The details of subduction zone locking place constraints on the characteristics of megathrust events. Due to the lack of significant present‐day seismicity along the Cascadia subduction interface, geodetic data are used to assess subduction locking along the margin. We isolate the subduction signal from other tectonic signals within the Cascadia GPS field, to assess the details of plate‐interface locking. Apparent coupling determined by a simple homogenous elastic half‐space inversion cannot everywhere reproduce the subduction component of the GPS field. Consequently, we explore the relationships among upper‐plate strength, locking depth and the resulting surface velocity signal using 2D finite element models. When the upper plate is composed of a weak material, trenchward of a strong backstop, we find that the down‐dip limit of locking relative to the location of the weak‐to‐strong transition controls how upper‐plate deformation is spatially distributed. If locking extends into the stronger material, as observed in central Cascadia, the surface velocity field propagates farther inland than expected from a simple homogeneous elastic model. In contrast, in southern Cascadia, because locking terminates within the weak accretionary margin, upper‐plate shortening is localized within the weaker material, particularly in the region between the end of locking and the strong Klamath terrane. This behavior provides a possible mechanism for producing the high (geodetic and permanent) uplift rates, plate‐motion‐parallel shortening, and crustal exhumation observed in many active and fossil subduction zones.
- Award ID(s):
- 1633831
- NSF-PAR ID:
- 10113100
- Date Published:
- Journal Name:
- Hydrobiologia
- Volume:
- 830
- Issue:
- 1
- ISSN:
- 0018-8158
- Page Range / eLocation ID:
- 93 to 113
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Cistecephalids are among the most distinctive Permian dicynodonts because of their highly derived skulls and postcrania, which indicate a fossorial ecology. Four cistecephalid species have been described from India, South Africa, and Tanzania; a fifth putative species has been reported from the Luangwa Basin of Zambia but never formally described. Here we present a detailed description of the Luangwa Basin cistecephalid, which we name
Kembawacela kitchingi gen. et. sp. nov. The most obvious diagnostic character ofK. kitchingi is the presence of caniniform tusks in most specimens. Other important characters include a pineal foramen located at the posterior end of the skull roof; an interparietal that has a pair of anterior processes that extend onto the dorsal surface of the skull, flanking the pineal foramen (but otherwise is restricted to the occipital surface); an undivided nuchal crest; and a trough on the ventral surface of the mid‐ventral vomerine plate. Phylogenetic analysis reconstructsKembawacela as a basal cistecephalid and confirms that Cistecephalidae is a well‐supported clade. However, relationships within the clade received low branch support. Increased knowledge of cistecephalid diversity shows that they vary in functionally relevant characters, such as degree of inflation of the bony vestibule and the morphology of the scapula and humerus, indicating the need for a more nuanced approach to the relationship between form, function and ecology in the clade. The highly allopatric distribution of cistecephalid species suggests that they experienced strong interspecific competition for limited resources and had limited dispersal ability, similar to extant subterranean mammals.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/s10750-018-3857-8
