In:
Solid Earth, Copernicus GmbH, Vol. 14, No. 4 ( 2023-04-05), p. 369-388
Abstract:
Abstract. The lateral distribution of strength within the crust is
non-uniform, dictated by crustal lithology and the presence and distribution
of heterogeneities within it. During continental extension, areas of crust
with distinct lithological and rheological properties manifest strain
differently, influencing the structural style, geometry, and evolution of the
developing rift system. Here, we use 3D thermo-mechanical models of
continental extension to explore how pre-rift upper-crustal strength
variations influence rift physiography. We model a 500×500×100 km volume
containing 125 km wide domains of mechanically “strong” and “weak” upper
crust along with two reference domains, based upon geological observations
of the Great South Basin, New Zealand, where extension occurs parallel to
the boundaries between distinct geological terranes. Crustal strength is
represented by varying the initial strength of 5 km3 blocks. Extension
is oriented parallel to the domain boundaries such that each domain is
subject to the same 5 mm yr−1 extension rate. Our modelling results show that
strain initially localises in the weak domain, with faults initially
following the distribution of initial plastic strain before reorganising to
produce a well-established network, all occurring in the initial 100 kyr. In contrast, little to no localisation occurs in the strong
domain, which is characterised by uniform strain. We find that although
faults in the weak domain are initially inhibited at the terrane boundaries,
they eventually propagate through and “seed” faults in the relatively
strong adjacent domains. We show characteristic structural styles
associated with strong and weak crust and relate our observations to
rift systems developed across laterally heterogeneous crust worldwide, such
as the Great South Basin, New Zealand, and the Tanganyika Rift, East Africa.
Type of Medium:
Online Resource
ISSN:
1869-9529
DOI:
10.5194/se-14-369-2023
DOI:
10.5194/se-14-369-2023-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2023
detail.hit.zdb_id:
2545676-3
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