The stratigraphic surface represented by a major contact between the Archean Bundelkhand Granite and the extensive Proterozoic Vindhyan sediments is a regional basement cover unconformity.This crystalline—sedimentary...The stratigraphic surface represented by a major contact between the Archean Bundelkhand Granite and the extensive Proterozoic Vindhyan sediments is a regional basement cover unconformity.This crystalline—sedimentary interface reflects an intense weathering of continental crust during marine transgression.Three time-transgressive sand deposition events viz.Kaimur,Rewa and Bhander are mainly witnessed during the entire Vindhyan sedimentation.Stratigraphically,the Upper Rewa Sandstone comprises one of these events in the Vindhyan Basin.Considerable progress has been made in interpreting these sandstones as a function of entirely marine process to a combination of tidal—fluvio—eolian activities.All the results have so far been attained on the basis of sedimentary facies,provenance,palaeocurrent analysis,and some of petrography.A distinct differentiation between marine and fluvial components of the Upper Rewa Sandstone still remains uncertain.Here,we use diagenesis as a parameter for the first time along with facies and palaeocurrent analysis to acquire a clear comprehension of marine-and fluvial-dominated processes.The present study spans 27 square kilometer area covering 15 stratigraphic sections with a collection of 571directional data from the facies specific sedimentary structures,and 28 samples obtained for the thin section analysis.The lower unit of the Upper Rewa Sandstone shows facies association typical of tidal environment,along with polymodal palaeocurrent.These rocks are well sorted and dominantly lithified by authigenic cement.Profuse development of a complex of syntaxial,passive pore fills,and grain replacive cements reflect normally pressured nature of the lower unit sandstones.The upper unit of the Upper Rewa Sandstone however,reveals a facies pattern resembling fluvial processes and unimodal palaeocurrent plot.They exhibit poor sorting,siliceous,and ferruginous matrix,and development of intense stylolites.Since,pressure solution is a dominant mode of lithification;the upper unit rocks therefore,are overpressured.Sand deposition event pertaining to the Upper Rewa Sandstone is found to comprise both marine and fluvial processes.Such a diagenesis based approach can be applied for marking a possible facies based unconformity between genetically different depositional units.展开更多
The present study documents three facies associations recorded from the Patherwa Formation. These facies are related to tidally influenced fluvial channel (Facies association A), tidal channel (Facies association B) a...The present study documents three facies associations recorded from the Patherwa Formation. These facies are related to tidally influenced fluvial channel (Facies association A), tidal channel (Facies association B) and tidal sand bar/tidal flat sandy facies (Facies association C). The spatio-temporal variation of these facies associations and palaeocurrent trends suggest tide dominated estuarine system. The estuaries were operational along a 60 km long NW-SE trending palaeo-shoreline. The Patherwa Formation grades up-section into facies packages of increasing tidal energy and terminate with the deposition within the upper flow regime estuarine settings.展开更多
The provenance of the lower Es2 in the Shanghe area was determined from an approach incorporating analysis, elemental ratios,paleocurrent direction,the typomorphic characteristics of detritus and the distribution of c...The provenance of the lower Es2 in the Shanghe area was determined from an approach incorporating analysis, elemental ratios,paleocurrent direction,the typomorphic characteristics of detritus and the distribution of conglomerate and gritstone in the peripheral basin.Typical elemental ratios characteristic of the sedimentary area were compared with those from the source areas as abstracted from sediments of the Huimin sag using cluster analysis.The results show that the distribution pattern focuses on Mg/Mn,Fe/K,Al/Na,Ba/Mn and Al/Mg.Mg/Mn is the highest ratio,from 25 to 45.This is similar to the pattern from the Precambrian.Furthermore,paleocurrent direction was used to determine provenance by examining the distribution of gritstone and the seismic progradational reflections.The research results indicate that the provenance is to the northwest in the Precambrian strata where the sand grain size is rough.To the east there is siltstone,fine sandstone and mudstone.This is significant for the exploration of oil and gas within the study area.展开更多
The measurement and analysis of the texture of sandstone can provide a lot of information and the basis for the palaeocurrent analysis, basin analysis and palaeoenvironmental reconstruction. Sedimentationists have don...The measurement and analysis of the texture of sandstone can provide a lot of information and the basis for the palaeocurrent analysis, basin analysis and palaeoenvironmental reconstruction. Sedimentationists have done a lot of researches in this field and proposed many theories and methods in the measurement of texture. But these methods are not satisfactory.展开更多
文摘The stratigraphic surface represented by a major contact between the Archean Bundelkhand Granite and the extensive Proterozoic Vindhyan sediments is a regional basement cover unconformity.This crystalline—sedimentary interface reflects an intense weathering of continental crust during marine transgression.Three time-transgressive sand deposition events viz.Kaimur,Rewa and Bhander are mainly witnessed during the entire Vindhyan sedimentation.Stratigraphically,the Upper Rewa Sandstone comprises one of these events in the Vindhyan Basin.Considerable progress has been made in interpreting these sandstones as a function of entirely marine process to a combination of tidal—fluvio—eolian activities.All the results have so far been attained on the basis of sedimentary facies,provenance,palaeocurrent analysis,and some of petrography.A distinct differentiation between marine and fluvial components of the Upper Rewa Sandstone still remains uncertain.Here,we use diagenesis as a parameter for the first time along with facies and palaeocurrent analysis to acquire a clear comprehension of marine-and fluvial-dominated processes.The present study spans 27 square kilometer area covering 15 stratigraphic sections with a collection of 571directional data from the facies specific sedimentary structures,and 28 samples obtained for the thin section analysis.The lower unit of the Upper Rewa Sandstone shows facies association typical of tidal environment,along with polymodal palaeocurrent.These rocks are well sorted and dominantly lithified by authigenic cement.Profuse development of a complex of syntaxial,passive pore fills,and grain replacive cements reflect normally pressured nature of the lower unit sandstones.The upper unit of the Upper Rewa Sandstone however,reveals a facies pattern resembling fluvial processes and unimodal palaeocurrent plot.They exhibit poor sorting,siliceous,and ferruginous matrix,and development of intense stylolites.Since,pressure solution is a dominant mode of lithification;the upper unit rocks therefore,are overpressured.Sand deposition event pertaining to the Upper Rewa Sandstone is found to comprise both marine and fluvial processes.Such a diagenesis based approach can be applied for marking a possible facies based unconformity between genetically different depositional units.
文摘The present study documents three facies associations recorded from the Patherwa Formation. These facies are related to tidally influenced fluvial channel (Facies association A), tidal channel (Facies association B) and tidal sand bar/tidal flat sandy facies (Facies association C). The spatio-temporal variation of these facies associations and palaeocurrent trends suggest tide dominated estuarine system. The estuaries were operational along a 60 km long NW-SE trending palaeo-shoreline. The Patherwa Formation grades up-section into facies packages of increasing tidal energy and terminate with the deposition within the upper flow regime estuarine settings.
基金supported by the National Natural Science Foundation of China(No.40972043)
文摘The provenance of the lower Es2 in the Shanghe area was determined from an approach incorporating analysis, elemental ratios,paleocurrent direction,the typomorphic characteristics of detritus and the distribution of conglomerate and gritstone in the peripheral basin.Typical elemental ratios characteristic of the sedimentary area were compared with those from the source areas as abstracted from sediments of the Huimin sag using cluster analysis.The results show that the distribution pattern focuses on Mg/Mn,Fe/K,Al/Na,Ba/Mn and Al/Mg.Mg/Mn is the highest ratio,from 25 to 45.This is similar to the pattern from the Precambrian.Furthermore,paleocurrent direction was used to determine provenance by examining the distribution of gritstone and the seismic progradational reflections.The research results indicate that the provenance is to the northwest in the Precambrian strata where the sand grain size is rough.To the east there is siltstone,fine sandstone and mudstone.This is significant for the exploration of oil and gas within the study area.
文摘The measurement and analysis of the texture of sandstone can provide a lot of information and the basis for the palaeocurrent analysis, basin analysis and palaeoenvironmental reconstruction. Sedimentationists have done a lot of researches in this field and proposed many theories and methods in the measurement of texture. But these methods are not satisfactory.
