Puente Hills Blind-Thrust System, Los Angeles, California

2002 ◽  
Vol 92 (8) ◽  
pp. 2946-2960 ◽  
Author(s):  
J. H. Shaw
Keyword(s):  
Los Angeles ◽  
Blind Thrust ◽  
Thrust System

scholarly journals Hillslope denudation and morphologic response to a rock uplift gradient

2020 ◽  
Vol 8 (2) ◽  
pp. 221-243 ◽  
Author(s):  
Vincent Godard ◽  
Jean-Claude Hippolyte ◽  
Edward Cushing ◽  
Nicolas Espurt ◽  
Jules Fleury ◽  
...  
Keyword(s):  
High Resolution ◽  
Strong Dependence ◽  
Digital Terrain Model ◽  
Slip Rate ◽  
Joint Analysis ◽  
Deformation Model ◽  
Base Level ◽  
Denudation Rates ◽  
Blind Thrust ◽  
Thrust System

Abstract. Documenting the spatial variability of tectonic processes from topography is routinely undertaken through the analysis of river profiles, since a direct relationship between fluvial gradient and rock uplift has been identified by incision models. Similarly, theoretical formulations of hillslope profiles predict a strong dependence on their base-level lowering rate, which in most situations is set by channel incision. However, the reduced sensitivity of near-threshold hillslopes and the limited availability of high-resolution topographic data has often been a major limitation for their use to investigate tectonic gradients. Here we combined high-resolution analysis of hillslope morphology and cosmogenic-nuclide-derived denudation rates to unravel the distribution of rock uplift across a blind thrust system at the southwestern Alpine front in France. Our study is located in the Mio-Pliocene Valensole molassic basin, where a series of folds and thrusts has deformed a plateau surface. We focused on a series of catchments aligned perpendicular to the main structures. Using a 1 m lidar digital terrain model, we extracted hillslope topographic properties such as hilltop curvature CHT and nondimensional erosion rates E∗. We observed systematic variation of these metrics coincident with the location of a major underlying thrust system identified by seismic surveys. Using a simple deformation model, the inversion of the E∗ pattern allows us to propose a location and dip for a blind thrust, which are consistent with available geological and geophysical data. We also sampled clasts from eroding conglomerates at several hilltop locations for 10Be and 26Al concentration measurements. Calculated hilltop denudation rates range from 40 to 120 mm kyr−1. These denudation rates appear to be correlated with E∗ and CHT that were extracted from the morphological analysis, and these rates are used to derive absolute estimates for the fault slip rate. This high-resolution hillslope analysis allows us to resolve short-wavelength variations in rock uplift that would not be possible to unravel using commonly used channel-profile-based methods. Our joint analysis of topography and geochronological data supports the interpretation of active thrusting at the southwestern Alpine front, and such approaches may bring crucial complementary constraints to morphotectonic analysis for the study of slowly slipping faults.

scholarly journals Control of Permian and Triassic faults on Alpine basement deformation in the Argentera massif (external southern French Alps)

2003 ◽  
Vol 174 (5) ◽  
pp. 481-496 ◽  
Author(s):  
Jean Delteil ◽  
Jean-François Stephan ◽  
Mikaël Attal
Keyword(s):  
Sedimentary Cover ◽  
Lower Triassic ◽  
Structural Investigations ◽  
French Alps ◽  
Blind Thrust ◽  
Thrust System ◽  
Block Pattern ◽  
Heterogeneous Deformation ◽  
Basement Deformation ◽  
Compressional Strain

Abstract Structural investigations reveal intense and heterogeneous deformation of the sedimentary cover attached to the basement complex of the southern Argentera and Barrot massifs (southernmost External Basement Massifs of the French Alps). Permian and early Triassic syn-depositional extensional tectonics imparted a tilted block pattern to the massifs. An early Miocene first stage of Alpine compression caused pervasive cleavage. This cleavage was controlled by the former pre-existing faults but is nevertheless consistent with NNE contraction. Where regional shortening is orthogonal to the trend of pre-existing faults the pervasive deformation produced either irrotational compressional strain (where no fault inversion occurred), or rotational compressional strain involving syn-cleavage shearing (where faults with favorable paleo-dip were inverted). Where the shortening direction is oblique to the paleo-fault trends, a component of strike-slip movement may locally prevail. A 22 %, N020o directed horizontal shortening, of 11 km, has been calculated based on deformed sedimentary markers in the Permian series and parallel folds in Lower Triassic quartzite. A shallower deformation as brittle reverse faults postdates the cleavage at the southwestern tip of the Argentera Massif and accounts for 4 km of extra shortening. Both types of deformation are connected at depth to a crustal blind thrust system and the Argentera Massif is over-thrust to the south-southwest. The observed strain indicates the Argentera Massif area underwent, from earliest Miocene to Present, a NNE to N rotating compression at distance from the left-lateral southwestern boundary of the Adria block.

scholarly journals Shallow seismic imaging of folds above the Puente Hills blind-thrust fault, Los Angeles, California

2002 ◽  
Vol 29 (9) ◽  
pp. 18-1-18-4 ◽  
Author(s):  
Thomas L. Pratt ◽  
John H. Shaw ◽  
James F. Dolan ◽  
Shari A. Christofferson ◽  
Robert A. Williams ◽  
...  
Keyword(s):  
Los Angeles ◽  
Seismic Imaging ◽  
Thrust Fault ◽  
Shallow Seismic ◽  
Blind Thrust ◽  
Blind Thrust Fault
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