Depositional responses of the interaction between deep-marine gravity and bottom currents and their exploration significance
The interaction between down-slope gravity flows(turbidity currents)and along-slope bottom currents(contour currents)is the frontier area and underappreciated topic of the current research on deep-water sedimentology,with poor understanding of its resultant depositional systems and associated sedimentological characteristics.The present study reveals morphometrics,sedimentological characteristics,and growth patterns of two typical depositional systems created by the interplay of gravity and bottom currents,and explores distribution pattern and diagnostic criteria for the recognition of potentially productive deep-water reservoirs created by the interplay of gravity and bottom currents.Unidirectionally migrating deep-water channels are characterized by asymmetrical cross-sectional geometries and unidirectional growth patterns,and can be subdivided into unidirectionally upstream-migrating channels(i.e.,channels migrating against the direction of bottom currents)and unidirectionally downstream-migrating channels(i.e.,channels migrating along the direction of bottom currents).Unidirectionally migrating submarine lobes are characterized by plan-view morphology with long axis direction parallel to regional contour lines and by growth pattern with extension direction parallel to the depositional strike of regional slope.Bottom-current reworked sands created by the interplay of gravity and bottom currents are distinguished from turbiditic sands by rich in bioskeletons and shell fragments,a lack of age inversion,sharp,non-erosional,upper contacts,and by the occurrence of traction structures(i.e.,two to tripartite subdivisions of cumulative frequency plots,unimodal distribution patterns of frequency-distribution curves,in the traction zone of CM diagrams).These sedimentological characteristics,in turn,can be taken as diagnostic criteria for the recognition of bottom-current reworked sands.Spatially,bottom-current reworked sands are preferentially deposited to the side toward which the channels migrated,and exhibit a spatial distribution pattern characterized by unidirectional migration and orderly distribution.Temporally,they are characterized by the asymmetrical,L-shaped plan-view morphology,and display characterized by unidirectional offset and lateral migration.Spatiotemporally,bottom-current reworked sands laterally migrated and stacked along the direction of regional contour lines,forming giant,potentially productive deep-water reservoirs.
the interplay of gravity and bottom currentsunidirectionally migrating deep-water channelsunidirectionally migrating submarine lobesbottom-current reworked sands
万方数据
维普
