Abstract

Basinal and platformal rocks of the northern part of the Mesozoic marine province of northwestern Nevada are juxtaposed along the curvilinear trace of the late Mesozoic Fencemaker thrust fault. The allochthonous rocks form a belt of basin-facies deposits that accumulated in upper- to mid-submarine fan environments that parallel the trace of the regional thrust. Lower submarine-fan or basin-floor facies are recognized but consistently are west of the more proximal deposits and lie in structurally higher positions within the Fencemaker allochthon. The thrust fault apparently follows the transitional zone between the basinal rocks composing the upper plate and the easterly parautochthonous platformal rocks.

The basin facies sediments were derived from two sources in the Late Triassic and Early Jurassic periods. One source supplied siliciclastic debris, whereas the other contributed sporadic but copious amounts of shallow-marine carbonate debris. The two sources operated independently and simultaneously supplied sediments to different parts of the basinal environment.

The platform assemblage was dominated by deltaic and carbonate reef and continental shelf environments. The site of deltaic sedimentation migrated with time, producing compositional differences in the detritus being fed into the adjacent basinal areas to the west.

Sedimentation rates within the basinal environment exceeded subsidence, causing the basin to fill and shoal with time. The basin facies rocks are gradationally overlain by westward-prograding platform carbonate rocks and rocks representing prodeltaic environments. Early to Middle Jurassic synorogenic sediments derived both from local sources and from probable cratonic sources dominated the final episode of deposition. The synorogenic sediments accumulated in shallow-marine to subaerial environments localized by structures associated with regional extension.

First Page Preview

First page PDF preview
You do not currently have access to this article.