About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

Journal of Sedimentary Research (SEPM)

Abstract


Journal of Sedimentary Petrology
Vol. 42 (1972)No. 2. (June), Pages 318-324

Fair Previous HitWeatherNext Hit Versus Storm Processes in Shallow Marine Sand Bar Sequences in the Late Precambrian of Finnmark, North Norway

D. K. Hobday (2), H. G. Reading

ABSTRACT

A 30m succession of late Precambrian quartzose sandstones at Skallneset, Finnmark, north Norway, is subdivided into five sequences which coarsen upward and contain three facies which occur in a preferred vertical order of deposition A ^rarr B ^rarr C. Overlying and underlying strata indicate a shallow marine environment.

Facies A (siltstone facies) consists of horizontally bedded siltstones and sandstones, with abundant symmetrical ripples trending predominantly NW-SE. It is interpreted as resulting from alternating periods of deposition from suspension during fair Previous HitweatherNext Hit, and of wave oscillation during storms. Facies B (major foreset facies) consists of sandstones with small-scale trough cross-bedding directed northward, separated by westward inclined surfaces which are largely erosional in origin. East-west trending symmetrical ripples sometimes occur on these surfaces. This facies is interpreted as the product of a westward buildout of sandbars by deposition from northward flowing semi-permanent currents, interrupted by occasional storms which truncated the western margins of the bars. Facies C (s all-scale trough cross-bedded facies) consists of sandstones containing undulatory scoured surfaces, trough cross-bedding dipping northwestwards, and ripples striking N-S and NW-SE. It is interpreted as due to northward flowing semi-permanent currents interrupted by occasional storms.

The characteristics of the individual sequences appear to be the result of two distinct regimes, one dominated by fair Previous HitweatherNext Hit (constructional) and one by storms (destructional). The fair Previous HitweatherTop regime is indicated by the northward dipping trough cross-beds deposited by semi-permanent currents. The storm regime is indicated by the large-scale westward inclined surfaces.

The most likely modern comparison is with the second order ridge and swale system which occurs on large submarine ridges. It is suggested that these too might, in some cases, be created by a combination of semi-permanent currents and occasional storms.


Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24