Jeff P. Crabaugh1
(1) University of Wyoming, Laramie, WY
Abstract: Facies architecture and stratigraphy of basin-floor fan systems: Central Tertiary Basin, (Eocene) Spitsbergen
The Central Tertiary Basin of Spitsbergen displays Eocene shelf-to-slope-to-basin floor clinothems along mountainside exposures. Outcrops at a scale of 100's of meters in height and 10 kilometers in length located along the margins of Van Keulenfjord reveal the progradational stacking of these clinothems. The progradational stacking reflects depocenter migration which was controlled by time-equivalent overthrusting in the West Spitsbergen Orogenic Belt. The degree of exposure and the delineation of clinoform geometry allow a clear distinction to be made between slope and basin-floor environments. Three submarine-fan systems (50 to 100m in composite thickness) lie at the basinward-edge of the prograding clinoforms exposed near the head of the modern-day fjord.
Architectural analysis of individual fan-systems reveals the following relationships. The basin-floor fan systems are characterized by a vertical succession of rippled to parallel-laminated thin-beds interbedded with structureless thick-bedded units low in the succession, which changes progressively upwards to structureless and soft-sediment deformed, very thick-bedded units. Intervals dominated by thin-bedded units display sediment-transport features (i.e., sole marks) indicating the predominant paleoflow contained a strong component oriented approximately parallel to the down-slope direction. Intervals characterized by very thick-beds display sole marks indicating the dominant paleoflow was roughly parallel to an along-slope direction. Thus, vertical facies trends within individual fan-systems point to a temporal evolution in which axial transport eventually dominates over down-slope transport. Progradational stacking of successively younger fan-systems results in an upward progression of basin-floor to slope environments.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana