Facies Architecture and Stratigraphy of a Deltaic-Detached Turbidite System in the Eocene of Svalbard (Norwegian Artic)
MELLERE, D., E. GRANBERO, S. JOHANSEN, and T. OLSEN
The Eocene Battfjellet Formation in Central Spitsbergen consists of a series
of steeply dipping deltaic clinoforms which prograde into basinal shales. One of
these apparently uniform sandy clinoforms has been mapped in detail, walking-out
facies relationships and bounding surfaces. The tongue is up to 60 m thick, and
crops out in a 6 km long, continuous dip-oriented exposure in Van Keulenfjord.
The tongue shows a complex four-tiered internal architecture with superimposed,
deltaic and turbidite sandbodies. In its landward reaches, the lower part of the
tongue consists of a 50 m thick, coarsening-upward mouth bar complexes and
fluvial distributary channels of highstand origin which rapidly pro grade onto
the slope and thin basinwards into prodelta turbidites. A surface of erosion and
by-pass separates this first unit from some 20 m thick, lowstand sandy turbidite
wedge which develops at the base of slope into the basin floor. The wedge
consists of heterolithic slumped deposits sharply overlain by sandy
channel-levees and lobate sheets of high-density turbidites. After an initial
stage of progradation, the turbidite system retrogrades, onlapping the slope and
developing a 13 m thick shale-prone wedge of heterolithic channel/levees which
pinch out at the shelf break. The upper part of the tongue shows the
progradation and then the retrogradation of another river-dominated deltaic
system which downlaps the slope turbidite wedge. The sandy and the heterolithic
turbidite wedges (both detached from the underlying delta system) and the
overlying delta are believed to have been deposited all during lowstand and,
limitatively to the uppermost deltaic complex, during the initial stage of
transgression. The tongue is marked at its top by a maximum flooding surface and
by the downlap of the overlying deltaic shaley clinoforms.