(1) Padova University, Padova, Italy
(2) University of Wyoming, Laramie, WY
ABSTRACT: Linkage between Shelf-Edge Valleys and Upper Slope Canyons, Eocene, Spitsbergen
The Battfjellet Formation (Eocene) on Spitsbergen consists of spectacularly exposed coastal plain-shelf-basin floor clinoforms up to 350m in amplitude. Although most slope profiles are shaly, the mountainside Brogniartfjellet has a series of sand-prone clinoforms that show a near-horizontal, shelf-edge migration trajectory. Two of these clinoforms, showing small upper-slope canyons that link back to outer-shelf incised valleys, have been documented by walk-out.
The small upper-slope canyons, originated from retrogressive slump scars, are up to 25m deep and merge at the shelf break into river-cut incised valleys. The shelf segment of the clinothems is up to 10 km long, and supports 30m-thick, highstand-to-forced regressive shelf-edge deltas. The delta topsets are deeply incised by fluvial surfaces of erosion that are up to 12 m deep and paved by shale rip-up conglomerates. The infill is dominated by 1-3m-thick, flat and low-angle laminated, medium-grained sandstone beds deposited from upper-flow regime conditions in river-channels. Successive pulses of forced regressive erosion can be demonstrated, separated by minor re-establishment of delta-front facies. At lowstand, shelf incision reached the shelf break allowing the river system to feed sediment directly into the small canyons that became the conduits to the basin floor. The canyon fills show repeated phases of erosion and by pass, alternating with low-efficient, hyperpycnal flow deposits, and have an architecture of basinward-stepping. At the transgressive stage the canyons were blanketed by mud, there was tidal re-working at the shelf edge, and the establishment of a tidal-dominated estuary.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado