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Sequences, systems tracts, and eustatic cycles

Conference ·
OSTI ID:5969357
Depositional sequences are composed of genetically related sediments bounded by unconformities or their correlative conformities and are related to cycles of eustatic change. The bounding unconformities are inferred to be related to eustatic fall inflection points. Four systems tracts are recognized: lowstand, transgressive, highstand, and shelf margin systems tracts. The lowstand systems tract is subdivided into two parts: lowstand fan and lowstand wedge where the basin margin is characterized by a discrete physiographic shelf edge, or lower and upper wedge where the basin margin is characterized by a ramp physiography. Each systems tract is comprised of a linkage of contemporaneous depositional systems. Unconformities are characterized by a basin-ward shift of coastal onlap concomitant with a cessation of fluvial deposition. The style of subaerial erosion characterizing each unconformity is different. Type 1 unconformities are characterized by stream rejuvenation and incision, whereas Type 2 unconformities typically are characterized by widespread erosion accompanying gradual denudation or degradation of the landscape. Stream rejuvenation and incision are not associated with this type of unconformity.
OSTI ID:
5969357
Report Number(s):
CONF-880301-
Country of Publication:
United States
Language:
English

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