terrestrial Cretaceous successions in China.