Depositional units preserved on coastal plains worldwide control lithologic distribution in the shallow subsurface that is critical to infrastructure design and construction, and are also an important repository of in...Depositional units preserved on coastal plains worldwide control lithologic distribution in the shallow subsurface that is critical to infrastructure design and construction, and are also an important repository of information about the large-scale climate change that has occurred during many Quaternary glacial-interglacial cycles, The lateral and vertical lithologic and stratigraphic complexity of these depositional units and their response to climatic and sea-level change are poorly understood, making it difficult to pre-dict lithologic distribution and to place historical and future climate and sea-level change within a nat-ural geologic context, Mapping Quaternary siliciclastic depositional units on low-relief coastal plains traditionally has been based on their expression in aerial photographs and low-resolution topographic maps, Accuracy and detail have been hindered by low relief and lack of exposure, High-resolution air- borne lidar surveys, along with surface and borehole geophysical measurements, are being used to iden-tify subtle lateral and vertical boundaries of lithologic units on the Texas Coastal Plain within Quaternary strata, Ground and borehole conductivity measurements discriminate sandy barrier island and fluvial and deltaic channel deposits from muddy floodplain, delta-plain, and estuarine deposits, Borehole conductiv- ity and natural gamma logs similarly distinguish distinct lithologic units in the subsurface and identify erosional unconformities that likely separate units deposited during different glacial-interglacial stages, High-resolution digital elevation models obtained from airborne lidar surveys reveal previously unrecog- nized topographic detail that aids identification of surface features such as sandy channels, clay-rich interchannel deposits, and accretionary features on Pleistocene barrier islands, An optimal approach to identify lithologic and stratigraphic distribution in low-relief coastal-plain environments employs ① an initial lidar survey to produce a detailed elevation model; ② selective surface sampling and geophysical measurements based on preliminary mapping derived from lidar data and aerial imagery; and ③ borehole sampling, logging, and analysis at key sites selected after lidar and surface measure- ments are complete,展开更多
Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic s...Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance （ESR）, 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event （320 kaBP）, Biwa- 1I event （260 kaBP）, Biwa- I event （180 kaBP, scarcity due to the disturbance of the iron dish）, Blake event （100 kaBP） and Laschamp event （20 kaBP, didn＇t grow due to the activities of the surface）, etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively ： Stage [ is the climate period of glacial epoch （200-400 kaBP）; stage 11 is the climate period of interglacial epoch （100-200 kaBP）; stage llI is the climate peri- od of periglacial epoch （10-100 kaBP）; stage IV is the climate period ofpostglacial epoch （0-10 kaBP）.展开更多
基金partly supported by the US Geological Survey (USGS) National Cooperative Geologic Mapping Program (G13AC00178)
文摘Depositional units preserved on coastal plains worldwide control lithologic distribution in the shallow subsurface that is critical to infrastructure design and construction, and are also an important repository of information about the large-scale climate change that has occurred during many Quaternary glacial-interglacial cycles, The lateral and vertical lithologic and stratigraphic complexity of these depositional units and their response to climatic and sea-level change are poorly understood, making it difficult to pre-dict lithologic distribution and to place historical and future climate and sea-level change within a nat-ural geologic context, Mapping Quaternary siliciclastic depositional units on low-relief coastal plains traditionally has been based on their expression in aerial photographs and low-resolution topographic maps, Accuracy and detail have been hindered by low relief and lack of exposure, High-resolution air- borne lidar surveys, along with surface and borehole geophysical measurements, are being used to iden-tify subtle lateral and vertical boundaries of lithologic units on the Texas Coastal Plain within Quaternary strata, Ground and borehole conductivity measurements discriminate sandy barrier island and fluvial and deltaic channel deposits from muddy floodplain, delta-plain, and estuarine deposits, Borehole conductiv- ity and natural gamma logs similarly distinguish distinct lithologic units in the subsurface and identify erosional unconformities that likely separate units deposited during different glacial-interglacial stages, High-resolution digital elevation models obtained from airborne lidar surveys reveal previously unrecog- nized topographic detail that aids identification of surface features such as sandy channels, clay-rich interchannel deposits, and accretionary features on Pleistocene barrier islands, An optimal approach to identify lithologic and stratigraphic distribution in low-relief coastal-plain environments employs ① an initial lidar survey to produce a detailed elevation model; ② selective surface sampling and geophysical measurements based on preliminary mapping derived from lidar data and aerial imagery; and ③ borehole sampling, logging, and analysis at key sites selected after lidar and surface measure- ments are complete,
基金Open Foundation for State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences(No.SKLLQG0701)Hunan Province Key Subject Construction Item(No.ZRDL0701)Open Foundation for State Key Laboratory of Continental Dynamics,Northwest University(No.DL2006001)
文摘Through the scientific investigation on Lushan for a long time, detailed studies have been carried out on the geologic stratum section of Late Quaternary in Dajiaochang. The series age data of complete stratigraphic section and full time formation since 400 kaBP were based on the results of the analyses using the dating methods with various instruments such as the ancient geomagnetism, electronics spin resonance （ESR）, 36C1 and lumines- cence dating, etc. Corresponding to these data, it identified the paleomagnetic polarity events including Biwa- III event （320 kaBP）, Biwa- 1I event （260 kaBP）, Biwa- I event （180 kaBP, scarcity due to the disturbance of the iron dish）, Blake event （100 kaBP） and Laschamp event （20 kaBP, didn＇t grow due to the activities of the surface）, etc. Combined with the sequence stratigraphy, layer type characteristics and its sediment environment, the strati- graphic can be divided into 4 stages of development respectively ： Stage [ is the climate period of glacial epoch （200-400 kaBP）; stage 11 is the climate period of interglacial epoch （100-200 kaBP）; stage llI is the climate peri- od of periglacial epoch （10-100 kaBP）; stage IV is the climate period ofpostglacial epoch （0-10 kaBP）.
