Many reefs of the Late Paleozoic have been discovered recently in the Hinggan-lnner Mongolia area. These reefs clearly are geographically extensive, and possess distinctive features and well-developed reef-facies. The...Many reefs of the Late Paleozoic have been discovered recently in the Hinggan-lnner Mongolia area. These reefs clearly are geographically extensive, and possess distinctive features and well-developed reef-facies. They have been found to contain five reef-building communities and were constructed in four periods. Colonial coral-algal reefs at Aohan and Chifeng represent a warm shallow-sea in the Carboniferous. Different reefs in the Xiwu Banner were formed in three periods： early Late Carboniferous, late Late Carboniferous and Early Permian. These reefs were built in warm sea conditions. Their buildup types include colonial coral frameworks, algae-buildings and lime-mud mounds. Bryozoan reefs in the Zhalaite and Dongwu banners were built in the late Middle Permian and thrived in a cold shallow-sea. All reefs grew independently on two kinds of sedimentary platforms, carbonate and carbonate-clastic mixed platforms. Four reef-forming periods occurred later from south to north, along a collisional course between the North China Plate and the Siberian Plate. These reefs can be arranged into three ＇reef-links＇ or reef zones that extend along plate margins. Among these, the Aohan-Chifeng reef-link indicates a northern margin of the North China Plate, the Zhalaite-Dongwu reef-link marks a southern margin of the Siberian Plate, and the Xiwu-Beishan reef-link reflects the former existence of some inter-plates. The strata of each reef-facies are thick and contain rich asphalt deposits. Overlapping and heteropic layers are very thick and contain dark oil/gas-rich horizons; TOC analyses verify that most of these are good hydrocarbon source rocks. This study shows that the study area is an excellent candidate for oil-gas exploration.展开更多
A sediment-continuous section of Jurassic-Cretaceous (J-K) boundary strata was found in Zhangjiagou of Luanping, northern Hebei Province, China. The boundary strata were systematically divided into 5 sequences, 13 sub...A sediment-continuous section of Jurassic-Cretaceous (J-K) boundary strata was found in Zhangjiagou of Luanping, northern Hebei Province, China. The boundary strata were systematically divided into 5 sequences, 13 subsequences and 139 parasequences by sedimentary cyclicities and facies analysis. According to stable time-ranges of subsequences and parasequences, some boundary ages can be marked as 142.90 Ma of the SQ I (Dabeigou Fm) basal bound, 141.16 Ma of the SQ II basal bound, 140.00 Ma of the SQ III (Dadianzi Fm) basal bound, 138.24 Ma of the SQ VI (Zhangjiagou Fm) basal bound and 135.34 Ma of the SQ V (Zhangjiagou Fm) top-bound. A sequence-stratigraphic framework of the Dabeigou-Zhangjiagou Fms has been constructed by tracing sequence-bounds, marker-beds and fossil zones. The basin-development and tectonic activities are studied based on sequence-stratigraphic evidence. 5 sequences represent 5 tectonic cycles and all the 6 sequence-bounds reflect tectonic activities. Tectonic activities clearly influence the basin-development that can be divided into 3 stages in the J-K transitional period. Each stage consists of a down-faulting-rising process, i.e. from strongly rising of basin-bottom, then violently faulting down (with volcanic eruptions) and to gently rising. The development shows a pattern of bottom down-faulting with basin narrowing and rising with spreading. Keywords sequence - stratigraphy - terrestrial stratotype - Jurassic-Cretaceous bound DOI: 10.1360/03yd0451展开更多
基金supported by the Geological Survey of China (Grant No. 1212010782004)National Natural Science Foundation of China (Grant No. 41072021)
文摘Many reefs of the Late Paleozoic have been discovered recently in the Hinggan-lnner Mongolia area. These reefs clearly are geographically extensive, and possess distinctive features and well-developed reef-facies. They have been found to contain five reef-building communities and were constructed in four periods. Colonial coral-algal reefs at Aohan and Chifeng represent a warm shallow-sea in the Carboniferous. Different reefs in the Xiwu Banner were formed in three periods： early Late Carboniferous, late Late Carboniferous and Early Permian. These reefs were built in warm sea conditions. Their buildup types include colonial coral frameworks, algae-buildings and lime-mud mounds. Bryozoan reefs in the Zhalaite and Dongwu banners were built in the late Middle Permian and thrived in a cold shallow-sea. All reefs grew independently on two kinds of sedimentary platforms, carbonate and carbonate-clastic mixed platforms. Four reef-forming periods occurred later from south to north, along a collisional course between the North China Plate and the Siberian Plate. These reefs can be arranged into three ＇reef-links＇ or reef zones that extend along plate margins. Among these, the Aohan-Chifeng reef-link indicates a northern margin of the North China Plate, the Zhalaite-Dongwu reef-link marks a southern margin of the Siberian Plate, and the Xiwu-Beishan reef-link reflects the former existence of some inter-plates. The strata of each reef-facies are thick and contain rich asphalt deposits. Overlapping and heteropic layers are very thick and contain dark oil/gas-rich horizons; TOC analyses verify that most of these are good hydrocarbon source rocks. This study shows that the study area is an excellent candidate for oil-gas exploration.
文摘A sediment-continuous section of Jurassic-Cretaceous (J-K) boundary strata was found in Zhangjiagou of Luanping, northern Hebei Province, China. The boundary strata were systematically divided into 5 sequences, 13 subsequences and 139 parasequences by sedimentary cyclicities and facies analysis. According to stable time-ranges of subsequences and parasequences, some boundary ages can be marked as 142.90 Ma of the SQ I (Dabeigou Fm) basal bound, 141.16 Ma of the SQ II basal bound, 140.00 Ma of the SQ III (Dadianzi Fm) basal bound, 138.24 Ma of the SQ VI (Zhangjiagou Fm) basal bound and 135.34 Ma of the SQ V (Zhangjiagou Fm) top-bound. A sequence-stratigraphic framework of the Dabeigou-Zhangjiagou Fms has been constructed by tracing sequence-bounds, marker-beds and fossil zones. The basin-development and tectonic activities are studied based on sequence-stratigraphic evidence. 5 sequences represent 5 tectonic cycles and all the 6 sequence-bounds reflect tectonic activities. Tectonic activities clearly influence the basin-development that can be divided into 3 stages in the J-K transitional period. Each stage consists of a down-faulting-rising process, i.e. from strongly rising of basin-bottom, then violently faulting down (with volcanic eruptions) and to gently rising. The development shows a pattern of bottom down-faulting with basin narrowing and rising with spreading. Keywords sequence - stratigraphy - terrestrial stratotype - Jurassic-Cretaceous bound DOI: 10.1360/03yd0451
