The Tertiary fold-thrust belt
in Oscar II Land, central Spitsbergen, consists of three major zones of
distinct structural style: (1) a western basement-involved fold-thrust
complex, (2) a central zone of thin-skinned fold-thrust units above a decollement
in Permian evaporites, and (3) an eastern zone characterized by a frontal
duplex system in the fold-thrust belt, bounded eastward by steep, basement-rooted
reverse faults (Billefjorden and Lomfjorden fault zones) beneath subhorizontal
platform strata. Offshore seismic data from Isfjorden (Statoil) confirm
the threefold zonation and document thick-skinned and thin-skinned structural
interactions in both the fold-thrust belt and the foreland section. An
admissible cross section yields about 45%, or 20 km, of shortening in Oscar
II Land. Deeper parts of the seismic profiles show fault-bounded Devonian
(central and east) and Carboniferous (west) basins. The structural grain
of the Tertiary fold-thrust belt partly coincides with the margin-bounding
normal faults of these basins, suggesting that preexisting structures and
stratigraphy controlled the Tertiary fold-thrust belt development.
A kinematic evolution of the fold-thrust
belt is invoked: (1) north-northeast-directed, bedding-
parallel shortening, (2) major west-southwest-east-northeast
shortening, with in-sequence foreland fold-thrust propagation, (3) basement-involved,
1997. The American Association of Petroleum Geologists. All rights reserved.
received October 30, 1995; revised manuscript received June 5, 1996; final
acceptance October 28, 1996.
of Biology and Geology, University of Tromsø, N-9037 Tromsø,
Survey of Norway, P.O. Box 3006, N-7002 Trondheim, Norway.
of Geology, University of Oslo, P.O. Box 1047, N-0316, Oslo, Norway.
work for this project was funded through the University of Tromsø,
University of Oslo, RNF/NAVF (grant 440.92/057), VISTA-Statoil, Norwegian
Petroleum Directorate, and Norsk Hydro/SNSK. We thank Statoil for access
to seismic lines from Isfjorden, and the Norwegian Polar Institute for
logistical support. K. Kleinspehn, R. Gries, and J. D. Lowell are acknowledged
for fruitful review of the manuscript.