Abstract

Drilling results from mid-Pacific atoll and archipelagic apron sites in the Line Islands and Marshall Islands provinces lead to the conclusion that Oligocene sea-level falls detected in Atlantic passive margin sequences are also recorded in a mid-plate-tectonic setting in the Pacific Basin. The mid-Pacific sea-level falls are recorded by (a) the presence of distinct, coarse-grained, graded beds of turbidite origin, rich in reef-derived skeletal debris of Oligocene, Eocene, and Cretaceous age, that were redeposited in deep-water archipelagic apron carbonate sequences of middle and late Oligocene age now flanking the atolls and (b) a marked stratigraphic hiatus and solution unconformity in the subsurface of Enewetak atoll which dates an Oligocene period of atoll emergence correlative with both the deposition of the turbidites and the coastal offlap events discerned in Atlantic passive margins. Correlation of the subsidence path of Enewetak atoll with the development of the Oligocene solution unconformity shows that ca. 30 Ma sea level was as much as 100 m lower than at present.

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