I am a palynologist (pollen and spores) with expertise in paleoecology, paleoclimatology, and biostratigraphy. My biostratigraphic expertise extends from the Carboniferous to the Holocene, with an emphasis on Euramerica (Paleozoic) and the Northern Hemisphere. My paleoclimate expertise includes the late Paleozoic and the Paleogene to Holocene intervals.
Editorial Boards
- Global and Planetary Change
- Frontiers in Ecology and Evolution – Paleoecology section Review Editor
- Quaternary
- Review of Palaeobotany and Palynology
Professional Experience
2021-Present Research Geologist, US Geological Survey, Reston, Virginia
2011-2021 Coordinator, USGS Climate Research & Development Program
1991-2011 Research Geologist, US Geological Survey, Reston, Virginia
1990-1991 Postdoctoral Researcher, National Museum of Natural History, Smithsonian Institution, Washington, DC
Education and Certifications
University of Illinois at Urbana-Champaign - Ph.D., Botany 1990
University of Illinois at Urbana-Champaign - M.S., Botany 1985
The Pennsylvania State University - B.S., Botany 1982
Stephens College - A.A., Geology 1980
Affiliations and Memberships
American Geophysical Union
Geological Society of America
The Palynological Society
Science and Products
Filter Total Items: 101
Effects of climate variability and human activities on Chesapeake Bay and the implications for ecosystem restoration
Chesapeake Bay, the Nation’s largest and most productive estuary (fig. 1), faces complex environmental issues related to nutrients and oxygen, turbidity and sedimentation, toxic dinoflagellates, sea-level rise, and coastal erosion. The Chesapeake Bay Program (CBP) is a partnership among the Chesapeake Bay Commission, the Federal Government, the District of Columbia, and the States of Maryland, Vir
Neogene and Quaternary geology of a stratigraphic test hole on Horn Island, Mississippi Sound
During April and May, 1991, the U.S. Geological Survey (USGS) drilled a 510-ft-deep, continuously cored, stratigraphic test hole on Horn Island, Mississippi Sound, as part of a field study of the Neogene and Quaternary geology of the Mississippi coastal area. The USGS drilled two new holes at the Horn Island site. The first hole was continuously cored to a depth of 510 ft; coring stopped at this d
PRISM 8 degrees X 10 degrees North Hemisphere paleoclimate reconstruction; digital data
The PRISM 8?x10? data set represents several years of investigation by PRISM (Pliocene Research, Interpretation, and Synoptic Mapping) Project members. One of the goals of PRISM is to produce time-slice reconstructions of intervals of warmer than modern climate within the Pliocene Epoch. The first of these was chosen to be at 3.0 Ma (time scale of Berggren et al., 1985) and is published in Global
Arctic vegetation, temperature, and hydrology during Early Eocene transient global warming events
Early Eocene global climate was warmer than much of the Cenozoic and was punctuated by a series of transient warming events or ‘hyperthermals’ associated with carbon isotope excursions when temperature increased by 4–8° C. The Paleocene-Eocene Thermal Maximum (PETM, ~55 Ma) and Eocene Thermal Maximum 2 (ETM2, 53.5 Ma) hyperthermals were of short duration (< 200 kyr) and dramatically restructured t
Climatic variability in the eastern United States over the past millennium from Chesapeake Bay sediments
Salinity oscillations caused by multidecadal climatic variability had major impacts on the Chesapeake Bay estuarine ecosystem during the past 1000 yr. Microfossils from sediments dated by radiometry (14C, 137Cs, 210Pb) and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10-15 ppt during periods of extreme drought (low fresh-water discharge) and wet climate (high dischar
Rapid inundation of the southern Florida coastline despite low relative sea-level rise rates during the late-Holocene
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR ra
By
Natural Hazards, Ecosystems, Coastal and Marine Hazards and Resources Program, Land Change Science Program, Climate Adaptation Science Centers, Climate Research and Development Program, Climate Adaptation Science Center, Florence Bascom Geoscience Center, St. Petersburg Coastal and Marine Science Center
Chronology from sediment cores collected in southwestern Everglades National Park, Florida
Age model data are presented for 10 cores from the southwestern coastal mangrove zone of Everglades National Park, Florida, collected in Common Era (CE) 2004 and 2005 and used for paleoecological analysis. Carbon-14 (14C), lead-210 (210Pb), cesium-137 (137Cs), radium-226 (226Ra), and pollen biostratigraphic information is included, and age models were generated for 6 of the 10 cores. Age reversals
The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean
A new 2400-year paleoclimate reconstruction from Chesapeake Bay (CB) (eastern US) was compared to other paleoclimate records in the North Atlantic region to evaluate climate variability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Using Mg/Ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation-driven estuarine hyd
Response of the everglades ridge and slough landscape to climate variability and 20th-century water management
The ridge and slough landscape of the Florida Everglades consists of a mosaic of linear sawgrass ridges separated by deeper-water sloughs with tree islands interspersed throughout the landscape. We used pollen assemblages from transects of sediment cores spanning sawgrass ridges, sloughs, and ridge-slough transition zones to determine the timing of ridge and slough formation and to evaluate the re
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Filter Total Items: 101
Effects of climate variability and human activities on Chesapeake Bay and the implications for ecosystem restoration
Chesapeake Bay, the Nation’s largest and most productive estuary (fig. 1), faces complex environmental issues related to nutrients and oxygen, turbidity and sedimentation, toxic dinoflagellates, sea-level rise, and coastal erosion. The Chesapeake Bay Program (CBP) is a partnership among the Chesapeake Bay Commission, the Federal Government, the District of Columbia, and the States of Maryland, VirNeogene and Quaternary geology of a stratigraphic test hole on Horn Island, Mississippi Sound
During April and May, 1991, the U.S. Geological Survey (USGS) drilled a 510-ft-deep, continuously cored, stratigraphic test hole on Horn Island, Mississippi Sound, as part of a field study of the Neogene and Quaternary geology of the Mississippi coastal area. The USGS drilled two new holes at the Horn Island site. The first hole was continuously cored to a depth of 510 ft; coring stopped at this dPRISM 8 degrees X 10 degrees North Hemisphere paleoclimate reconstruction; digital data
The PRISM 8?x10? data set represents several years of investigation by PRISM (Pliocene Research, Interpretation, and Synoptic Mapping) Project members. One of the goals of PRISM is to produce time-slice reconstructions of intervals of warmer than modern climate within the Pliocene Epoch. The first of these was chosen to be at 3.0 Ma (time scale of Berggren et al., 1985) and is published in GlobalArctic vegetation, temperature, and hydrology during Early Eocene transient global warming events
Early Eocene global climate was warmer than much of the Cenozoic and was punctuated by a series of transient warming events or ‘hyperthermals’ associated with carbon isotope excursions when temperature increased by 4–8° C. The Paleocene-Eocene Thermal Maximum (PETM, ~55 Ma) and Eocene Thermal Maximum 2 (ETM2, 53.5 Ma) hyperthermals were of short duration (< 200 kyr) and dramatically restructured tClimatic variability in the eastern United States over the past millennium from Chesapeake Bay sediments
Salinity oscillations caused by multidecadal climatic variability had major impacts on the Chesapeake Bay estuarine ecosystem during the past 1000 yr. Microfossils from sediments dated by radiometry (14C, 137Cs, 210Pb) and pollen stratigraphy indicate that salinity in mesohaline regions oscillated 10-15 ppt during periods of extreme drought (low fresh-water discharge) and wet climate (high discharRapid inundation of the southern Florida coastline despite low relative sea-level rise rates during the late-Holocene
Sediment cores from Florida Bay, Everglades National Park were examined to determine ecosystem response to relative sea-level rise (RSLR) over the Holocene. High-resolution multiproxy analysis from four sites show freshwater wetlands transitioned to mangrove environments 4–3.6 ka, followed by estuarine environments 3.4–2.8 ka, during a period of enhanced climate variability. We calculate a RSLR raByNatural Hazards, Ecosystems, Coastal and Marine Hazards and Resources Program, Land Change Science Program, Climate Adaptation Science Centers, Climate Research and Development Program, Climate Adaptation Science Center, Florence Bascom Geoscience Center, St. Petersburg Coastal and Marine Science CenterChronology from sediment cores collected in southwestern Everglades National Park, Florida
Age model data are presented for 10 cores from the southwestern coastal mangrove zone of Everglades National Park, Florida, collected in Common Era (CE) 2004 and 2005 and used for paleoecological analysis. Carbon-14 (14C), lead-210 (210Pb), cesium-137 (137Cs), radium-226 (226Ra), and pollen biostratigraphic information is included, and age models were generated for 6 of the 10 cores. Age reversalsThe Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean
A new 2400-year paleoclimate reconstruction from Chesapeake Bay (CB) (eastern US) was compared to other paleoclimate records in the North Atlantic region to evaluate climate variability during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Using Mg/Ca ratios from ostracodes and oxygen isotopes from benthic foraminifera as proxies for temperature and precipitation-driven estuarine hydResponse of the everglades ridge and slough landscape to climate variability and 20th-century water management
The ridge and slough landscape of the Florida Everglades consists of a mosaic of linear sawgrass ridges separated by deeper-water sloughs with tree islands interspersed throughout the landscape. We used pollen assemblages from transects of sediment cores spanning sawgrass ridges, sloughs, and ridge-slough transition zones to determine the timing of ridge and slough formation and to evaluate the re - News