Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the n...Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the nondisputed deltaic environment was marine or continental.This dispute cannot be solved by mere sedimentological analysis and,moreover,too few fossils are present to be decisive.展开更多
The Late Cambrian(Furongian)Chaomidian Formation accumulated in an epeiric sea that covered a large part of the North China Plate and extended from China to Korea.The depositional environment of the formation is commo...The Late Cambrian(Furongian)Chaomidian Formation accumulated in an epeiric sea that covered a large part of the North China Plate and extended from China to Korea.The depositional environment of the formation is commonly considered to have been affected by storms that broke up numerous limestone layers,but that was tectonically quiet.It is here argued,however,that some features of the formation-more in particular the many dozens of breccia layers and the occurrence of slid-down limestone blocks that are embedded in autochthonous oolites-can be explained satisfactorily only if some significant fault activity took place during its accumulation.The faulting may have been due to differential loading and subsidence,but an endogenic origin seems more probable.This implies that the structural history of the study area in Shandong Province may need re-consideration.展开更多
The brackish lagoon in the central part of The Netherlands was closed by a dike in 1932 and gradually changed into a lake.Parts of this lake were reclaimed and the surficial sediments of one of the polders(Noordoostpo...The brackish lagoon in the central part of The Netherlands was closed by a dike in 1932 and gradually changed into a lake.Parts of this lake were reclaimed and the surficial sediments of one of the polders(Noordoostpolder),reclaimed in 1942,has been investigated in detail by mapping of the walls of some1500 km of drainage ditches approx.1.4 m deep.It appeared that the sediments consist of an uncommonly large amount of silt,to different degrees mixed with reworked peat that had developed during the Holocene transgression.Some sandy deposits occur locally,at places that are at first sight distributed in a haphazard way.The various sandy patches have different characteristics(grain-size distribution,rounding of the grains,mineral composition).These sands cannot have been introduced from the sea,nor can they have been supplied by the rivers that discharged into the lagoon,so they must have a local origin.It is found that several types of Pleistocene sandy or diamictic deposits below the Holocene peat and lagoonal sediments had an irregular topography and became eroded during the Holocene by wave activity.This resulted in sandy deposits around these Pleistocene highs,which consisted of glacial tills(boulder clays),river dunes(formed by aeolian activity along rivers under dry permafrost conditions)and coversand ridges,formed by aeolian activity in a belt between the ice margin and the more distal loess belt.This finding implies that palaegeographical interpretations of local grain-size anomalies in a specific deposit should not only consider facies changes due to changes in the sediment supply,but should also consider local erosion leading to the exposure of previously deposited material with a divergent composition.展开更多
Sedimentary successions in the northwestern Gulf of Suez provide important clues to the understanding of the geological evolution of NE Africa during the middle and late Eocene.This study focuses on detailed facies an...Sedimentary successions in the northwestern Gulf of Suez provide important clues to the understanding of the geological evolution of NE Africa during the middle and late Eocene.This study focuses on detailed facies analyses in order to characterize the depositional environments and system tracts of the Bartonian-Priabonian succession cropping out in this area.Bartonian-Priabonian carbonate deposits in five stratigraphic sections constitute,from base to top,the Gebel Hof,Observatory,Sannur,Qurn,and Wadi Hof Formations.These formations contain four local assemblage zones of larger benthic foraminifers.Analyses of litho-,bio-,and microfacies in the succession resulted in the recognition of 12 lithofacies types.These lithofacies are represented by packages of lime-mudstones,wackestones,packstones,pack-to grainstones,grainstones,rudstones,boundstones and dolomites.These lithofacies have been grouped into four geneticallyrelated facies associations that represent,respectively,tidal flats/shallow subtidal,restricted-shelf/lagoonal,shoal bar,and outer-shelf lagoon/reefal depositional environments in a downslope shallow-marine inner-ramp setting.The vertical transitions of these facies associations,representing facies changes through time,imply fluctuations of the regional sea level.The two peaks in the Bartonian correspond to well-known global eustatic sea-level rises;the pronounced Priabonian regression must be ascribed to the known global eustatic sea-level fall in combination with regional tectonic activity.The facies distribution suggests that the study area was located in the direct vicinity of some islands during the Bartonian-Priabonian.展开更多
基金supported by the National Natural Science Foundation of China (grants No.41372135 and 41672120)Shandong University of Science and Technology Research Fund (grant No.2015TDJH101)
文摘Objective A succession with well-developed soft-sediment deformation structures and well-exposed gravity-flow deposits in the Early Cretaceous Lingshandao Formation has caused considerable controversy on whether the nondisputed deltaic environment was marine or continental.This dispute cannot be solved by mere sedimentological analysis and,moreover,too few fossils are present to be decisive.
基金the China-Association of Southeast Asian Nations(ASEAN)Maritime Cooperation Fund(grant No.12120100500017001)the China National Natural Science Foundation Project(grant No.41672120)the Shandong University of Science and Technology(SDUST)Research Fund(grant No.2015TDJH101)for their financial support。
文摘The Late Cambrian(Furongian)Chaomidian Formation accumulated in an epeiric sea that covered a large part of the North China Plate and extended from China to Korea.The depositional environment of the formation is commonly considered to have been affected by storms that broke up numerous limestone layers,but that was tectonically quiet.It is here argued,however,that some features of the formation-more in particular the many dozens of breccia layers and the occurrence of slid-down limestone blocks that are embedded in autochthonous oolites-can be explained satisfactorily only if some significant fault activity took place during its accumulation.The faulting may have been due to differential loading and subsidence,but an endogenic origin seems more probable.This implies that the structural history of the study area in Shandong Province may need re-consideration.
基金supported by the China-ASEAN(Association of Southeast Asian Nations)Maritime Cooperation Fund Project(grant No.12120100500017001)the National Natural Science Foundation of China(grant No.41972146)。
文摘The brackish lagoon in the central part of The Netherlands was closed by a dike in 1932 and gradually changed into a lake.Parts of this lake were reclaimed and the surficial sediments of one of the polders(Noordoostpolder),reclaimed in 1942,has been investigated in detail by mapping of the walls of some1500 km of drainage ditches approx.1.4 m deep.It appeared that the sediments consist of an uncommonly large amount of silt,to different degrees mixed with reworked peat that had developed during the Holocene transgression.Some sandy deposits occur locally,at places that are at first sight distributed in a haphazard way.The various sandy patches have different characteristics(grain-size distribution,rounding of the grains,mineral composition).These sands cannot have been introduced from the sea,nor can they have been supplied by the rivers that discharged into the lagoon,so they must have a local origin.It is found that several types of Pleistocene sandy or diamictic deposits below the Holocene peat and lagoonal sediments had an irregular topography and became eroded during the Holocene by wave activity.This resulted in sandy deposits around these Pleistocene highs,which consisted of glacial tills(boulder clays),river dunes(formed by aeolian activity along rivers under dry permafrost conditions)and coversand ridges,formed by aeolian activity in a belt between the ice margin and the more distal loess belt.This finding implies that palaegeographical interpretations of local grain-size anomalies in a specific deposit should not only consider facies changes due to changes in the sediment supply,but should also consider local erosion leading to the exposure of previously deposited material with a divergent composition.
文摘Sedimentary successions in the northwestern Gulf of Suez provide important clues to the understanding of the geological evolution of NE Africa during the middle and late Eocene.This study focuses on detailed facies analyses in order to characterize the depositional environments and system tracts of the Bartonian-Priabonian succession cropping out in this area.Bartonian-Priabonian carbonate deposits in five stratigraphic sections constitute,from base to top,the Gebel Hof,Observatory,Sannur,Qurn,and Wadi Hof Formations.These formations contain four local assemblage zones of larger benthic foraminifers.Analyses of litho-,bio-,and microfacies in the succession resulted in the recognition of 12 lithofacies types.These lithofacies are represented by packages of lime-mudstones,wackestones,packstones,pack-to grainstones,grainstones,rudstones,boundstones and dolomites.These lithofacies have been grouped into four geneticallyrelated facies associations that represent,respectively,tidal flats/shallow subtidal,restricted-shelf/lagoonal,shoal bar,and outer-shelf lagoon/reefal depositional environments in a downslope shallow-marine inner-ramp setting.The vertical transitions of these facies associations,representing facies changes through time,imply fluctuations of the regional sea level.The two peaks in the Bartonian correspond to well-known global eustatic sea-level rises;the pronounced Priabonian regression must be ascribed to the known global eustatic sea-level fall in combination with regional tectonic activity.The facies distribution suggests that the study area was located in the direct vicinity of some islands during the Bartonian-Priabonian.