Quantitative morphologic analysis of shallowly buried, dendritic channel systems in the continental shelf off the abandoned Huanghe River （Yellow River） mouth has been made based on interpretation of high resolution...Quantitative morphologic analysis of shallowly buried, dendritic channel systems in the continental shelf off the abandoned Huanghe River （Yellow River） mouth has been made based on interpretation of high resolution seismic profiles, with the attempt to estimate the paleo-hydrologic parameters when the incised-channels formed, then assess the paleoenvironment. The results indicate that the buried channel systems were formed about 44 cal ka BP when the shelf was subaerially exposed and subsequently drowned and filled during the Holocene transgression with the sea level rise continuously. The study area has experienced the processes from fluvial and estuarine to fully marine.展开更多
Integrated studies of vertical sedimentary sequences, grain sizes, and benthic foraminifera and ostracoda, in combination with AMS 14C dating, and 210pb and 137Cs analysis were carried out in three vibracores taken fr...Integrated studies of vertical sedimentary sequences, grain sizes, and benthic foraminifera and ostracoda, in combination with AMS 14C dating, and 210pb and 137Cs analysis were carried out in three vibracores taken from the area of relict deposits on the western South Yellow Sea. The relict sands, which are about 0.4 m thick, overlie on the Early Holocene coastal marsh or tidal fiat deposits with an evident erosional interface in between. The middle and upper parts or sometimes the whole of the relict sands have been reworked under the modern dynamic environment. The sedimentation rate varies between 0.204）.30 cmyear-l. The relict sands show a bimodal grain-size distribution pattern in frequency curves, with a sharp peak in the coarse fraction between 3（I） and 4（I） and a secondary peak in the fine fraction of about 7（I）. Of the benthic foraminiferal and ostracod assemblages, the reworked relict sands are characterized by the mixing of the nearshore euryhaline shallow-water species and deeper water species. The erosional interface at the bottom of the relict sands is considered as a regional ravinement surface formed during the transgression in the Early Holocene due to shoreface retreating landwards. The relict sands were accumulated on the ravinement surface during the transgression in the deglaciation period as lag deposits after winnowing and reworking by marine dynamic processes. And the secondary peak of fine fraction in the frequency curve for the relict sands suggests the input of fine-grained sediments during the reworking process. As the conclusion, the relict sands in the study area are interpreted as a type of reworked relict sediments.展开更多
基金The National Natural Science Foundation of China under grant No. 40876034the National Basic Research Program under grant No. 1212010611401
文摘Quantitative morphologic analysis of shallowly buried, dendritic channel systems in the continental shelf off the abandoned Huanghe River （Yellow River） mouth has been made based on interpretation of high resolution seismic profiles, with the attempt to estimate the paleo-hydrologic parameters when the incised-channels formed, then assess the paleoenvironment. The results indicate that the buried channel systems were formed about 44 cal ka BP when the shelf was subaerially exposed and subsequently drowned and filled during the Holocene transgression with the sea level rise continuously. The study area has experienced the processes from fluvial and estuarine to fully marine.
基金funded by the National Natural Science Foundation of China (Grant Nos.41330964 and 40876034)the China Geological Survey (Grant No.1212010611401)
文摘Integrated studies of vertical sedimentary sequences, grain sizes, and benthic foraminifera and ostracoda, in combination with AMS 14C dating, and 210pb and 137Cs analysis were carried out in three vibracores taken from the area of relict deposits on the western South Yellow Sea. The relict sands, which are about 0.4 m thick, overlie on the Early Holocene coastal marsh or tidal fiat deposits with an evident erosional interface in between. The middle and upper parts or sometimes the whole of the relict sands have been reworked under the modern dynamic environment. The sedimentation rate varies between 0.204）.30 cmyear-l. The relict sands show a bimodal grain-size distribution pattern in frequency curves, with a sharp peak in the coarse fraction between 3（I） and 4（I） and a secondary peak in the fine fraction of about 7（I）. Of the benthic foraminiferal and ostracod assemblages, the reworked relict sands are characterized by the mixing of the nearshore euryhaline shallow-water species and deeper water species. The erosional interface at the bottom of the relict sands is considered as a regional ravinement surface formed during the transgression in the Early Holocene due to shoreface retreating landwards. The relict sands were accumulated on the ravinement surface during the transgression in the deglaciation period as lag deposits after winnowing and reworking by marine dynamic processes. And the secondary peak of fine fraction in the frequency curve for the relict sands suggests the input of fine-grained sediments during the reworking process. As the conclusion, the relict sands in the study area are interpreted as a type of reworked relict sediments.
