Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we a...Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14 C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15–40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene(about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units(DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface(MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a highstand systems tract from middle Holocene(about 7–6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present.展开更多
To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D sei...To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.展开更多
High-resolution Chirp profiling and coring reveals an elongated （ca. 400 km） Holocene Zhujiang River （Pearl River）-derived mud area （maximum thickness 〉 20 m） extending from the Zhujiang River Delta, southwest-...High-resolution Chirp profiling and coring reveals an elongated （ca. 400 km） Holocene Zhujiang River （Pearl River）-derived mud area （maximum thickness 〉 20 m） extending from the Zhujiang River Delta, southwest-ward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the -120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the West-ern Pacific marginal seas （mainly Changjiang （Yangtze） and Huanghe （Yellow） Rivers derived） indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages： Stage 1 is before the mid-Holocene sea-level highstand （ca. 7.0 cal. ka BP）, the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse -1C; Stage 2, after the mid-Holocene sea-level highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5-10 m water depth to less than 1-2 m around 20-30 m water depth. In addition, we also find a de-veloped distal clinoform in the east of the Leizhou Peninsula.展开更多
A banner bank off the north coast of the Chengshan Headland, Shandong Peninsula, has been described on the basis of echo sounder bathymetry, side-scan sonar and high-resolution seismic data sets. The bank is in NWW di...A banner bank off the north coast of the Chengshan Headland, Shandong Peninsula, has been described on the basis of echo sounder bathymetry, side-scan sonar and high-resolution seismic data sets. The bank is in NWW direction, approximately parallel to the coastline. The bank consists of sandy silt or clayed silt. Sand waves and megaripples are observed on the north side, which result from strong tidal currents around the headland and storm waves in winter. These bed forms indicate that the bank is influenced by the modern hydrodynamics. The bank is separated from the coast and Holocene subaqueous clinoform around the Shandong Peninsula in its east part. High-resolution seismic profiles reveal that the bank was formed during two periods： the earlier seismic unit Ua, and later seismic units Ub and Uc which overlays Ua with erosional surfaces on its south side and north side, respectively. As comparing with the clinoform, the bank has a different internal architecture. In the west of the bank, however, topography and surface sediment characteristics suggest that the bank links to the clinoform. The authors propose that seismic Ua is a residual part of early clinoform deposit. After the sediments in the north and south of Ua were eroded by strong currents, the Ub and Uc started to deposit probably by a complex hydrodynamic process. These results provide new insights into the evolution of the bank and its relation with the Holocene subqueous clinoform.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 41306063 and 41330964)by the China Geological Survey (Nos. GZH200900501 and GZH201100203)
文摘Based on the stratigraphic sequence formed since the last glaciation and revealed by 3000 km long high-resolution shallow seismic profiles and the core QDZ03 acquired recently off the southern Shandong Peninsula, we addressed the sedimentary characteristics of a Holocene subaqueous clinoform in this paper. Integrated analyses were made on the core QDZ03, including sedimentary facies, sediment grain sizes, clay minerals, geochemistry, micro paleontology, and AMS 14 C dating. The result indicates that there exists a Holocene subaqueous clinoform, whose bottom boundary generally lies at 15–40 m below the present sea level with its depth contours roughly parallel to the coast and getting deeper seawards. The maximum thickness of the clinoform is up to 22.5 m on the coast side, and the thickness contours generally spread in a banded way along the coastline and becomes thinner towards the sea. At the mouths of some bays along the coast, the clinoform stretches in the shape of a fan and its thickness is evidently larger than that of the surrounding sediments. This clinoform came into being in the early Holocene(about 11.2 cal kyr BP) and can be divided into the lower and upper depositional units(DU 2 and DU 1, respectively). The unit DU 2, being usually less than 3 m in thickness and formed under a low sedimentation rate, is located between the bottom boundary and the Holocene maximum flooding surface(MFS), and represents the sediment of a post-glacial transgressive systems tract; whereas the unit DU 1, the main body of the clinoform, sits on the MFS, belonging to the sediment of a highstand systems tract from middle Holocene(about 7–6 cal kyr BP) to the present. The provenance of the clinoform differs from that of the typical sediments of the Yellow River and can be considered as the results of the joint contribution from both the Yellow River and the proximal coastal sediments of the Shandong Peninsula, as evidenced by the sediment geochemistry of the core. As is controlled mainly by coactions of multiple factors such as the Holocene sea-level changes, sediment supplies and coastal dynamic conditions, the development of the clinoform is genetically related with the synchronous clinoform or subaqueous deltas around the northeastern Shandong Peninsula and in the northern South Yellow Sea in the spatial distribution and sediment provenance, as previously reported, with all of them being formed from the initial stage of the Holocene up to the present.
基金Supported by the National Science and Technology Major Project(2017ZX05001)CNPC Technology Project(2023YQX20111).
文摘To address the discrepancies between well and seismic data in stratigraphic correlation of the Triassic Yanchang Formation in the Ordos Basin,NW China,traditional stratigraphic classification schemes,the latest 3D seismic and drilling data,and reservoir sections are thoroughly investigated.Guided by the theory of sequence stratigraphy,the progradational sequence stratigraphic framework of the Yanchang Formation is systematically constructed to elucidate new deposition mechanisms in the depressed lacustrine basin,and it has been successfully applied to the exploration and development practices in the Qingcheng Oilfield.Key findings are obtained in three aspects.First,the seismic progradational reflections,marker tuff beds,and condensed sections of flooding surfaces in the Yanchang Formation are consistent and isochronous.Using flooding surface markers as a reference,a progradational sequence stratigraphic architecture is reconstructed for the middle-upper part of Yanchang Formation,and divided into seven clinoform units(CF1-CF7).Second,progradation predominantly occurs in semi-deep to deep lake environments,with the depositional center not always coinciding with the thickest strata.The lacustrine basin underwent an evolution of“oscillatory regression-progradational infilling-multi-phase superimposition”.Third,the case study of Qingcheng Oilfield reveals that the major pay zones consist of“isochronous but heterochronous”gravity-flow sandstone complexes.Guided by the progradational sequence stratigraphic architecture,horizontal well oil-layer penetration rates remain above 82%.The progradational sequence stratigraphic architecture and associated geological insights are more consistent with the sedimentary infilling mechanisms of large-scale continental depressed lacustrine basins and actual drilling results.The research results provide crucial theoretical and technical support for subsequent refined exploration and development of the Yanchang Formation,and are expected to offer a reference for research and production practice in similar continental lacustrine basins.
基金The National Natural Science Foundation of China under contract Nos 41106045 and 41206045the Scientific Research Fund of the Second Institute of Oceanography,SOA under contract No.JT1102the Basic Research Fund of State Oceanic Administration(named as Pale-oceanographic Research in the Western Pacific)
文摘High-resolution Chirp profiling and coring reveals an elongated （ca. 400 km） Holocene Zhujiang River （Pearl River）-derived mud area （maximum thickness 〉 20 m） extending from the Zhujiang River Delta, southwest-ward off the Guangdong coast, to the Leizhou Peninsula. Two depo-centers, one proximal and one distal, are identified. On the continental shelf off the west Guangdong Province, the mud is deposited in water depth shallower than 50 m; while to the southeast of the Zhujiang River Estuary, the mud area can extend to the -120 m isobath. A combined analysis with the stratigraphic sequences of other muddy deposits in the West-ern Pacific marginal seas （mainly Changjiang （Yangtze） and Huanghe （Yellow） Rivers derived） indicates that the initiation of the Zhujiang River muddy deposit can be further divided into two stages： Stage 1 is before the mid-Holocene sea-level highstand （ca. 7.0 cal. ka BP）, the proximal mud was mostly deposited after 9.0 cal. ka BP, when the sea-level rose slowly after the Meltwater Pulse -1C; Stage 2, after the mid-Holocene sea-level highstand, clinoform developed on the continental shelf off the west Guangdong Province, extending ca. 400 km from the Zhujiang River Estuary. The proximal clinoform thins offshore, from ca. 10 m thickness around 5-10 m water depth to less than 1-2 m around 20-30 m water depth. In addition, we also find a de-veloped distal clinoform in the east of the Leizhou Peninsula.
基金China Geological Survey under contract No 200311000005"973" Project under contract No 2005CB422304
文摘A banner bank off the north coast of the Chengshan Headland, Shandong Peninsula, has been described on the basis of echo sounder bathymetry, side-scan sonar and high-resolution seismic data sets. The bank is in NWW direction, approximately parallel to the coastline. The bank consists of sandy silt or clayed silt. Sand waves and megaripples are observed on the north side, which result from strong tidal currents around the headland and storm waves in winter. These bed forms indicate that the bank is influenced by the modern hydrodynamics. The bank is separated from the coast and Holocene subaqueous clinoform around the Shandong Peninsula in its east part. High-resolution seismic profiles reveal that the bank was formed during two periods： the earlier seismic unit Ua, and later seismic units Ub and Uc which overlays Ua with erosional surfaces on its south side and north side, respectively. As comparing with the clinoform, the bank has a different internal architecture. In the west of the bank, however, topography and surface sediment characteristics suggest that the bank links to the clinoform. The authors propose that seismic Ua is a residual part of early clinoform deposit. After the sediments in the north and south of Ua were eroded by strong currents, the Ub and Uc started to deposit probably by a complex hydrodynamic process. These results provide new insights into the evolution of the bank and its relation with the Holocene subqueous clinoform.
