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Piret Plink-Bjorklund1, Ron Steel1
(1) Wyoming University, Laramie, WY

Abstract: Evidence of Falling and Rising Relative Sealevel, Seen in Architecture of a Thick Slope-Sand Accumulation

Högsnyta slope accumulation is a 70m-thick and 2500m-long sand complex, Central Tertiary Basin, Spitsbergen. The unusually good exposures enable detailed documentation of depositional architecture from shelf-edge to basin-floor. Five sequence stratigraphic compartments in the body reflect a changing relative sealevel history. Compartment 1 contains shelf-edge deltas that prograded onto the upper slope. Compartments 2 and 3 contain an upper-slope channelled turbidite complex and a middle-slope lobate turbidite complex. In compartment 2 the downward depositional trajectory, 2 major erosion surfaces, strong basinward shift of depositional units and high frequency of channels evidence a falling relative sealevel. The channels are filled during intermittent floodings. The most prominent erosion surface generated by the relative sealevel fall is an unconformity at the top of compartment 2 that changes into a correlative conformity on the middle slope. In compartment 3 depositional units onlap landwards onto the unconformity evidencing a rising relative sealevel. The uppermost depositional unit floods back onto the shelf-edge. Compartment 4 contains several progradational to backstepping depositional units that contain shelf-edge deltas, and upper- to middle-slope turbidites. This compartment reflect a rising relative sealevel, seen by general aggradational to backstepping character, lack of erosion surfaces, very low frequency of channels and a major flooding onto shelf-edge at the top of the compartment. Compartment 5 is a progradational complex of upper- to middle-slope turbidites with a channelled level at the top. Compartments 4 and 5 contain significantly thicker depositional units compared to compartments 2 and 3. The whole succession is flooded by maine shales.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana