A combined micropalaeontological and sedimentological investigation of the Early Eocene Naredi Formation (thickness varying between 20 m and 60 m) reveals a complete third-order cycle and six fourth-order sea level cy...A combined micropalaeontological and sedimentological investigation of the Early Eocene Naredi Formation (thickness varying between 20 m and 60 m) reveals a complete third-order cycle and six fourth-order sea level cycles. Within the third-order cycle the foraminiferal abundance and diversity gradually increase upwards and reach their maximum values at about 41 m thickness above the base of the formation and subsequently decrease upward and finally give way upward to an unfossiliferous zone at the topmost part. Within a fourth-order cycle foraminiferal abundance and diversity exhibit a similar increasing and decreasing pattern. Bounded between two unconformities the Naredi Formation represents a sequence. A highly fossiliferous Assilinabearing limestone interval represents the maximum flooding zone which separates the transgressive systems tract at the base from the highstand systems tract at the top.展开更多
The non-marine strata of the Ypresian Naredi Formation have been deposited and intermittently pedogenized after the culmination of the Early Eocene Climatic Optimum(EECO).This continental interval comprises intercalat...The non-marine strata of the Ypresian Naredi Formation have been deposited and intermittently pedogenized after the culmination of the Early Eocene Climatic Optimum(EECO).This continental interval comprises intercalation of laterite and palaeosol horizons developed by cyclic episodes of erosion,subaerial exposure,and deposition.The palaeopedological analyses investigate the morphological and micromorphological features evidencing repeated subaerial exposure and consequently moderate to well-developed palaeosol horizons.The topmost laterite bed records an intensely bioturbated ichnofabric(consisting of the root traces and the composite ichnotaxa of lungfish aestivation burrows,Macanopsis(possible arachnid burrows),and Skolithos.The pedogenized shale horizons contain the paucispecific Camborygma-root trace ichnofabric with highly localized patchy preservation of Camborygma symplokonomos,Camborygma eumekenomos,and rhizoturbation.The ichnospecies variation of Camborygma along with the ichnofabric analyses led to the demarcation of stratigraphic horizons and evaluation of the palaeowater-table fluctuations vis-a-vis the low-order allocyclicity,the ethology of producers,and the depositional setting.The paucispecific suite of trace fossils refers to the Camborygma Ichnofacies,where the substrate is intermittently pedogenized and lateritized with upward increasing thickness of beds and intensity of pedogenesis,lateritization,ichnodiversity,and ichnoabundance.Hence,as an expression of high-frequency(interpreted as 5th-order)stratigraphic fluctuations within an early Falling Stage Systems Tract(FSST),a hot palaeoclimate with seasonality varying between humid inundated to dry desiccated conditions is interpreted with the palaeowater table being the base-level control.It culminates with the driest condition at the top with the thickest laterite development associated with the RAeMaS ichnofabric.With the onset of early transgression as documented in the overlying marine deposits of the Bartonian Harudi Formation,the top of the studied interval marks an induced subaerial unconformity.展开更多
基金financial support (project No. SR/S4/ESe281/2007)
文摘A combined micropalaeontological and sedimentological investigation of the Early Eocene Naredi Formation (thickness varying between 20 m and 60 m) reveals a complete third-order cycle and six fourth-order sea level cycles. Within the third-order cycle the foraminiferal abundance and diversity gradually increase upwards and reach their maximum values at about 41 m thickness above the base of the formation and subsequently decrease upward and finally give way upward to an unfossiliferous zone at the topmost part. Within a fourth-order cycle foraminiferal abundance and diversity exhibit a similar increasing and decreasing pattern. Bounded between two unconformities the Naredi Formation represents a sequence. A highly fossiliferous Assilinabearing limestone interval represents the maximum flooding zone which separates the transgressive systems tract at the base from the highstand systems tract at the top.
基金Science and Engineering Research Board(SERB),Government of India(grant#CRG/2018/000259 to SDG)Industrial Research and Consultancy Centre(IRCC),IIT Bombay(seed grant#RD/0517-IRCCSH0-035 to SDG and final-year scholarship to MD)+1 种基金IITB and Ministry of Education,Government of India(doctoral scholarship for MD)Council of Scientific&Industrial Research(CSIR)(doctoral scholarship for RD.
文摘The non-marine strata of the Ypresian Naredi Formation have been deposited and intermittently pedogenized after the culmination of the Early Eocene Climatic Optimum(EECO).This continental interval comprises intercalation of laterite and palaeosol horizons developed by cyclic episodes of erosion,subaerial exposure,and deposition.The palaeopedological analyses investigate the morphological and micromorphological features evidencing repeated subaerial exposure and consequently moderate to well-developed palaeosol horizons.The topmost laterite bed records an intensely bioturbated ichnofabric(consisting of the root traces and the composite ichnotaxa of lungfish aestivation burrows,Macanopsis(possible arachnid burrows),and Skolithos.The pedogenized shale horizons contain the paucispecific Camborygma-root trace ichnofabric with highly localized patchy preservation of Camborygma symplokonomos,Camborygma eumekenomos,and rhizoturbation.The ichnospecies variation of Camborygma along with the ichnofabric analyses led to the demarcation of stratigraphic horizons and evaluation of the palaeowater-table fluctuations vis-a-vis the low-order allocyclicity,the ethology of producers,and the depositional setting.The paucispecific suite of trace fossils refers to the Camborygma Ichnofacies,where the substrate is intermittently pedogenized and lateritized with upward increasing thickness of beds and intensity of pedogenesis,lateritization,ichnodiversity,and ichnoabundance.Hence,as an expression of high-frequency(interpreted as 5th-order)stratigraphic fluctuations within an early Falling Stage Systems Tract(FSST),a hot palaeoclimate with seasonality varying between humid inundated to dry desiccated conditions is interpreted with the palaeowater table being the base-level control.It culminates with the driest condition at the top with the thickest laterite development associated with the RAeMaS ichnofabric.With the onset of early transgression as documented in the overlying marine deposits of the Bartonian Harudi Formation,the top of the studied interval marks an induced subaerial unconformity.
