Thomas A Ager
Biographic Data
| ID | 6372387 |
|---|---|
| NAME | Thomas A Ager |
| GIVEN NAMES | Thomas A |
| FAMILY NAME | Ager |
| SIGNATURE | AGER T A |
| AFFILIATIONS | United States Geological Survey |
| ORCID | 0000-0002-5029-7581 |
| VERIFIED | Yes |
| TOTAL WORKS | 11 |
| TOTAL CITATIONS | 0 |
| WORKS AS AUTHOR | 11 |
| WORKS AS EDITOR | 0 |
| FIRST PUBLICATION YEAR | 1990 |
| LATEST PUBLICATION YEAR | 2014 |
| H-INDEX | 0 |
High-elevation paleoenvironmental change during MIS 6–4 in the central Rockies of Colorado as determined from pollen analysis
Paleoecological studies from Rocky Mountain (USA) high elevations encompassing the previous interglacial (MIS 5e) are rare. The ~10-m composite profile from the Ziegler Reservoir fossil site (2705 m asl) of central Colorado allows us to determine paleoenvironments from Marine Oxygen Isotope Stages (MIS) 6– 4 using pollen zones that are approximately equivalent to marine oxygen isotope stages. During Pollen Zone (PZ) 6 time, pollen assemblages dom…
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…
Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska
An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ∼12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (∼12,900 cal yr BP) was pine woodland ( Pinus contorta ) with alder ( Alnus ), sedges (Cyperaceae) and ferns (Polypodiaceae type). B…
Marine tephrochronology of the Mt. Edgecumbe Volcanic Field, Southeast Alaska, USA
The Mt. Edgecumbe Volcanic Field (MEVF), located on Kruzof Island near Sitka Sound in southeast Alaska, experienced a large multiple-stage eruption during the last glacial maximum (LGM)-Holocene transition that generated a regionally extensive series of compositionally similar rhyolite tephra horizons and a single well-dated dacite (MEd) tephra. Marine sediment cores collected from adjacent basins to the MEVF contain both tephra-fall and pyroclas…
Holocene thermal maximum in the western Arctic (0–180°W)
Recurring middle Pleistocene outburst floods in east-central Alaska
Recurring glacial outburst floods from the Yukon-Tanana Upland are inferred from sediments exposed along the Yukon River near the mouth of Charley River in east-central Alaska. Deposits range from imbricate gravel and granules indicating flow locally extending up the Yukon valley, to more distal sediments consisting of at least 10 couplets of planar sands, granules, and climbing ripples with up-valley paleocurrent indicators overlain by massive s…
Late Quaternary vegetation and climate history of the central Bering land bridge from St. Michael Island, western Alaska
Pollen analysis of a sediment core from Zagoskin Lake on St. Michael Island, northeast Bering Sea, provides a history of vegetation and climate for the central Bering land bridge and adjacent western Alaska for the past ≥30,000 14 C yr B.P. During the late middle Wisconsin interstadial (≥30,000–26,000 14 C yr B.P.) vegetation was dominated by graminoid-herb tundra with willows ( Salix ) and minor dwarf birch ( Betula nana ) and Ericales. During t…
A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska
Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the m…
Pliocene terrace gravels of the ancestral Yukon River near Circle, Alaska
Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska
The Hayes Tephra Deposits, and Upper Holocene Marker Horizon in South-Central Alaska
The most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to be…
No prominent works on this page.
The Hayes Tephra Deposits, and Upper Holocene Marker Horizon in South-Central Alaska
The most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to be…
Pliocene terrace gravels of the ancestral Yukon River near Circle, Alaska
Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska
Recurring middle Pleistocene outburst floods in east-central Alaska
Recurring glacial outburst floods from the Yukon-Tanana Upland are inferred from sediments exposed along the Yukon River near the mouth of Charley River in east-central Alaska. Deposits range from imbricate gravel and granules indicating flow locally extending up the Yukon valley, to more distal sediments consisting of at least 10 couplets of planar sands, granules, and climbing ripples with up-valley paleocurrent indicators overlain by massive s…
Late Quaternary vegetation and climate history of the central Bering land bridge from St. Michael Island, western Alaska
Pollen analysis of a sediment core from Zagoskin Lake on St. Michael Island, northeast Bering Sea, provides a history of vegetation and climate for the central Bering land bridge and adjacent western Alaska for the past ≥30,000 14 C yr B.P. During the late middle Wisconsin interstadial (≥30,000–26,000 14 C yr B.P.) vegetation was dominated by graminoid-herb tundra with willows ( Salix ) and minor dwarf birch ( Betula nana ) and Ericales. During t…
A late Quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska
Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the m…
Holocene thermal maximum in the western Arctic (0–180°W)
Postglacial vegetation history of Mitkof Island, Alexander Archipelago, southeastern Alaska
An AMS radiocarbon-dated pollen record from a peat deposit on Mitkof Island, southeastern Alaska provides a vegetation history spanning ∼12,900 cal yr BP to the present. Late Wisconsin glaciers covered the entire island; deglaciation occurred > 15,400 cal yr BP. The earliest known vegetation to develop on the island (∼12,900 cal yr BP) was pine woodland ( Pinus contorta ) with alder ( Alnus ), sedges (Cyperaceae) and ferns (Polypodiaceae type). B…
Marine tephrochronology of the Mt. Edgecumbe Volcanic Field, Southeast Alaska, USA
The Mt. Edgecumbe Volcanic Field (MEVF), located on Kruzof Island near Sitka Sound in southeast Alaska, experienced a large multiple-stage eruption during the last glacial maximum (LGM)-Holocene transition that generated a regionally extensive series of compositionally similar rhyolite tephra horizons and a single well-dated dacite (MEd) tephra. Marine sediment cores collected from adjacent basins to the MEVF contain both tephra-fall and pyroclas…
High-elevation paleoenvironmental change during MIS 6–4 in the central Rockies of Colorado as determined from pollen analysis
Paleoecological studies from Rocky Mountain (USA) high elevations encompassing the previous interglacial (MIS 5e) are rare. The ~10-m composite profile from the Ziegler Reservoir fossil site (2705 m asl) of central Colorado allows us to determine paleoenvironments from Marine Oxygen Isotope Stages (MIS) 6– 4 using pollen zones that are approximately equivalent to marine oxygen isotope stages. During Pollen Zone (PZ) 6 time, pollen assemblages dom…
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…
Geology and Paleoclimatology Research (11 works) · Geology (9 works) · Holocene (7 works) · Paleontology (7 works) · Biology (6 works) · Climate change and permafrost (5 works) · Oceanography (5 works) · Arctic (4 works) · Ecology (4 works) · Glacial period (4 works)