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The AAPG/Datapages Combined Publications Database

CSPG Special Publications

Abstract


Sedimentology of Gravels and Conglomerates — Memoir 10, 1984
Pages 359-382
Ancient Submarine Slope-Fan Systems

Fan-Delta to Submarine Fan Conglomerates of the Volgian-Valanginian Wollaston Forland Group, East Greenland

Finn Surlyk

Abstract

A major episode of block faulting and tilting occurred in East Greenland roughly at the Jurassic-Cretaceous boundary. In northern East Greenland an up to 3 km thick syntectonic wedge constituting the Wollaston Forland Group was deposited during Middle Volgian to Valanginian time. The group was formed as a coalescent fringe of fan-deltas - submarine fans along a major scarp on tilted blocks. Water depth ranged from zero at the scarp to about 1 km at the basin axis, 15 km east of and parallel to the scarp. The fan sediments are coarse conglomerates, pebbly and coarse sandstones deposited from sediment gravity flows. The flow types include rock-fall avalanches, retrogressive flow slides, sandy debris flows, density modified grain flows, gravelly high-density turbidity currents sometimes transitional to liquefied flows, and low-density turbidity currents. Over 15 km from the scarp to the basin axis there is no downslope change in conglomerate facies types or in the relative proportion. These observations are incompatible with the predicted downslope changes in published conglomerate models. It is shown that there is no unequivocal correlation between proximality (defined as distance from source or fan apex) and travel distance of flows for the Wollaston Forland conglomerates. Furthermore, several of the features used to define the models appear to reflect mechanisms active during deposition rather than transportation. This means that the models only to some extent reflect a succession of stages in flow maturity. The observed contrast between theory and observation can thus easily be accounted for and the Wollaston Forland conglomerates may represent the rule rather than the exception. In this case the use of the published conglomerate models in basin analysis should be discontinued.


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