Jeffrey S Pigati
Datos Biográficos
| ID | 3074469 |
|---|---|
| NOMBRE | Jeffrey S Pigati |
| NOMBRES | Jeffrey S |
| APELLIDO | Pigati |
| FIRMA | PIGATI J S |
| AFILIACIONES | United States Geological Survey |
| ORCID | 0000-0001-5843-6219 |
| VERIFICADO | Sí |
| TOTAL DE OBRAS | 25 |
| TOTAL DE CITAS | 54 |
| TOTAL COMO AUTOR | 25 |
| TOTAL COMO EDITOR | 0 |
| PRIMER AÑO DE PUBLICACIÓN | 2002 |
| AÑO MÁS RECIENTE DE PUBLICACIÓN | 2024 |
| ÍNDICE H | 4 |
Late glacial–Younger Dryas climate in interior Alaska as inferred from the isotope values of land snail shells
The isotope values of fossil snail shells can be important archives of climate. Here, we present the first carbon (δ 13 C) and oxygen (δ 18 O) isotope values of snail shells in interior Alaska to explore changes in vegetation and humidity through the late-glacial period. Snail shell δ 13 C values were relatively consistent through the late glacial. However, late-glacial shell δ 13 C values are 2.8‰ higher than those of modern shells. This offset …
The Geochronology of White Sands Locality 2 is Resolved
Rhode et al. [2024. “Unresolved: Persistent problems with the White Sands Locality 2 Geochronology.” PaleoAmerica] contend there are many “unresolved issues” with the geochronology of White Sands National Park (WHSA) Locality 2. They suggest there are substantial age offsets due to hard-water effects in the aquatic plants that were dated and that radiocarbon ages of pollen may be anomalously old due to reworking. In their view, the luminescence a…
Reply to “Evidence for Humans at White Sands National Park during the Last Glacial Maximum Could Actually be for Clovis People ∼13,000 Years Ago” by C. Vance Haynes, Jr
Bennett et al. (2021, Science 373, 1528–1531) reported that ancient human footprints discovered in White Sands National Park, New Mexico date to between ∼23,000 and 21,000 years ago. Haynes (2022, PaleoAmerica, this issue) proposes two alternate hypotheses to explain the antiquity of the footprints. One is that they were made by humans crossing over older sediments sometime during the Holocene. This is incorrect as there are Pleistocene megafauna…
Aeolian sediments in paleowetland deposits of the Las Vegas Formation
The Las Vegas Formation (LVF) is a well-characterized sequence of groundwater discharge (GWD) deposits exposed in and around the Las Vegas Valley in southern Nevada. Nearly monolithologic bedrock surrounds the valley, which provides an excellent opportunity to test the hypothesis that GWD deposits include an aeolian component. Mineralogical data indicate that the LVF sediments are dominated by carbonate minerals, similar to the local bedrock, but…
Oxygen isotopes in terrestrial gastropod shells track Quaternary climate change in the American Southwest
Recent studies have shown the oxygen isotopic composition (δ 18 O) of modern terrestrial gastropod shells is determined largely by the δ 18 O of precipitation. This implies that fossil shells could be used to reconstruct the δ 18 O of paleo-precipitation as long as the isotopic system, including the hydrologic pathways of the local watershed and the gastropod systematics, is well understood. In this study, we measured the δ 18 O values of 456 ind…
Evidence of humans in North America during the Last Glacial Maximum
Early footsteps in the Americas Despite a plethora of archaeological research over the past century, the timing of human migration into the Americas is still far from resolved. In a study of exposed outcrops of Lake Otero in White Sands National Park in New Mexico, Bennett et al . reveal numerous human footprints dating to about 23,000 to 21,000 years ago. These finds indicate the presence of humans in North America for approximately two millenni…
Overview of the oxygen isotope systematics of land snails from North America
Continental paleoclimate proxies with near-global coverage are rare. Land snail δ 18 O is one of the few proxies abundant in Quaternary sediments ranging from the tropics to the high Arctic tundra. However, its application in paleoclimatology remains difficult, attributable in part to limitations in published calibration studies. Here we present shell δ 18 O of modern small ( 18 O at a coarse scale. This transect is augmented by published δ 18 O …
Desert wetlands record hydrologic variability within the Younger Dryas chronozone, Mojave Desert, USA
One of the enduring questions in the field of paleohydrology is how quickly desert wetland ecosystems responded to past episodes of abrupt climate change. Recent investigations in the Las Vegas Valley of southern Nevada have revealed that wetlands expanded and contracted on millennial and sub-millennial timescales in response to changes in climate during the late Quaternary. Here, we evaluate geologic evidence from multiple localities in the Moja…
Origin of last-glacial loess in the western Yukon-Tanana Upland, central Alaska, USA
Loess is widespread over Alaska, and its accumulation has traditionally been associated with glacial periods. Surprisingly, loess deposits securely dated to the last glacial period are rare in Alaska, and paleowind reconstructions for this time period are limited to inferences from dune orientations. We report a rare occurrence of loess deposits dating to the last glacial period, ~19 ka to ~12 ka, in the Yukon-Tanana Upland. Loess in this area is…
Activation of a small ephemeral lake in southern Jordan during the last full glacial period and its paleoclimatic implications
Playas, or ephemeral lakes, are one of the most common depositional environments in arid and semiarid lands worldwide. Playa deposits, however, have mostly been avoided as paleoclimatic archives because they typically contain exceptionally low concentrations of organic material, making 14 C dating difficult. Here, we describe a technique for concentrating organic matter in sediments for radiocarbon dating and apply it to playa sediments recovered…
On the importance of stratigraphic control for vertebrate fossil sites in Channel Islands National Park, California, USA
Dynamic response of desert wetlands to abrupt climate change
Radiocarbon dating of late quaternary sediments using fossil gastropod shells
Early Upper Paleolithic chronology in the Levant
A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado
The Ziegler Reservoir fossil site near Snowmass Village, Colorado (USA), provides a unique opportunity to reconstruct high-altitude paleoenvironmental conditions in the Rocky Mountains during the Last Interglacial Period. We used four different techniques to establish a chronological framework for the site. Radiocarbon dating of lake organics, bone collagen, and shell carbonate, and in situ cosmogenic 10 Be and 26 Al ages on a boulder on the cres…
Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado
The geologic setting of the Ziegler Reservoir fossil site is somewhat unusual — the sediments containing the Pleistocene fossils were deposited in a lake on top of a ridge. The lake basin was formed near Snowmass Village, Colorado (USA) when a glacier flowing down Snowmass Creek Valley became thick enough to overtop a low point in the eastern valley wall and entered the head of Brush Creek Valley. When the glacier retreated at about 155–130 ka, n…
Introduction to the Snowmastodon Project Special Volume The Snowmastodon Project
Studies of terrestrial biotic and environmental dynamics of Marine Oxygen Isotope Stage (MIS) 5, also called the Last Interglacial Period, provide insight into the effects of long-term climate change on Pleistocene ecosystems. In North America, however, there are relatively few fossil sites that definitively date to MIS 5. Even fewer contain multiple ecosystem components (vertebrates, invertebrates, plants) that have been studied in detail, and n…
Summary of the Snowmastodon Project Special Volume A high-elevation, multi-proxy biotic and environmental record of MIS 6–4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA
In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland…
Fossil wetlands in the deserts of the American southwest
Radiocarbon ages of terrestrial gastropods extend duration of ice-free conditions at the Two Creeks forest bed, Wisconsin, USA
Analysis of terrestrial gastropods that underlie the late Pleistocene Two Creeks forest bed (~ 13,800–13,500 cal yr BP) in eastern Wisconsin, USA provides evidence for a mixed tundra-taiga environment prior to formation of the taiga forest bed. Ten new AMS 14 C analyses on terrestrial gastropod shells indicate the mixed tundra-taiga environment persisted from ~ 14,500 to 13,900 cal yr BP. The Twocreekan climatic substage, representing ice-free co…
Assessing Open-System Behavior of 14 C in Terrestrial Gastropod Shells
In order to assess open-system behavior of radiocarbon in fossil gastropod shells, we measured the 14 C activity on 10 aliquots of shell material recovered from Illinoian (~190–130 ka) and pre-Illinoian (~800 ka) loess and lacustrine deposits in the Midwestern USA. Eight of the 10 aliquots yielded measurable 14 C activities that ranged from 0.25 to 0.53 percent modern carbon (pMC), corresponding to apparent 14 C ages between 48.2 and 42.1 ka. Thi…
Extraction of In Situ Cosmogenic 14 C from Olivine
Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon ( in situ 14 C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14 C from olivine ((Fe,Mg) 2 SiO 4 ). We were able to extract a stable and reproducible in situ 14 C co…
A Simplified In Situ Cosmogenic 14 C Extraction System
We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 ± 11) x 10 3 atoms (1 σ; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14 C, but is typically 3 atoms g –1 or more. The new system is relatively small and easy to construct, costs significantly less than the original in si…
Development of low-background vacuum extraction and graphitization systems for 14C dating of old (40–60 ka) samples
On Correcting 14 C Ages of Gastropod Shell Carbonate for Fractionation
Correcting the 14 C age of a sample for fractionation is straightforward if the measured carbon was derived entirely from the atmosphere, either directly or through chemical and/or biological reactions that originated with atmospheric carbon. This correction is complicated in the case of gastropods that incorporate carbon from limestone or secondary carbonate (e.g. soil carbonate) during shell formation. The carbon isotopic composition of such ga…
Early Upper Paleolithic chronology in the Levant
On Correcting 14 C Ages of Gastropod Shell Carbonate for Fractionation
Correcting the 14 C age of a sample for fractionation is straightforward if the measured carbon was derived entirely from the atmosphere, either directly or through chemical and/or biological reactions that originated with atmospheric carbon. This correction is complicated in the case of gastropods that incorporate carbon from limestone or secondary carbonate (e.g. soil carbonate) during shell formation. The carbon isotopic composition of such ga…
A Simplified In Situ Cosmogenic 14 C Extraction System
We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 ± 11) x 10 3 atoms (1 σ; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14 C, but is typically 3 atoms g –1 or more. The new system is relatively small and easy to construct, costs significantly less than the original in si…
Assessing Open-System Behavior of 14 C in Terrestrial Gastropod Shells
In order to assess open-system behavior of radiocarbon in fossil gastropod shells, we measured the 14 C activity on 10 aliquots of shell material recovered from Illinoian (~190–130 ka) and pre-Illinoian (~800 ka) loess and lacustrine deposits in the Midwestern USA. Eight of the 10 aliquots yielded measurable 14 C activities that ranged from 0.25 to 0.53 percent modern carbon (pMC), corresponding to apparent 14 C ages between 48.2 and 42.1 ka. Thi…
On Correcting 14 C Ages of Gastropod Shell Carbonate for Fractionation
Correcting the 14 C age of a sample for fractionation is straightforward if the measured carbon was derived entirely from the atmosphere, either directly or through chemical and/or biological reactions that originated with atmospheric carbon. This correction is complicated in the case of gastropods that incorporate carbon from limestone or secondary carbonate (e.g. soil carbonate) during shell formation. The carbon isotopic composition of such ga…
Development of low-background vacuum extraction and graphitization systems for 14C dating of old (40–60 ka) samples
Extraction of In Situ Cosmogenic 14 C from Olivine
Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon ( in situ 14 C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14 C from olivine ((Fe,Mg) 2 SiO 4 ). We were able to extract a stable and reproducible in situ 14 C co…
A Simplified In Situ Cosmogenic 14 C Extraction System
We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 ± 11) x 10 3 atoms (1 σ; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14 C, but is typically 3 atoms g –1 or more. The new system is relatively small and easy to construct, costs significantly less than the original in si…
Assessing Open-System Behavior of 14 C in Terrestrial Gastropod Shells
In order to assess open-system behavior of radiocarbon in fossil gastropod shells, we measured the 14 C activity on 10 aliquots of shell material recovered from Illinoian (~190–130 ka) and pre-Illinoian (~800 ka) loess and lacustrine deposits in the Midwestern USA. Eight of the 10 aliquots yielded measurable 14 C activities that ranged from 0.25 to 0.53 percent modern carbon (pMC), corresponding to apparent 14 C ages between 48.2 and 42.1 ka. Thi…
Radiocarbon ages of terrestrial gastropods extend duration of ice-free conditions at the Two Creeks forest bed, Wisconsin, USA
Analysis of terrestrial gastropods that underlie the late Pleistocene Two Creeks forest bed (~ 13,800–13,500 cal yr BP) in eastern Wisconsin, USA provides evidence for a mixed tundra-taiga environment prior to formation of the taiga forest bed. Ten new AMS 14 C analyses on terrestrial gastropod shells indicate the mixed tundra-taiga environment persisted from ~ 14,500 to 13,900 cal yr BP. The Twocreekan climatic substage, representing ice-free co…
Fossil wetlands in the deserts of the American southwest
A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado
The Ziegler Reservoir fossil site near Snowmass Village, Colorado (USA), provides a unique opportunity to reconstruct high-altitude paleoenvironmental conditions in the Rocky Mountains during the Last Interglacial Period. We used four different techniques to establish a chronological framework for the site. Radiocarbon dating of lake organics, bone collagen, and shell carbonate, and in situ cosmogenic 10 Be and 26 Al ages on a boulder on the cres…
Geologic setting and stratigraphy of the Ziegler Reservoir fossil site, Snowmass Village, Colorado
The geologic setting of the Ziegler Reservoir fossil site is somewhat unusual — the sediments containing the Pleistocene fossils were deposited in a lake on top of a ridge. The lake basin was formed near Snowmass Village, Colorado (USA) when a glacier flowing down Snowmass Creek Valley became thick enough to overtop a low point in the eastern valley wall and entered the head of Brush Creek Valley. When the glacier retreated at about 155–130 ka, n…
Introduction to the Snowmastodon Project Special Volume The Snowmastodon Project
Studies of terrestrial biotic and environmental dynamics of Marine Oxygen Isotope Stage (MIS) 5, also called the Last Interglacial Period, provide insight into the effects of long-term climate change on Pleistocene ecosystems. In North America, however, there are relatively few fossil sites that definitively date to MIS 5. Even fewer contain multiple ecosystem components (vertebrates, invertebrates, plants) that have been studied in detail, and n…
Summary of the Snowmastodon Project Special Volume A high-elevation, multi-proxy biotic and environmental record of MIS 6–4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA
In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011, construction at Ziegler Reservoir near Snowmass Village, Colorado (USA) revealed a nearly continuous, lacustrine/wetland…
Dynamic response of desert wetlands to abrupt climate change
Radiocarbon dating of late quaternary sediments using fossil gastropod shells
Early Upper Paleolithic chronology in the Levant
On the importance of stratigraphic control for vertebrate fossil sites in Channel Islands National Park, California, USA
Activation of a small ephemeral lake in southern Jordan during the last full glacial period and its paleoclimatic implications
Playas, or ephemeral lakes, are one of the most common depositional environments in arid and semiarid lands worldwide. Playa deposits, however, have mostly been avoided as paleoclimatic archives because they typically contain exceptionally low concentrations of organic material, making 14 C dating difficult. Here, we describe a technique for concentrating organic matter in sediments for radiocarbon dating and apply it to playa sediments recovered…
Origin of last-glacial loess in the western Yukon-Tanana Upland, central Alaska, USA
Loess is widespread over Alaska, and its accumulation has traditionally been associated with glacial periods. Surprisingly, loess deposits securely dated to the last glacial period are rare in Alaska, and paleowind reconstructions for this time period are limited to inferences from dune orientations. We report a rare occurrence of loess deposits dating to the last glacial period, ~19 ka to ~12 ka, in the Yukon-Tanana Upland. Loess in this area is…
Overview of the oxygen isotope systematics of land snails from North America
Continental paleoclimate proxies with near-global coverage are rare. Land snail δ 18 O is one of the few proxies abundant in Quaternary sediments ranging from the tropics to the high Arctic tundra. However, its application in paleoclimatology remains difficult, attributable in part to limitations in published calibration studies. Here we present shell δ 18 O of modern small ( 18 O at a coarse scale. This transect is augmented by published δ 18 O …
Desert wetlands record hydrologic variability within the Younger Dryas chronozone, Mojave Desert, USA
One of the enduring questions in the field of paleohydrology is how quickly desert wetland ecosystems responded to past episodes of abrupt climate change. Recent investigations in the Las Vegas Valley of southern Nevada have revealed that wetlands expanded and contracted on millennial and sub-millennial timescales in response to changes in climate during the late Quaternary. Here, we evaluate geologic evidence from multiple localities in the Moja…
Aeolian sediments in paleowetland deposits of the Las Vegas Formation
The Las Vegas Formation (LVF) is a well-characterized sequence of groundwater discharge (GWD) deposits exposed in and around the Las Vegas Valley in southern Nevada. Nearly monolithologic bedrock surrounds the valley, which provides an excellent opportunity to test the hypothesis that GWD deposits include an aeolian component. Mineralogical data indicate that the LVF sediments are dominated by carbonate minerals, similar to the local bedrock, but…
Oxygen isotopes in terrestrial gastropod shells track Quaternary climate change in the American Southwest
Recent studies have shown the oxygen isotopic composition (δ 18 O) of modern terrestrial gastropod shells is determined largely by the δ 18 O of precipitation. This implies that fossil shells could be used to reconstruct the δ 18 O of paleo-precipitation as long as the isotopic system, including the hydrologic pathways of the local watershed and the gastropod systematics, is well understood. In this study, we measured the δ 18 O values of 456 ind…
Evidence of humans in North America during the Last Glacial Maximum
Early footsteps in the Americas Despite a plethora of archaeological research over the past century, the timing of human migration into the Americas is still far from resolved. In a study of exposed outcrops of Lake Otero in White Sands National Park in New Mexico, Bennett et al . reveal numerous human footprints dating to about 23,000 to 21,000 years ago. These finds indicate the presence of humans in North America for approximately two millenni…
Reply to “Evidence for Humans at White Sands National Park during the Last Glacial Maximum Could Actually be for Clovis People ∼13,000 Years Ago” by C. Vance Haynes, Jr
Bennett et al. (2021, Science 373, 1528–1531) reported that ancient human footprints discovered in White Sands National Park, New Mexico date to between ∼23,000 and 21,000 years ago. Haynes (2022, PaleoAmerica, this issue) proposes two alternate hypotheses to explain the antiquity of the footprints. One is that they were made by humans crossing over older sediments sometime during the Holocene. This is incorrect as there are Pleistocene megafauna…
Late glacial–Younger Dryas climate in interior Alaska as inferred from the isotope values of land snail shells
The isotope values of fossil snail shells can be important archives of climate. Here, we present the first carbon (δ 13 C) and oxygen (δ 18 O) isotope values of snail shells in interior Alaska to explore changes in vegetation and humidity through the late-glacial period. Snail shell δ 13 C values were relatively consistent through the late glacial. However, late-glacial shell δ 13 C values are 2.8‰ higher than those of modern shells. This offset …
The Geochronology of White Sands Locality 2 is Resolved
Rhode et al. [2024. “Unresolved: Persistent problems with the White Sands Locality 2 Geochronology.” PaleoAmerica] contend there are many “unresolved issues” with the geochronology of White Sands National Park (WHSA) Locality 2. They suggest there are substantial age offsets due to hard-water effects in the aquatic plants that were dated and that radiocarbon ages of pollen may be anomalously old due to reworking. In their view, the luminescence a…
Geology and Paleoclimatology Research (20 obras) · Geography (14 obras) · Geology (14 obras) · Paleontology (12 obras) · Geology (10 obras) · Radiocarbon dating (10 obras) · Isotope Analysis in Ecology (9 obras) · Pleistocene-Era Hominins and Archaeology (9 obras) · Archaeology (8 obras) · Biology (8 obras)