Abstract
Abstract. Compressional strains may manifest along pre-existing
structures within the lithosphere, far from the plate boundaries along which
the causal stress is greatest. The style and magnitude of the related
contraction is expressed in different ways, depending on the geometric and
mechanical properties of the pre-existing structure. A three-dimensional
approach is thus required to understand how compression may be partitioned
and expressed along structures in space and time. We here examine how
post-rift compressional strains are expressed along the northern margin of
the Farsund Basin during Late Cretaceous inversion and Palaeogene–Neogene
pulses of uplift. At the largest scale, stress localises along the
lithosphere-scale Sorgenfrei-Tornquist Zone, where it is expressed in the
upper crust as hangingwall folding, reverse reactivation of the
basin-bounding normal fault, and bulk regional uplift. The geometry of the
northern margin of the basin varies along strike, with a normal fault system
passing eastward into an unfaulted ramp. Late Cretaceous compressive
stresses, originating from the convergence between Africa, Iberia, and
Europe, selectively reactivated geometrically simple, planar sections of the
fault, producing hangingwall anticlines and causing long-wavelength folding
of the basin fill. The amplitude of these anticlines decreases upwards due
to tightening of pre-existing fault propagation folds at greater depths. In
contrast, later Palaeogene–Neogene uplift is accommodated by long-wavelength
folding and regional uplift of the entire basin. Subcrop mapping below a
major, uplift-related unconformity and borehole-based compaction analysis
show that uplift increases to the north and east, with the
Sorgenfrei-Tornquist Zone representing a hinge line rather than a focal point
to uplift, as was the case during earlier Late Cretaceous compression. We
show how compressional stresses may be accommodated by different mechanisms
within structurally complex settings. Furthermore, the prior history of a
structure may also influence the mechanism and structural style of
shortening that it experiences.
Subject
Paleontology,Stratigraphy,Earth-Surface Processes,Geochemistry and Petrology,Geology,Geophysics,Soil Science
Cited by
15 articles.
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