A 'flash-flood' dominated braid delta in the upper Proterozoic Næringselva Member, Varanger Peninsula, northern Norway
pp. 63-80

The upper part of the upper Proterozoic Næringselva Member comprises sharply based sandstone bodies, 7-35 m thick, interpreted as distributary channel deposits. In contrast to most modem and ancient counterparts, these channel deposits are dominated by upper-flow regime, planar stratification and sigmoidal cross-stratification. This is related to the absence of vegetation during the Precambrian and the 'flash-flood' nature of the depositional system. Sharply based, distributary channel sandstone bodies in the Seglodden area are separated by finer grained units comprising coarsening upward facies sequences interpreted as bay-fill deposits, in the form of sheet-flood dominated and 'Gilbert' type minor mouth bars. Bay-fill deposits are not observed in the Smellror area, where delta-front deposits are more prominent, comprising coarsening upward mouth-bar deposits 15-20 m thick. Owing to the dominance of river-current-generated sedimentary structures within bay-fill and delta-front deposits, it is suggested that the studied section of the Næringselva Member formed part of a fluvially dominated delta that prograded eastwards into a low-energy, protected basin, possibly with a related eastwards deepening of the delta-front setting.

Andor Hjellbakk, Fina Exploration Norway. Present address: Esso Norge AS, P.O. Box 60, N-4033 Forus, Norway.