linda heusser - Academia.edu (original) (raw)
Papers by linda heusser
The climatic effects of major geologic events of the last 6 m.y., such as the variations in arcti... more The climatic effects of major geologic events of the last 6 m.y., such as the variations in arctic and Antarctic icecaps and the uplift of major mountain ranges, are reasonably well documented in the marine realm. On land, however, such evidence is limited, and chronostratigraphic control is minimal. Only ~12 widely separated floras are available to reconstruct discrete events in the evolution of vegetation and climate of California and Oregon forests during the late Neogene, an interval in which major climatic changes are reflected in the replacement of Miocene mesophytic forests by temperate coniferous forests (Axelrod, 1977). Cores taken on the California margin during Leg 167 provide an opportunity to continuously monitor vegetation of the northwest coast of North America (using marine pollen assemblages), to set the terrestrial vegetation and climate records in accurate age frameworks provided by other components in the cores, and to directly relate late Neogene changes in ocea...
A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water ... more A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water depth) and TN062 0550 (40.9 deg. N,124.6 deg. W, 570 m water depth), and a pollen proxy for summer moisture from terrestrial bog core SB70-1 (40.3 deg. N, 123.4 deg. W, 910 m altitude), together reveal a detailed record of climate change in the Eel River basin area of northernmost California during the past 3,500 years. Age models for all three cores are well constrained by AMS dates, with sample spacing varying from ca. 150 years at ODP 1019 to between 30 and 50 years in both TN062 0550 and SB70-1. As indicated by the diatom proxy for the warm waters of the Central Gyre, Pseudoeunotia doliolus, a late Holocene trend toward warmer fall SST's began approximately 1,000 years earlier at the more offshore (60 km offshore) ODP Site 1019 (ca. 3.4 ka), than it did in the more coastal (33 km offshore) piston core TN062 0550 (ca. 2.4 ka). This diatom proxy suggests that a pronounced offshore...
Proceedings of the Ocean Drilling Program, Scientific Results, 2000
Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9... more Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9504-17 provide continuous, chronostratigraphically controlled proxy vegetation and climate data for coastal northwest North America for the last~ 500 ky Systematic changes in the representation of the diagnostic components of northern California plant assemblages clearly show orbital-scale variations. Interglacials are all marked by an abrupt increase in alder followed by expansion of lowland oak woodland ...
Quaternary International
Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-res... more Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-resolution record of the climate and oceanography of coastal northernmost California during the past ~7.34 kyr. Chronology established by nine AMS ages on a combination of planktic foraminifers, bivalve shell fragments, and wood yields a mean sedimentation rate of 103 cm kyr À1. Marine proxies (diatoms and silicoflagellates) and pollen transported by the nearby Eel River reveal a stepwise development of both modern offshore surface water oceanography and coastal arboreal ecosystems. Beginning at ~5.4 cal ka the relative abundance of coastal redwood pollen, a proxy for coastal fog, displays a two fold increase suggesting enhanced coastal upwelling. A decline in the relative contribution of subtropical diatoms at ~5.0 cal ka implies cooling of sea surface temperatures (SSTs). At ~3.6 cal ka an increase in the relative abundance of alder and oak at the expense of coastal redwood likely signals intensified riverine transport of pollen from inland environments. Cooler offshore SSTs and increased precipitation characterize the interval between ~3.6 and 2.8 cal ka. A rapid, stepwise change in coastal climatology and oceanography occurs between ~2.8 and 2.6 cal ka that suggests an enhanced expression of modern Pacific Decadal Oscillation-like (PDO) cycles. A threefold increase in the relative abundance of the subtropical diatom Fragilariopsis doliolus at 2.8 cal ka appears to mark an abrupt warming of winter SSTs. Soon afterwards at 2.6 cal ka, a two fold increase in the relative abundance of coastal redwood pollen is suggestive of an abrupt intensification of spring upwelling. After ~2.8 cal ka a sequence of cool-warm, PDO-like cycles occurs wherein cool cycles are characterized by relative abundance increases in coastal redwood pollen and decreased contributions of subtropical diatoms, whereas opposite proxy trends distinguish warm cycles. Published by Elsevier Ltd.
Proceedings of the Ocean Drilling Program
Pollen data (159 samples taken at ~<IOOO yr intervals) provide the first continuous, chronologica... more Pollen data (159 samples taken at ~<IOOO yr intervals) provide the first continuous, chronologically controlled record of southern California terrestrial environments over the past 160 k.y., a record that is directly correlated with changes in the marine environment inferred from organic and inorganic components of the same sediment samples. In the well-laminated sediments deposited during the last interglacial interval, pollen assemblages are characterized by Quercus and other taxa similar to those of present arid coastal biomes (e.g., oak woodland, chaparral, coastal sage scrub, and salt marsh). Pollen assemblages in the massive glacial sediments, dominated by conifers (referable to the Taxodiaceae, Cupressaceae, Taxaceae, and Pinaceae families) imply altitudinal and latitudinal expansion of montane conifer woodland and forest associations (e.g., juniper woodlands and yellow pine forests of the Transverse Ranges). Variable representation of oak woodland and coniferous forests characterizes interstadials and stadials. During the last glacial maximum on the south coast of California, mean annual temperature and effective precipitation estimates inferred from pollen data in Santa Barbara Basin are ~5°C and-1000 mm, respectively. Interglacial temperatures and evapotranspiration were comparable to or possibly higher than at present. High-frequency variability in the pollen/vegetation assemblages from Ocean Drilling Program Hole 893A implies frequent and rapid change between these two climatic endmembers throughout the last 160 k.y. For example, following an abrupt warming at-14 k.y., a brief mesic, cooling event precedes the development of Holocene interglacial conditions. Systematic variations in the pollen assemblages deposited in Santa Barbara Basin are similar in amplitude and duration to changes reconstructed from oxygen isotopes in the same sediment samples. The apparent synchroneity of the terrestrial (pollen/ vegetation of south coastal California) and marine (oxygen isotope) proxy climate signals from Hole 893A concurs with previous results from the North and South Pacific which showed similar rapid responses of terrestrial ecosystems to global climate change during the last glacial cycle.
Proceedings of the Ocean Drilling Program
Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9... more Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9504-17 provide continuous, chronostratigraphically controlled proxy vegetation and climate data for coastal northwest North America for the last ~500 k.y. Systematic changes in the representation of the diagnostic components of northern California plant assemblages clearly show orbital-scale variations. Interglacials are all marked by an abrupt increase in alder followed by expansion of lowland oak woodland and redwood forests. Glacials are dominated by montane forest and woodland assemblages. This sequence reflects large-scale climatic controls (e.g., orbital-scale variation in insolation and Northern Hemisphere ice sheets) in western North America over the last five glacial cycles. Regional climatic control (variations in sea-surface conditions) is implied by the differential development of xeric oak and mesic redwood communities.
Agu Fall Meeting Abstracts, Dec 1, 2003
Diatom data suggest that a late Holocene trend toward warmer fall sea surface temperatures (SST) ... more Diatom data suggest that a late Holocene trend toward warmer fall sea surface temperatures (SST) began approximately 1,000 yr earlier (c a. 3.,400 cal yr B.P.) at ODP Site 1019 (60 km offshore), than it did in the more coastal site of piston core TN062 0550 (33 km offshore). A pronounced offshore-nearshore SST gradient appears to have existed between these two core sites until ca. 1,400 cal yr B.P. (or A.D. 600), after which it abruptly collapsed. Coincident with this collapse, Douglas fir pollen abruptly increased from c a. 15% to nearly 40% of the pollen assemblage in Schelling's bog in the nearby Coast Ranges of northern California, arguing for a sudden increase in summer moisture. Regional cooling may have caused a shift in the mean summer position of the Subtropical High further to the south between ca. A.D. 500 and 600. During the past 1,400 yr, diatom data suggest cooling of SST between ca. A.D. 600 and 900, a pronounced warming between ca. A.D. 950 and 1200 (the Medieval Warm Period?), and another cooling between ca. A.D. 1350 and 1800 (the Little Ice Age?). In general, greater relative abundance of Douglas fir pollen in the Schelling's bog record coincident with these cooler SST intervals implies increased summer moisture onshore. Increased relative abundance of oak pollen between ca. A.D. 850 and 1050, and A.D. 1150 and 1200 suggest that drier summer conditions coincided with warmer fall SST offshore.
Agu Fall Meeting Abstracts, Dec 1, 2003
Between 15 Ma and 5 Ma the vegetation of the western US suffered a profound transition from summe... more Between 15 Ma and 5 Ma the vegetation of the western US suffered a profound transition from summer-wet to summer-dry flora. In the middle Miocene extensive deciduous forests covered the region, reminiscent of modern forests of the SE United States. By the beginning of the ...
Review of Palaeobotany and Palynology, 1990
Pollen, radiolarian and oxygen isotope analyses of deep-sea sediment cores V28-304 and RC14-99 pr... more Pollen, radiolarian and oxygen isotope analyses of deep-sea sediment cores V28-304 and RC14-99 provide continuous chronostratigraphically-controlled records of the regional vegetation of the Pacific coast of the Japanese archipelago over the last 150,000 years. These detailed time series (sampled at ~2000 year-intervals) chronical the changing composition of temperate forests of Japan in which gymnosperms are more abundant than angiosperms. Pinus and Picea characterize glacial intervals and the expansion of Cryptomeria, along with Sciadopitys, characterizes nonglacial intervals between ~ 120,000 and .
Http Dx Doi Org 10 1080 01916122 1984 9989279, Aug 24, 2010
Quaternary Science Reviews, 2016
We present the first, well-dated, high-resolution record of vegetation and landscape change from ... more We present the first, well-dated, high-resolution record of vegetation and landscape change from Serbia, which spans the past 500 years. Biological proxies (pollen, spores, and charcoal), geochemical analysis through X-ray Fluorescence (XRF), and a detailed chronology based on AMS 14C dating from a western Serbian sinkhole core suggest complex woodland-grassland dynamics and strong erosional signals throughout the Little Ice Age (LIA). An open landscape with prominent steppe vegetation (e.g. Poaceae, Chenopodiaceae) and minor woodland exists during 1540-1720 CE (early LIA), while the late LIA (1720-1850 CE) in this record shows higher tree percentages possibly due to increased moisture availability. The post LIA Era (1850-2012 CE) brings a disturbed type of vegetation with the presence of weedy genera and an increase in regional woodland. Anthropogenic indicators for agricultural, pastoral and fire practices in the region together attest to the dominant role of humans in shaping this Balkan landscape throughout the interval. The changing nature of human interference, potentially as a response to underlying climatic transitions, is evident through large-scale soil depletion resulting from grazing and land clearance during the early LIA and stabilization of arable lands during the late and post-LIA eras.
Geology, 1997
Century-long variations in coastal California vegetation inferred from polliniferous sediments de... more Century-long variations in coastal California vegetation inferred from polliniferous sediments deposited in the Santa Barbara basin record a succession of brief (<200 yr duration) climatic events that recurred at ~1000 yr intervals (
Quaternary International, 2015
Initial Reports of the Deep Sea Drilling Project, 1986
At all sites drilled during Deep Sea Drilling Project Leg 96, we penetrated late Quaternary sedim... more At all sites drilled during Deep Sea Drilling Project Leg 96, we penetrated late Quaternary sediments, encountering Ericson Zones W, X, Y, and Z (early Wisconsin glacial through Holocene). Chronostratigraphic studies on the Mississippi Fan were limited to foraminifer and calcareous nannofossil biostratigraphy because of very high sedimentation rates (6-11 m/1000 yr.). The main focus of interdisciplinary stratigraphic studies was Site 619 in the Pigmy Basin. At Site 619, an almost continuous sequence of hemipelagic sediments was recovered from Ericson Zones X through Z. Detailed studies at this site include: biostratigraphy (foraminifers, calcareous nannofossils, palynology), oxygen-isotope stratigraphy, tephrochronology, and magnetostratigraphy. Comparison of the curves shows a close correlation between biostratigraphy, oxygenisotope stages, and tephrochronology.
Geology, 1993
Two independent paleoclimatic records from the Pacific coast of Canada indicate that a late-glaci... more Two independent paleoclimatic records from the Pacific coast of Canada indicate that a late-glacial warming trend was interrupted by a return to colder conditions between about 11,000 and 10,200 radiocarbon yr B.P., correlative with the classical Younger Dryas chronozone of the North Atlantic region. Fossil benthic foraminifera from three cores from the continental shelf dated by accelerator mass spectrometry show peak abundances of the coldwater indicator species Cassidulina reniforme at this time. Fossil-pollen spectra from two sites on the Queen Charlotte Islands record a shift from forest to open, herb-rich vegetation after 11,100 yr B.P., probably in response to colder and wetter conditions identified by pollen-climate transfer functions. These preliminary data for a cold oscillation between ca. 11000 and 10 000 yr ago in the northeast Pacific argue that this deglacial phenomenon was not restricted to the North Atlantic, but was a hemispheric-and possibly global-event.
Résumé/Abstract Sediments from five Leg 167 drill sites and three piston cores were analyzed for ... more Résumé/Abstract Sediments from five Leg 167 drill sites and three piston cores were analyzed for C and CaCO 3. Oxygen isotope stratigraphy on benthic foraminifers was used to assign age models to these sedimentary records. We find that the northern and central California margin is characterized by ky-scale events that can be found in both the CaCO 3 and C or time series. We show that the CaCO 3 events are caused by changes in CaCO 3 production by plankton, not by dissolution. We also show that these CaCO 3 events occur ...
The climatic effects of major geologic events of the last 6 m.y., such as the variations in arcti... more The climatic effects of major geologic events of the last 6 m.y., such as the variations in arctic and Antarctic icecaps and the uplift of major mountain ranges, are reasonably well documented in the marine realm. On land, however, such evidence is limited, and chronostratigraphic control is minimal. Only ~12 widely separated floras are available to reconstruct discrete events in the evolution of vegetation and climate of California and Oregon forests during the late Neogene, an interval in which major climatic changes are reflected in the replacement of Miocene mesophytic forests by temperate coniferous forests (Axelrod, 1977). Cores taken on the California margin during Leg 167 provide an opportunity to continuously monitor vegetation of the northwest coast of North America (using marine pollen assemblages), to set the terrestrial vegetation and climate records in accurate age frameworks provided by other components in the cores, and to directly relate late Neogene changes in ocea...
A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water ... more A diatom proxy for SST from two offshore cores, ODP 1019 (41.7 deg. N, 124.9 deg. W, 980 m water depth) and TN062 0550 (40.9 deg. N,124.6 deg. W, 570 m water depth), and a pollen proxy for summer moisture from terrestrial bog core SB70-1 (40.3 deg. N, 123.4 deg. W, 910 m altitude), together reveal a detailed record of climate change in the Eel River basin area of northernmost California during the past 3,500 years. Age models for all three cores are well constrained by AMS dates, with sample spacing varying from ca. 150 years at ODP 1019 to between 30 and 50 years in both TN062 0550 and SB70-1. As indicated by the diatom proxy for the warm waters of the Central Gyre, Pseudoeunotia doliolus, a late Holocene trend toward warmer fall SST's began approximately 1,000 years earlier at the more offshore (60 km offshore) ODP Site 1019 (ca. 3.4 ka), than it did in the more coastal (33 km offshore) piston core TN062 0550 (ca. 2.4 ka). This diatom proxy suggests that a pronounced offshore...
Proceedings of the Ocean Drilling Program, Scientific Results, 2000
Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9... more Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9504-17 provide continuous, chronostratigraphically controlled proxy vegetation and climate data for coastal northwest North America for the last~ 500 ky Systematic changes in the representation of the diagnostic components of northern California plant assemblages clearly show orbital-scale variations. Interglacials are all marked by an abrupt increase in alder followed by expansion of lowland oak woodland ...
Quaternary International
Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-res... more Piston core TN062-O550, collected about 33 km offshore of Eureka, California, contains a high-resolution record of the climate and oceanography of coastal northernmost California during the past ~7.34 kyr. Chronology established by nine AMS ages on a combination of planktic foraminifers, bivalve shell fragments, and wood yields a mean sedimentation rate of 103 cm kyr À1. Marine proxies (diatoms and silicoflagellates) and pollen transported by the nearby Eel River reveal a stepwise development of both modern offshore surface water oceanography and coastal arboreal ecosystems. Beginning at ~5.4 cal ka the relative abundance of coastal redwood pollen, a proxy for coastal fog, displays a two fold increase suggesting enhanced coastal upwelling. A decline in the relative contribution of subtropical diatoms at ~5.0 cal ka implies cooling of sea surface temperatures (SSTs). At ~3.6 cal ka an increase in the relative abundance of alder and oak at the expense of coastal redwood likely signals intensified riverine transport of pollen from inland environments. Cooler offshore SSTs and increased precipitation characterize the interval between ~3.6 and 2.8 cal ka. A rapid, stepwise change in coastal climatology and oceanography occurs between ~2.8 and 2.6 cal ka that suggests an enhanced expression of modern Pacific Decadal Oscillation-like (PDO) cycles. A threefold increase in the relative abundance of the subtropical diatom Fragilariopsis doliolus at 2.8 cal ka appears to mark an abrupt warming of winter SSTs. Soon afterwards at 2.6 cal ka, a two fold increase in the relative abundance of coastal redwood pollen is suggestive of an abrupt intensification of spring upwelling. After ~2.8 cal ka a sequence of cool-warm, PDO-like cycles occurs wherein cool cycles are characterized by relative abundance increases in coastal redwood pollen and decreased contributions of subtropical diatoms, whereas opposite proxy trends distinguish warm cycles. Published by Elsevier Ltd.
Proceedings of the Ocean Drilling Program
Pollen data (159 samples taken at ~<IOOO yr intervals) provide the first continuous, chronologica... more Pollen data (159 samples taken at ~<IOOO yr intervals) provide the first continuous, chronologically controlled record of southern California terrestrial environments over the past 160 k.y., a record that is directly correlated with changes in the marine environment inferred from organic and inorganic components of the same sediment samples. In the well-laminated sediments deposited during the last interglacial interval, pollen assemblages are characterized by Quercus and other taxa similar to those of present arid coastal biomes (e.g., oak woodland, chaparral, coastal sage scrub, and salt marsh). Pollen assemblages in the massive glacial sediments, dominated by conifers (referable to the Taxodiaceae, Cupressaceae, Taxaceae, and Pinaceae families) imply altitudinal and latitudinal expansion of montane conifer woodland and forest associations (e.g., juniper woodlands and yellow pine forests of the Transverse Ranges). Variable representation of oak woodland and coniferous forests characterizes interstadials and stadials. During the last glacial maximum on the south coast of California, mean annual temperature and effective precipitation estimates inferred from pollen data in Santa Barbara Basin are ~5°C and-1000 mm, respectively. Interglacial temperatures and evapotranspiration were comparable to or possibly higher than at present. High-frequency variability in the pollen/vegetation assemblages from Ocean Drilling Program Hole 893A implies frequent and rapid change between these two climatic endmembers throughout the last 160 k.y. For example, following an abrupt warming at-14 k.y., a brief mesic, cooling event precedes the development of Holocene interglacial conditions. Systematic variations in the pollen assemblages deposited in Santa Barbara Basin are similar in amplitude and duration to changes reconstructed from oxygen isotopes in the same sediment samples. The apparent synchroneity of the terrestrial (pollen/ vegetation of south coastal California) and marine (oxygen isotope) proxy climate signals from Hole 893A concurs with previous results from the North and South Pacific which showed similar rapid responses of terrestrial ecosystems to global climate change during the last glacial cycle.
Proceedings of the Ocean Drilling Program
Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9... more Pollen analyses of sediments from Holes 1019C, 1019E, 1020C, and 1020D as well as piston Core EW9504-17 provide continuous, chronostratigraphically controlled proxy vegetation and climate data for coastal northwest North America for the last ~500 k.y. Systematic changes in the representation of the diagnostic components of northern California plant assemblages clearly show orbital-scale variations. Interglacials are all marked by an abrupt increase in alder followed by expansion of lowland oak woodland and redwood forests. Glacials are dominated by montane forest and woodland assemblages. This sequence reflects large-scale climatic controls (e.g., orbital-scale variation in insolation and Northern Hemisphere ice sheets) in western North America over the last five glacial cycles. Regional climatic control (variations in sea-surface conditions) is implied by the differential development of xeric oak and mesic redwood communities.
Agu Fall Meeting Abstracts, Dec 1, 2003
Diatom data suggest that a late Holocene trend toward warmer fall sea surface temperatures (SST) ... more Diatom data suggest that a late Holocene trend toward warmer fall sea surface temperatures (SST) began approximately 1,000 yr earlier (c a. 3.,400 cal yr B.P.) at ODP Site 1019 (60 km offshore), than it did in the more coastal site of piston core TN062 0550 (33 km offshore). A pronounced offshore-nearshore SST gradient appears to have existed between these two core sites until ca. 1,400 cal yr B.P. (or A.D. 600), after which it abruptly collapsed. Coincident with this collapse, Douglas fir pollen abruptly increased from c a. 15% to nearly 40% of the pollen assemblage in Schelling's bog in the nearby Coast Ranges of northern California, arguing for a sudden increase in summer moisture. Regional cooling may have caused a shift in the mean summer position of the Subtropical High further to the south between ca. A.D. 500 and 600. During the past 1,400 yr, diatom data suggest cooling of SST between ca. A.D. 600 and 900, a pronounced warming between ca. A.D. 950 and 1200 (the Medieval Warm Period?), and another cooling between ca. A.D. 1350 and 1800 (the Little Ice Age?). In general, greater relative abundance of Douglas fir pollen in the Schelling's bog record coincident with these cooler SST intervals implies increased summer moisture onshore. Increased relative abundance of oak pollen between ca. A.D. 850 and 1050, and A.D. 1150 and 1200 suggest that drier summer conditions coincided with warmer fall SST offshore.
Agu Fall Meeting Abstracts, Dec 1, 2003
Between 15 Ma and 5 Ma the vegetation of the western US suffered a profound transition from summe... more Between 15 Ma and 5 Ma the vegetation of the western US suffered a profound transition from summer-wet to summer-dry flora. In the middle Miocene extensive deciduous forests covered the region, reminiscent of modern forests of the SE United States. By the beginning of the ...
Review of Palaeobotany and Palynology, 1990
Pollen, radiolarian and oxygen isotope analyses of deep-sea sediment cores V28-304 and RC14-99 pr... more Pollen, radiolarian and oxygen isotope analyses of deep-sea sediment cores V28-304 and RC14-99 provide continuous chronostratigraphically-controlled records of the regional vegetation of the Pacific coast of the Japanese archipelago over the last 150,000 years. These detailed time series (sampled at ~2000 year-intervals) chronical the changing composition of temperate forests of Japan in which gymnosperms are more abundant than angiosperms. Pinus and Picea characterize glacial intervals and the expansion of Cryptomeria, along with Sciadopitys, characterizes nonglacial intervals between ~ 120,000 and .
Http Dx Doi Org 10 1080 01916122 1984 9989279, Aug 24, 2010
Quaternary Science Reviews, 2016
We present the first, well-dated, high-resolution record of vegetation and landscape change from ... more We present the first, well-dated, high-resolution record of vegetation and landscape change from Serbia, which spans the past 500 years. Biological proxies (pollen, spores, and charcoal), geochemical analysis through X-ray Fluorescence (XRF), and a detailed chronology based on AMS 14C dating from a western Serbian sinkhole core suggest complex woodland-grassland dynamics and strong erosional signals throughout the Little Ice Age (LIA). An open landscape with prominent steppe vegetation (e.g. Poaceae, Chenopodiaceae) and minor woodland exists during 1540-1720 CE (early LIA), while the late LIA (1720-1850 CE) in this record shows higher tree percentages possibly due to increased moisture availability. The post LIA Era (1850-2012 CE) brings a disturbed type of vegetation with the presence of weedy genera and an increase in regional woodland. Anthropogenic indicators for agricultural, pastoral and fire practices in the region together attest to the dominant role of humans in shaping this Balkan landscape throughout the interval. The changing nature of human interference, potentially as a response to underlying climatic transitions, is evident through large-scale soil depletion resulting from grazing and land clearance during the early LIA and stabilization of arable lands during the late and post-LIA eras.
Geology, 1997
Century-long variations in coastal California vegetation inferred from polliniferous sediments de... more Century-long variations in coastal California vegetation inferred from polliniferous sediments deposited in the Santa Barbara basin record a succession of brief (<200 yr duration) climatic events that recurred at ~1000 yr intervals (
Quaternary International, 2015
Initial Reports of the Deep Sea Drilling Project, 1986
At all sites drilled during Deep Sea Drilling Project Leg 96, we penetrated late Quaternary sedim... more At all sites drilled during Deep Sea Drilling Project Leg 96, we penetrated late Quaternary sediments, encountering Ericson Zones W, X, Y, and Z (early Wisconsin glacial through Holocene). Chronostratigraphic studies on the Mississippi Fan were limited to foraminifer and calcareous nannofossil biostratigraphy because of very high sedimentation rates (6-11 m/1000 yr.). The main focus of interdisciplinary stratigraphic studies was Site 619 in the Pigmy Basin. At Site 619, an almost continuous sequence of hemipelagic sediments was recovered from Ericson Zones X through Z. Detailed studies at this site include: biostratigraphy (foraminifers, calcareous nannofossils, palynology), oxygen-isotope stratigraphy, tephrochronology, and magnetostratigraphy. Comparison of the curves shows a close correlation between biostratigraphy, oxygenisotope stages, and tephrochronology.
Geology, 1993
Two independent paleoclimatic records from the Pacific coast of Canada indicate that a late-glaci... more Two independent paleoclimatic records from the Pacific coast of Canada indicate that a late-glacial warming trend was interrupted by a return to colder conditions between about 11,000 and 10,200 radiocarbon yr B.P., correlative with the classical Younger Dryas chronozone of the North Atlantic region. Fossil benthic foraminifera from three cores from the continental shelf dated by accelerator mass spectrometry show peak abundances of the coldwater indicator species Cassidulina reniforme at this time. Fossil-pollen spectra from two sites on the Queen Charlotte Islands record a shift from forest to open, herb-rich vegetation after 11,100 yr B.P., probably in response to colder and wetter conditions identified by pollen-climate transfer functions. These preliminary data for a cold oscillation between ca. 11000 and 10 000 yr ago in the northeast Pacific argue that this deglacial phenomenon was not restricted to the North Atlantic, but was a hemispheric-and possibly global-event.
Résumé/Abstract Sediments from five Leg 167 drill sites and three piston cores were analyzed for ... more Résumé/Abstract Sediments from five Leg 167 drill sites and three piston cores were analyzed for C and CaCO 3. Oxygen isotope stratigraphy on benthic foraminifers was used to assign age models to these sedimentary records. We find that the northern and central California margin is characterized by ky-scale events that can be found in both the CaCO 3 and C or time series. We show that the CaCO 3 events are caused by changes in CaCO 3 production by plankton, not by dissolution. We also show that these CaCO 3 events occur ...