通过对榕江平原揭阳地区钻孔ZK01和ZK02硅藻记录的分析,结合沉积学特征和年代数据,重建榕江平原全新世以来的古环境演化。约10.4~8.5 ka B.P.,钻孔所在地尚未受到海水影响,发育河漫滩-淡水沼泽环境。8.5~5.5 ka B.P.海水入侵,形成潮间...通过对榕江平原揭阳地区钻孔ZK01和ZK02硅藻记录的分析,结合沉积学特征和年代数据,重建榕江平原全新世以来的古环境演化。约10.4~8.5 ka B.P.,钻孔所在地尚未受到海水影响,发育河漫滩-淡水沼泽环境。8.5~5.5 ka B.P.海水入侵,形成潮间带沼泽-潮滩相沉积。5.5~3.9 ka B.P.本区为河口湾环境,约5.5 ka B.P.海侵影响达到最大,硅藻总丰度和分异度达到最高值。3.9~3.7 ka B.P.发生一次短暂海退,硅藻总丰度明显下降,ZK01孔发育咸水沼泽相沉积,ZK02孔仍为河口湾相沉积。3.7~2.4 ka B.P.海平面再次上升至相对稳定,研究区持续发育河口湾环境,期间出现3次小规模的水深变化旋回。2.4 ka B.P以来海水退出,河流作用增强,研究区发育三角洲平原相沉积。展开更多
The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic- poor sediments. The geochemica...The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic- poor sediments. The geochemical characteristics of the Honggang member have been documented to determine the organic matter types and depositional environments in this paper. The organic matter of the black shales mainly consists of a mixture of land plant-derived and phytoplankton-derived organic matter. Total organic carbon content （TOC）-sulfur-iron （Fe） relationships suggest that the organicrich black shales were deposited under dysoxic-to-euxinic water conditions. The time that iron minerals remained in contact with H2S in anoxic waters possibly influenced the formation of syngenetic pyrite, and organic carbon controlled the formation of diagenetic pyrite. Organic-poor intervals usually show pyrite sulfur enrichment and higher degree of pyritization values relative to low organic carbon contents. This resulted from HS- diffusing downward from overlying organic-rich sediments and formed Fe sulfides through reactions with sufficient Fe. Trace elements generally exhibit low concentrations and little TOC dependence, suggesting some degree of depletion in these elements in the early Paleogene sediments of the Sanshui Basin. This probably resulted from cyclic recurrences of oxic benthic conditions, which promoted the remobilization of trace elements and caused the low concentration of trace elements.展开更多
文摘通过对榕江平原揭阳地区钻孔ZK01和ZK02硅藻记录的分析,结合沉积学特征和年代数据,重建榕江平原全新世以来的古环境演化。约10.4~8.5 ka B.P.,钻孔所在地尚未受到海水影响,发育河漫滩-淡水沼泽环境。8.5~5.5 ka B.P.海水入侵,形成潮间带沼泽-潮滩相沉积。5.5~3.9 ka B.P.本区为河口湾环境,约5.5 ka B.P.海侵影响达到最大,硅藻总丰度和分异度达到最高值。3.9~3.7 ka B.P.发生一次短暂海退,硅藻总丰度明显下降,ZK01孔发育咸水沼泽相沉积,ZK02孔仍为河口湾相沉积。3.7~2.4 ka B.P.海平面再次上升至相对稳定,研究区持续发育河口湾环境,期间出现3次小规模的水深变化旋回。2.4 ka B.P以来海水退出,河流作用增强,研究区发育三角洲平原相沉积。
基金the Natural Science Foundation of China (No. 40872024, 40272011)the Natural Science Foundation of Guangdong Province (No. 04009757), respectively
文摘The Honggang member of the early Paleogene Buxin Formation is the main source rock in the Sanshui Basin, characterized by organic-rich black shales with the cyclic recurrence of organic- poor sediments. The geochemical characteristics of the Honggang member have been documented to determine the organic matter types and depositional environments in this paper. The organic matter of the black shales mainly consists of a mixture of land plant-derived and phytoplankton-derived organic matter. Total organic carbon content （TOC）-sulfur-iron （Fe） relationships suggest that the organicrich black shales were deposited under dysoxic-to-euxinic water conditions. The time that iron minerals remained in contact with H2S in anoxic waters possibly influenced the formation of syngenetic pyrite, and organic carbon controlled the formation of diagenetic pyrite. Organic-poor intervals usually show pyrite sulfur enrichment and higher degree of pyritization values relative to low organic carbon contents. This resulted from HS- diffusing downward from overlying organic-rich sediments and formed Fe sulfides through reactions with sufficient Fe. Trace elements generally exhibit low concentrations and little TOC dependence, suggesting some degree of depletion in these elements in the early Paleogene sediments of the Sanshui Basin. This probably resulted from cyclic recurrences of oxic benthic conditions, which promoted the remobilization of trace elements and caused the low concentration of trace elements.
