In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional fro...In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.展开更多
A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high...A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high-resolution paleoclimate record for eastern China during a time interval (from 54 000 to 19 000 aBP) of the last glaciation. The continuous record of oxygen-18 variations in the stalagmite, indicating a precipitation history of the East Asian monsoon, shows not only signals of the Heinrich events, but also the Dansgaard-Oeschger cycles which are first found in the last glacial climate record of the East Asian monsoon area. Although the stalagmite-based climatic signals match well with the GRIP ice core record, some differences between the two re-cords can be recognized: (1) The last glacial climate changes in eastern China exhibited a long-term remarkably cooling trend, superimposed on which were four successive Bond’s cycles illus-trated by the δ18O curve. This strong cooling tendency may be an effect of the strong summer mon-soon event during the MIS 3 over the Tibetan Plateau. (2) There exist some phase differences of 1000—2000 years between the cooling events in the stalagmite-based climate signal and the GRIP ice core record. Such differences should be further verified by calibrations of multiple dating meth-ods.展开更多
In north of Taiwan the East China Sea Shelf extends from the coastline of China's Mainland to the southern Okinawa Trough, showing a shelf-slope-basin bathymetric profile. Sea floor of the East China Sea Shelf is ...In north of Taiwan the East China Sea Shelf extends from the coastline of China's Mainland to the southern Okinawa Trough, showing a shelf-slope-basin bathymetric profile. Sea floor of the East China Sea Shelf is generally smooth and flat. It is wide (230 km) and relatively shallow with an average shelf-break depth of 120 m, reflecting the effect of Quaternary glaciation about 15000 years ago. The Pliocene-Quaternary East China Sea Shelf is underlain by thin sequences of about 1000 m thick shallow marine sediments mainly derived from China, forming an eastward dipping sedimentary wedge due to regional tilting and subsidence and representing the youngest part of the Cenozoic rift margin in southeastern China. The Taiwan Strait Shelf has two phases in development: one is the early phase of the Paleo-cene-Miocene rift margin and the other is the late stage of the Pliocene-Quaternary foreland sedi-mentation. It is a foreland shelf and its present morphology results from the combined effects of tectonic subsidence and sedimentation overprinting that of the Late Pleistocene glaciation about 15000 years ago.Southeast of the Taiwan Strait Shelf lies the very narrow Kaoping Shelf along the southwest-ern Taiwan coast. The island shelf is a short, narrow and shallow shelf (100 km long, 20 km wide and 80 m deep). Progradation of Quaternary orogenic sediments from the Taiwan orogen forms the present island shelf off southwest Taiwan. The shelf represents the early stage of foreland basin sedimentation.The transition from a passive margin shelf (East China Sea Shelf), a foreland shelf (Taiwan Strait Shelf) to an island shelf (Kaoping Shelf) along the strike of the fold-and-thrust belt of Taiwan mainly reflects the oblique collision between the Luzon Arc and the Chinese margin from Pliocene to the present. The accompanying uplift of Taiwan orogen, foreland-basin sedimentation, and sea level changes contribute to the formation of these three different shelves adjacent to Taiwan.展开更多
基金supported by the Key Project of the National Natural Science Foundation of China (No. 50534040)the Project of the National Natural Science Foundation of China (No. 40471021)
文摘In order to study the evolution of the freezing fringe and final lenses of frost susceptible soils and advance the understanding of frost heave and mechanism of frost heave control, we used an open one-dimensional frost heave test system of infrared radiation technology, instead of a traditional thermistor method. Temperatures of the freezing fringe and segregated ice were measured in a non-contact mode. The results show that accurate and precise temperatures of ice segregation can be obtained by infrared thermal imaging systems. A self-developed inversion program inverted the temperature field of frozen soils. Based on our analysis of temperature variation in segregated ice and our study of the relationship between temperature and rate of ice segregation in cooling and warming processes during intermittent freezing, the mechanism of decreasing frost heave of frozen soils by controlling the growth of final lenses with an intermittent freezing mode, can be explained properly.
基金the National Natural Science Foundation of China (Grant No.49972055). We thank Dr. Hai Cheng at Isotope Laboratory of Geology and Geophysics Department, Minnesota University, USA for his measurement of TIMS-U series dating.
文摘A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high-resolution paleoclimate record for eastern China during a time interval (from 54 000 to 19 000 aBP) of the last glaciation. The continuous record of oxygen-18 variations in the stalagmite, indicating a precipitation history of the East Asian monsoon, shows not only signals of the Heinrich events, but also the Dansgaard-Oeschger cycles which are first found in the last glacial climate record of the East Asian monsoon area. Although the stalagmite-based climatic signals match well with the GRIP ice core record, some differences between the two re-cords can be recognized: (1) The last glacial climate changes in eastern China exhibited a long-term remarkably cooling trend, superimposed on which were four successive Bond’s cycles illus-trated by the δ18O curve. This strong cooling tendency may be an effect of the strong summer mon-soon event during the MIS 3 over the Tibetan Plateau. (2) There exist some phase differences of 1000—2000 years between the cooling events in the stalagmite-based climate signal and the GRIP ice core record. Such differences should be further verified by calibrations of multiple dating meth-ods.
基金J. C. Chen, Institute of Oceanography, NTU and F. W. Huang, Chinese Petroleum Company, Taiwan, critically reviewed the manuscript of this paper. Critical reviews and constructive comments of professors F. N. Peng, Second Institute of Oceanography, SOA, H
文摘In north of Taiwan the East China Sea Shelf extends from the coastline of China's Mainland to the southern Okinawa Trough, showing a shelf-slope-basin bathymetric profile. Sea floor of the East China Sea Shelf is generally smooth and flat. It is wide (230 km) and relatively shallow with an average shelf-break depth of 120 m, reflecting the effect of Quaternary glaciation about 15000 years ago. The Pliocene-Quaternary East China Sea Shelf is underlain by thin sequences of about 1000 m thick shallow marine sediments mainly derived from China, forming an eastward dipping sedimentary wedge due to regional tilting and subsidence and representing the youngest part of the Cenozoic rift margin in southeastern China. The Taiwan Strait Shelf has two phases in development: one is the early phase of the Paleo-cene-Miocene rift margin and the other is the late stage of the Pliocene-Quaternary foreland sedi-mentation. It is a foreland shelf and its present morphology results from the combined effects of tectonic subsidence and sedimentation overprinting that of the Late Pleistocene glaciation about 15000 years ago.Southeast of the Taiwan Strait Shelf lies the very narrow Kaoping Shelf along the southwest-ern Taiwan coast. The island shelf is a short, narrow and shallow shelf (100 km long, 20 km wide and 80 m deep). Progradation of Quaternary orogenic sediments from the Taiwan orogen forms the present island shelf off southwest Taiwan. The shelf represents the early stage of foreland basin sedimentation.The transition from a passive margin shelf (East China Sea Shelf), a foreland shelf (Taiwan Strait Shelf) to an island shelf (Kaoping Shelf) along the strike of the fold-and-thrust belt of Taiwan mainly reflects the oblique collision between the Luzon Arc and the Chinese margin from Pliocene to the present. The accompanying uplift of Taiwan orogen, foreland-basin sedimentation, and sea level changes contribute to the formation of these three different shelves adjacent to Taiwan.
