- Email: [email protected]
Human Population Decline across Parts of the Northern Hemisphere during the Younger Dryas Cooling Period
18
Abstracts / Quaternary International 279-280 (2012) 9–120
HOLOCENE CLIMATE AND ENVIRONMENTAL HISTORY OF VICTORIA BASIN: EVIDENCE FROM GEOCHEMICAL PROXIES
LAKE
Morgan Andama. Mbarara University of Science and Technology, Uganda E-mail address: [email protected]
Geochemical analysis of sedimentary records from selected sites of Lake Victoria basin together with meteorological data has provided evidence of climate variability and environmental changes in Lake Victoria basin for the last ca. 10,000 years. Results show that Lake Victoria was relatively more anoxic before the Late Holocene from ca. 11942 - 11506 yr. BP possibly due to natural climate variability. TOC/TS values indicate that Lake Victoria waters were less saline from ca 12033 to 10732 yr. BP, but the salinity increased during the mid- to late-Holocene from ca. 4186 to 1101 yr. BP. However, Lake Victoria waters were more anoxic from ca. 370 yr. BP to present. Increased productivity was experienced at Napoleon Gulf (Jinja) site from ca. 370 yr. BP to present. High catchment destruction was recorded in the last ca 190 yr. BP to present, being pronounced at the inlet of river Kagera. From ca. 1950 AD to present, evidence of catchment destruction at the inlet of river Kagera drastically decreased, possibility due to the control management measures set by the government, as this correlated with the formation of Kagera Basin Organisation (KBO, 1977). The anoxic conditions most likely resulted from the interplay of both eutrophication from input of nitrates and other natural causes. Increasing TOC/TS values, which reflect decreasing salinity correlated with increasing rainfall and river discharge in Lake Victoria basin from beyond 1950 AD to present. The reduced salinity can therefore be attributed to dilution by increased rainfall pattern from ca. 10732- 10688 yr. BP and ca. 1101 yr. BP to present and increased salinity due to decreased rainfall from ca. 12033 10732 yr. BP. and ca. 4186 - 1101 yr. BP. HIGH THROUGHPUT BARCODING OF DNA FROM SURFACE SOILS REFLECTS VERTEBRATE BIODIVERSITY Kenneth Andersen. Copenhagen University, Denmark E-mail address: [email protected]
DNA originating from both vertebrates and plants can be obtained directly from sediments and have been used for reconstructing both contemporary and past ecosystems. The extent to which such “dirt” DNA reflects above ground diversity, however, remains contentious. Recently, a comparative study on above ground plant biomass and soil DNA shows that “dirt” plant chloroplast DNA (cpDNA) closely reflects both structural and functional diversity. However, compared to plants, animals are mobile and often have much lower densities possibly influencing DNA results. Here, we couple mitochondrial DNA (mtDNA) barcoding of “dirt DNA” with second generation high throughput sequencing to explore vertebrate diversity in soils of safari parks, zoological gardens, and farms where the animal history is well established. We find that DNA from surface soil reflects overall taxonomic richness and relative biomass of individual species. Most reliable results are obtained when including a spatial sampling scale, while relative amounts of soil processed per site is of less importance. Intriguingly, species represented by low relative biomass, or which had recently been introduced, were not detected, and in some cases animal behaviour was shown to influence DNA deposition rates. DNA PCR amplification was successful in the full pH range of the investigated soils (6.20.2 to 8.30.2), but inhibition in extracts from soil of high organic content was detected. DNA movement (leaching) through strata was detected in some cases and is dependent of soil texture and composition. The results demonstrate that overall vertebrate diversity is reflected in surface soil and that the approach holds great potential for quick ecological biodiversity surveying.
which were formed by ice streams that occupied glacial troughs during the LGM. However, with the exception of grounding zone wedges, few studies have yielded high-resolution sea floor images that show geomorphic features formed by retreating ice streams. For example, deep-tow sidescan sonar records from Ross Sea show a range of recessional features, mostly 1-3 meters high, that overprint mega-scale glacial lineations. These features were not imaged in swath bathymetry records. During the 2010 austral summer, the Swedish ice breaker Oden was used to conduct an extensive survey in the sparsely studied central trough in Pine Island Bay using the latest generation multibeam technology. The bedforms imaged in Pine Island Bay are similar to small-scale recessional features previously imaged in Ross Sea using deep-tow side-scan sonar. These include fishbone moraines and corrugated iceberg furrows, which we argue were produced daily through tidally-influenced motion of a disintegrating ice shelf. During this event a 65 km long stretch of the trough was cleared of floating ice in about 1.5 years. The break-up occurred w12,000 cal ka BP and was likely a response to rapid sea-level rise at that time. Acquisition of more high-resolution swath bathymetry data should greatly increase our understanding of ice stream interaction with the seafloor and those factors that have influenced ice stream behavior during retreat. Future work should focus on the rugged inner shelf, were subglacial meltwater is believed to have contributed to ice stream instability. HUMAN POPULATION DECLINE ACROSS PARTS OF THE NORTHERN HEMISPHERE DURING THE YOUNGER DRYAS COOLING PERIOD David G. Anderson. The Univ. of Tennessee, United States E-mail address: [email protected]
There is an ongoing debate about a possible human population decline or contraction at the onset of the Younger Dryas (YD) at 12.9 ka. We used three methods to test whether YD climate change affected human population levels. Frequency Analyses: This method employed lithic projectile point data from the Paleoindian Database of the Americas (PIDBA, http:// pidba.utk.edu). We tallied diagnostic projectile points used by North American Paleoindian cultures, such as Clovis, that existed prior to about 12.9 ka, and obtained point totals that were larger than those of immediately post-Clovis cultures. For the SE U.S., the ratio of Clovis points (n¼1993) to post-Clovis points (n¼947) reveals a point decline of 52%. For the Great Plains, a comparison of Clovis and fluted points (n¼4020) to Folsom points (n¼2527) shows a point decline of 37%, suggesting a population contraction of similar magnitude. Quarry Usage: Eleven major Clovis-age lithic quarry sites in the Southeastern U.S. exhibit either limited usage or total abandonment just after the YD onset, only to resume normal usage hundreds of years later. Those usage patterns imply a severe population decline or reorganization around 12.9 ka. Summed Probabilities: This method involved calibrating relevant 14C dates from across the Northern Hemisphere and combining the probabilities, after which major peaks and troughs in the trends were assumed to reflect changes in human demographics. We found an abrupt, statistically significant decline at 12.9 ka, followed by a rebound 200 to 900 years later. The overall decline was more than 50%, similar in magnitude to the decline in Clovis-Folsom point ratios. The coeval YD declines in projectile points, quarry usage, and 14C dates appear linked to significant changes in climate and biota. While the causes of the YD remain controversial, evidence suggests that human population declines occurred nearly simultaneously across the Northern Hemisphere around 12.9 ka. HOLOCENE CLIMATE RECORDS FROM LAKE CALCITE-d18O IN THE NORTH AMERICAN CORDILLERA: INSIGHTS INTO PACIFIC CLIMATE PATTERNS Lesleigh Anderson. U.S. Geological Survey, United States
GEOMORPHIC EXPRESSION OF COLLAPSING ICE STREAMS REVEALED BY LATEST GENERATION SWATH BATHYMETRY IMAGES John Anderson. Rice University, United States E-mail address: [email protected]
There is now a substantial swath bathymetry data set from Antarctica that reveals subglacial bedforms, in particular mega-scale glacial lineations,
E-mail address: [email protected]
North Pacific climate is known to have varied on decade-to-century time scales during the Holocene, but spatial patterns are poorly defined. Presented here are sediment-carbonate oxygen isotope (d18O) records with decade-to-century resolution from lakes located in the St. Elias Mountains of the Yukon Territory (Jellybean Lake) and the central Rocky Mountains of Colorado (Bison Lake). The records individually reflect their respective
Abstracts / Quaternary International 279-280 (2012) 9–120
HOLOCENE CLIMATE AND ENVIRONMENTAL HISTORY OF VICTORIA BASIN: EVIDENCE FROM GEOCHEMICAL PROXIES
LAKE
Morgan Andama. Mbarara University of Science and Technology, Uganda E-mail address: [email protected]
Geochemical analysis of sedimentary records from selected sites of Lake Victoria basin together with meteorological data has provided evidence of climate variability and environmental changes in Lake Victoria basin for the last ca. 10,000 years. Results show that Lake Victoria was relatively more anoxic before the Late Holocene from ca. 11942 - 11506 yr. BP possibly due to natural climate variability. TOC/TS values indicate that Lake Victoria waters were less saline from ca 12033 to 10732 yr. BP, but the salinity increased during the mid- to late-Holocene from ca. 4186 to 1101 yr. BP. However, Lake Victoria waters were more anoxic from ca. 370 yr. BP to present. Increased productivity was experienced at Napoleon Gulf (Jinja) site from ca. 370 yr. BP to present. High catchment destruction was recorded in the last ca 190 yr. BP to present, being pronounced at the inlet of river Kagera. From ca. 1950 AD to present, evidence of catchment destruction at the inlet of river Kagera drastically decreased, possibility due to the control management measures set by the government, as this correlated with the formation of Kagera Basin Organisation (KBO, 1977). The anoxic conditions most likely resulted from the interplay of both eutrophication from input of nitrates and other natural causes. Increasing TOC/TS values, which reflect decreasing salinity correlated with increasing rainfall and river discharge in Lake Victoria basin from beyond 1950 AD to present. The reduced salinity can therefore be attributed to dilution by increased rainfall pattern from ca. 10732- 10688 yr. BP and ca. 1101 yr. BP to present and increased salinity due to decreased rainfall from ca. 12033 10732 yr. BP. and ca. 4186 - 1101 yr. BP. HIGH THROUGHPUT BARCODING OF DNA FROM SURFACE SOILS REFLECTS VERTEBRATE BIODIVERSITY Kenneth Andersen. Copenhagen University, Denmark E-mail address: [email protected]
DNA originating from both vertebrates and plants can be obtained directly from sediments and have been used for reconstructing both contemporary and past ecosystems. The extent to which such “dirt” DNA reflects above ground diversity, however, remains contentious. Recently, a comparative study on above ground plant biomass and soil DNA shows that “dirt” plant chloroplast DNA (cpDNA) closely reflects both structural and functional diversity. However, compared to plants, animals are mobile and often have much lower densities possibly influencing DNA results. Here, we couple mitochondrial DNA (mtDNA) barcoding of “dirt DNA” with second generation high throughput sequencing to explore vertebrate diversity in soils of safari parks, zoological gardens, and farms where the animal history is well established. We find that DNA from surface soil reflects overall taxonomic richness and relative biomass of individual species. Most reliable results are obtained when including a spatial sampling scale, while relative amounts of soil processed per site is of less importance. Intriguingly, species represented by low relative biomass, or which had recently been introduced, were not detected, and in some cases animal behaviour was shown to influence DNA deposition rates. DNA PCR amplification was successful in the full pH range of the investigated soils (6.20.2 to 8.30.2), but inhibition in extracts from soil of high organic content was detected. DNA movement (leaching) through strata was detected in some cases and is dependent of soil texture and composition. The results demonstrate that overall vertebrate diversity is reflected in surface soil and that the approach holds great potential for quick ecological biodiversity surveying.
which were formed by ice streams that occupied glacial troughs during the LGM. However, with the exception of grounding zone wedges, few studies have yielded high-resolution sea floor images that show geomorphic features formed by retreating ice streams. For example, deep-tow sidescan sonar records from Ross Sea show a range of recessional features, mostly 1-3 meters high, that overprint mega-scale glacial lineations. These features were not imaged in swath bathymetry records. During the 2010 austral summer, the Swedish ice breaker Oden was used to conduct an extensive survey in the sparsely studied central trough in Pine Island Bay using the latest generation multibeam technology. The bedforms imaged in Pine Island Bay are similar to small-scale recessional features previously imaged in Ross Sea using deep-tow side-scan sonar. These include fishbone moraines and corrugated iceberg furrows, which we argue were produced daily through tidally-influenced motion of a disintegrating ice shelf. During this event a 65 km long stretch of the trough was cleared of floating ice in about 1.5 years. The break-up occurred w12,000 cal ka BP and was likely a response to rapid sea-level rise at that time. Acquisition of more high-resolution swath bathymetry data should greatly increase our understanding of ice stream interaction with the seafloor and those factors that have influenced ice stream behavior during retreat. Future work should focus on the rugged inner shelf, were subglacial meltwater is believed to have contributed to ice stream instability. HUMAN POPULATION DECLINE ACROSS PARTS OF THE NORTHERN HEMISPHERE DURING THE YOUNGER DRYAS COOLING PERIOD David G. Anderson. The Univ. of Tennessee, United States E-mail address: [email protected]
There is an ongoing debate about a possible human population decline or contraction at the onset of the Younger Dryas (YD) at 12.9 ka. We used three methods to test whether YD climate change affected human population levels. Frequency Analyses: This method employed lithic projectile point data from the Paleoindian Database of the Americas (PIDBA, http:// pidba.utk.edu). We tallied diagnostic projectile points used by North American Paleoindian cultures, such as Clovis, that existed prior to about 12.9 ka, and obtained point totals that were larger than those of immediately post-Clovis cultures. For the SE U.S., the ratio of Clovis points (n¼1993) to post-Clovis points (n¼947) reveals a point decline of 52%. For the Great Plains, a comparison of Clovis and fluted points (n¼4020) to Folsom points (n¼2527) shows a point decline of 37%, suggesting a population contraction of similar magnitude. Quarry Usage: Eleven major Clovis-age lithic quarry sites in the Southeastern U.S. exhibit either limited usage or total abandonment just after the YD onset, only to resume normal usage hundreds of years later. Those usage patterns imply a severe population decline or reorganization around 12.9 ka. Summed Probabilities: This method involved calibrating relevant 14C dates from across the Northern Hemisphere and combining the probabilities, after which major peaks and troughs in the trends were assumed to reflect changes in human demographics. We found an abrupt, statistically significant decline at 12.9 ka, followed by a rebound 200 to 900 years later. The overall decline was more than 50%, similar in magnitude to the decline in Clovis-Folsom point ratios. The coeval YD declines in projectile points, quarry usage, and 14C dates appear linked to significant changes in climate and biota. While the causes of the YD remain controversial, evidence suggests that human population declines occurred nearly simultaneously across the Northern Hemisphere around 12.9 ka. HOLOCENE CLIMATE RECORDS FROM LAKE CALCITE-d18O IN THE NORTH AMERICAN CORDILLERA: INSIGHTS INTO PACIFIC CLIMATE PATTERNS Lesleigh Anderson. U.S. Geological Survey, United States
GEOMORPHIC EXPRESSION OF COLLAPSING ICE STREAMS REVEALED BY LATEST GENERATION SWATH BATHYMETRY IMAGES John Anderson. Rice University, United States E-mail address: [email protected]
There is now a substantial swath bathymetry data set from Antarctica that reveals subglacial bedforms, in particular mega-scale glacial lineations,
E-mail address: [email protected]
North Pacific climate is known to have varied on decade-to-century time scales during the Holocene, but spatial patterns are poorly defined. Presented here are sediment-carbonate oxygen isotope (d18O) records with decade-to-century resolution from lakes located in the St. Elias Mountains of the Yukon Territory (Jellybean Lake) and the central Rocky Mountains of Colorado (Bison Lake). The records individually reflect their respective