- Email: [email protected]
Causes of early Holocene desertification in arid central Asia
Abstracts / Quaternary International 279-280 (2012) 121–232
from other regions around the world. This coincided in timing with the modeling results that the closure of the Central American Seaway (CAS) initiated strengthening of Atlantic meridional overturning circulation between 4.8 and 4.0 Ma which led to both warming of the Northern Hemisphere (NH) and cooling of the Southern Hemisphere (SH). Cooling of the SH would induce a marked development of the Antarctic ice sheets at w4 Ma, pushing the Intertropical Convergence Zone (ITCZ) northward. This was superimposed on warming of the NH and brought more precipitation to the middle latitudes of the NH, resulting in increases in coarsegrained sediments in the Sikouzi section from the western CLP since 4.2 Ma. Notably, absence of coarse-grained sedimentation in the Sikouzi section during 3.0-2.1 Ma and the gradual decrease in coarse-grained peaks since 2.1 Ma reflected by the Sikouzi grain-size record probably resulted from stepwise increase in the NH ice volume pushing the ITCZ southward. On the other hand, development of the Antarctic ice sheets would induce global cooling and enhancement of physical weathering, initiating increases in sedimentation rates as well as increases in grain size from Lake Baikal to the CLP to the SCS. Therefore the closure of the CAS during 4.8-4.0 Ma and its influence on ocean heat transport was possibly the major forcing factor for global cooling since 4 Ma. A persistent and steady cooling during 4-3 Ma probably made a significant contribution to the establishment of the NH ice sheets at 2.75 Ma ago. ORIGIN OF DOLOMITE IN LAKE BAYANCHAGAN, INNER MONGOLIA AND ITS PALAEOCLIMATIC IMPLICATIONS Wenying Jiang. Institute of Geology and Geophysics, Chinese Acade, China E-mail address: [email protected]
In this study, X-ray diffraction, scanning electron microscopy (SEM), measurements of carbonate content and d18O of authigenic carbonate were conducted for lake sediment from Bayanchagan, Inner Mongolia, for the last 12400 cal. aB.P. Results show that carbonate content is generally high (up to 55%) in the lake sediment. Calcite predominates in the carbonate fraction between 12,400 cal. aB.P. and 6000 cal. aB.P., and dolomite occurs after 6000 cal. aB.P. The calcite fraction consists of small (1w5 mm long), flaky and lenticular idiomorphic crystals. Dolomite occurs as a knobbly coating (<1 mm) on the surface of feldspar. The morphological features of calcite and dolomite indicate rapid carbonate precipitation. The dolomite grains are identical in shape and size to those with microbial origin reported in other regions, suggesting that microbial activities may play a key role in dolomite formation at Lake Bayanchagan. The presence of dolomite around 6000 cal. aB.P. provides depositional evidence for lake salinization, indicating increased aridity since the mid-Holocene. This mineralogical change is consistent with oxygen isotopic record of carbonate and pollen data. CAUSES OF EARLY HOLOCENE DESERTIFICATION IN ARID CENTRAL ASIA Liya Jin. Institute of Geosciences, University of Kiel, Germany E-mail address: [email protected]
Paleoclimate records of effective moisture show a dry (low effective moisture) period in mid-latitude arid/semi-arid central Asia during the early Holocene (11,000-8,000 years ago) relative to the middle and late Holocene, in contrast to evidence for greater-than-present precipitation at the same time in the south and east Asian monsoonal areas. To investigate the spatial differences in climate response over mid-latitude central Asia and monsoonal Asia we conducted a series of simulations with the NCAR CCSM3.0 coupled climate model for the early, middle and late Holocene. The simulations test the climatic impact of all important forcings for the early Holocene, including changes in orbital parameters, the presence of the remnant Laurentide ice sheet and deglacial freshening of the North Atlantic. Model results clearly show the early Holocene patterns indicated by proxy records, including both the decreased effective moisture in arid central Asia, which occurs primarily during the winter months, and the increase in summer monsoon precipitation in south and east Asia. The model results suggest that dry conditions in the early Holocene in central Asia are closely related to decreased water vapor advection due to reduced westerly wind speed and less evaporation upstream from the Mediterranean, Black, and
223
Caspian Seas in boreal winter.As an extra forcing to the early Holocene climate system, the Laurentide ice sheet and meltwater fluxes have a substantial cooling effect over high latitudes, especially just over and downstream of the ice sheets, but contribute only to a small degree to the early Holocene aridity in central Asia. Instead, most of the effective moisture signal can be explained by orbital forcing decreasing the early Holocene latitudinal temperature gradient and wintertime surface temperature. We find little evidence for regional subsidence related to a stronger summer Asian monsoon in forcing early Holocene aridity in central Asia, as has been previously hypothesized. THE EARLY FARMERS AND THEIR EFFECTS ON THE LANDSCAPE IN SHANDONG PENINSULA, EASTERN CHINA Gui-Yun Jin. Shandong University, China E-mail address: [email protected]
In the studied area, the first Neolithic culture is Houli Culture and the microlithic archaeological remains which have not yet been well dated nor studied should be earlier than the Houli Culture. Even though it is still unknown about the origin of the Houli people, the arrival of them actually changed the landscape of the Shandong peninsula, especially the area around the Tai-Yi Mountain, where most Houli Culture sites located. By the present archaeological evidence especially bio-archaeological evidence, the landscape change should be caused by the following human activities: (1) settlement building changed the landscape where they live; (2) initial and small scale cultivation changed landscape around the village; (3) the above-mentioned activities altered the vegetation near the settlement; (4) hunting and intensive collecting made the change of the ecological situation. By the all human activities above, the landscape had been reshaped much intensive during the Houli Culture in Shandong Peninsula, east China. According to the new archaeobotanic and zooarchaeological data in China, Shandong Peninsula become more and more important for the study of the transition to agro-pastoralism. SMALL MAMMALS FROM THE LATE PLEISTOCENE HUMAN OCCUPATION SITE OF TANGZIGOU, WESTERN YUNNAN, CHINA: PALEOENVIRONMENTAL AND ARCHAEOLOGICAL PERSPECTIVES Jennie Jin. University of Hawaii at Manoa, United States E-mail address: [email protected]
The Late Pleistocene human occupation site of Tangzigou in western Yunnan Province has yielded numerous mammalian fossils, including craniodental remains of small mammals that could be identified to at least the family level. The Tangzigou small mammal assemblage is composed mostly (96%) of rodents, with larger murids constituting the largest fraction, followed by rhizomyids, sciurids, and hystricids. The Tangzigou small mammals all represent extant species, of which the vast majority are known to be arboreal or forest-floor dwellers. The assemblage is also important because it appears to represent an accumulation of animals that had been trapped or snared by humans, and not one that was formed as the result of a commensal association. The overall picture provided by the fossil and tool assemblages at Tangzigou is one of a forest or forest-edge environment in which humans captured and consumed a wide variety of animals, including numerous small mammals. AN EXAMPLE OF DENDROCHEMISTRY ANALYSES USING ITRAX AND ITS COMPARISON WITH OBSERVED CLIMATE RECORDS Jae Hwa Jin. Korea Institut of Geoscience and Mineral Resources, Korea E-mail address: [email protected]
Using ITRAX, analyses of dendrochemistry have been made over more than one-hundred-year treerings of Pinus densiflora obtained from the mideastern area of Korea. A significant change in dendrochemistry occurs at the boundary between Heartwood and Sapwood - high content in Sapwood. Among the elements, Ca shows the best distinction in content between spring wood and autum wood. The dendrochemistry are not matched peak by peak with the observed climate record. A large positive
from other regions around the world. This coincided in timing with the modeling results that the closure of the Central American Seaway (CAS) initiated strengthening of Atlantic meridional overturning circulation between 4.8 and 4.0 Ma which led to both warming of the Northern Hemisphere (NH) and cooling of the Southern Hemisphere (SH). Cooling of the SH would induce a marked development of the Antarctic ice sheets at w4 Ma, pushing the Intertropical Convergence Zone (ITCZ) northward. This was superimposed on warming of the NH and brought more precipitation to the middle latitudes of the NH, resulting in increases in coarsegrained sediments in the Sikouzi section from the western CLP since 4.2 Ma. Notably, absence of coarse-grained sedimentation in the Sikouzi section during 3.0-2.1 Ma and the gradual decrease in coarse-grained peaks since 2.1 Ma reflected by the Sikouzi grain-size record probably resulted from stepwise increase in the NH ice volume pushing the ITCZ southward. On the other hand, development of the Antarctic ice sheets would induce global cooling and enhancement of physical weathering, initiating increases in sedimentation rates as well as increases in grain size from Lake Baikal to the CLP to the SCS. Therefore the closure of the CAS during 4.8-4.0 Ma and its influence on ocean heat transport was possibly the major forcing factor for global cooling since 4 Ma. A persistent and steady cooling during 4-3 Ma probably made a significant contribution to the establishment of the NH ice sheets at 2.75 Ma ago. ORIGIN OF DOLOMITE IN LAKE BAYANCHAGAN, INNER MONGOLIA AND ITS PALAEOCLIMATIC IMPLICATIONS Wenying Jiang. Institute of Geology and Geophysics, Chinese Acade, China E-mail address: [email protected]
In this study, X-ray diffraction, scanning electron microscopy (SEM), measurements of carbonate content and d18O of authigenic carbonate were conducted for lake sediment from Bayanchagan, Inner Mongolia, for the last 12400 cal. aB.P. Results show that carbonate content is generally high (up to 55%) in the lake sediment. Calcite predominates in the carbonate fraction between 12,400 cal. aB.P. and 6000 cal. aB.P., and dolomite occurs after 6000 cal. aB.P. The calcite fraction consists of small (1w5 mm long), flaky and lenticular idiomorphic crystals. Dolomite occurs as a knobbly coating (<1 mm) on the surface of feldspar. The morphological features of calcite and dolomite indicate rapid carbonate precipitation. The dolomite grains are identical in shape and size to those with microbial origin reported in other regions, suggesting that microbial activities may play a key role in dolomite formation at Lake Bayanchagan. The presence of dolomite around 6000 cal. aB.P. provides depositional evidence for lake salinization, indicating increased aridity since the mid-Holocene. This mineralogical change is consistent with oxygen isotopic record of carbonate and pollen data. CAUSES OF EARLY HOLOCENE DESERTIFICATION IN ARID CENTRAL ASIA Liya Jin. Institute of Geosciences, University of Kiel, Germany E-mail address: [email protected]
Paleoclimate records of effective moisture show a dry (low effective moisture) period in mid-latitude arid/semi-arid central Asia during the early Holocene (11,000-8,000 years ago) relative to the middle and late Holocene, in contrast to evidence for greater-than-present precipitation at the same time in the south and east Asian monsoonal areas. To investigate the spatial differences in climate response over mid-latitude central Asia and monsoonal Asia we conducted a series of simulations with the NCAR CCSM3.0 coupled climate model for the early, middle and late Holocene. The simulations test the climatic impact of all important forcings for the early Holocene, including changes in orbital parameters, the presence of the remnant Laurentide ice sheet and deglacial freshening of the North Atlantic. Model results clearly show the early Holocene patterns indicated by proxy records, including both the decreased effective moisture in arid central Asia, which occurs primarily during the winter months, and the increase in summer monsoon precipitation in south and east Asia. The model results suggest that dry conditions in the early Holocene in central Asia are closely related to decreased water vapor advection due to reduced westerly wind speed and less evaporation upstream from the Mediterranean, Black, and
223
Caspian Seas in boreal winter.As an extra forcing to the early Holocene climate system, the Laurentide ice sheet and meltwater fluxes have a substantial cooling effect over high latitudes, especially just over and downstream of the ice sheets, but contribute only to a small degree to the early Holocene aridity in central Asia. Instead, most of the effective moisture signal can be explained by orbital forcing decreasing the early Holocene latitudinal temperature gradient and wintertime surface temperature. We find little evidence for regional subsidence related to a stronger summer Asian monsoon in forcing early Holocene aridity in central Asia, as has been previously hypothesized. THE EARLY FARMERS AND THEIR EFFECTS ON THE LANDSCAPE IN SHANDONG PENINSULA, EASTERN CHINA Gui-Yun Jin. Shandong University, China E-mail address: [email protected]
In the studied area, the first Neolithic culture is Houli Culture and the microlithic archaeological remains which have not yet been well dated nor studied should be earlier than the Houli Culture. Even though it is still unknown about the origin of the Houli people, the arrival of them actually changed the landscape of the Shandong peninsula, especially the area around the Tai-Yi Mountain, where most Houli Culture sites located. By the present archaeological evidence especially bio-archaeological evidence, the landscape change should be caused by the following human activities: (1) settlement building changed the landscape where they live; (2) initial and small scale cultivation changed landscape around the village; (3) the above-mentioned activities altered the vegetation near the settlement; (4) hunting and intensive collecting made the change of the ecological situation. By the all human activities above, the landscape had been reshaped much intensive during the Houli Culture in Shandong Peninsula, east China. According to the new archaeobotanic and zooarchaeological data in China, Shandong Peninsula become more and more important for the study of the transition to agro-pastoralism. SMALL MAMMALS FROM THE LATE PLEISTOCENE HUMAN OCCUPATION SITE OF TANGZIGOU, WESTERN YUNNAN, CHINA: PALEOENVIRONMENTAL AND ARCHAEOLOGICAL PERSPECTIVES Jennie Jin. University of Hawaii at Manoa, United States E-mail address: [email protected]
The Late Pleistocene human occupation site of Tangzigou in western Yunnan Province has yielded numerous mammalian fossils, including craniodental remains of small mammals that could be identified to at least the family level. The Tangzigou small mammal assemblage is composed mostly (96%) of rodents, with larger murids constituting the largest fraction, followed by rhizomyids, sciurids, and hystricids. The Tangzigou small mammals all represent extant species, of which the vast majority are known to be arboreal or forest-floor dwellers. The assemblage is also important because it appears to represent an accumulation of animals that had been trapped or snared by humans, and not one that was formed as the result of a commensal association. The overall picture provided by the fossil and tool assemblages at Tangzigou is one of a forest or forest-edge environment in which humans captured and consumed a wide variety of animals, including numerous small mammals. AN EXAMPLE OF DENDROCHEMISTRY ANALYSES USING ITRAX AND ITS COMPARISON WITH OBSERVED CLIMATE RECORDS Jae Hwa Jin. Korea Institut of Geoscience and Mineral Resources, Korea E-mail address: [email protected]
Using ITRAX, analyses of dendrochemistry have been made over more than one-hundred-year treerings of Pinus densiflora obtained from the mideastern area of Korea. A significant change in dendrochemistry occurs at the boundary between Heartwood and Sapwood - high content in Sapwood. Among the elements, Ca shows the best distinction in content between spring wood and autum wood. The dendrochemistry are not matched peak by peak with the observed climate record. A large positive