This young celebration try localized inside the geographic level for the Los Angeles Grange error

Rachel Piotraschke, Susan M. Cashman, Kevin P. Furlong, Peter J.J. Kamp, elizabeth they on Siletzia?. Lithosphere 2015;; 7 (4): 427a€“440. doi:

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Abstract

The Klamath Mountains state of northwestern Californiaa€“southwestern Oregon are an anomalous take into account the Cascadia margin; these mountains experience the finest medium topography, the oldest rocks, while the just identified instance of late Cenozoic detachment faulting when you look at the seaside mountains with the Cascadia forearc. Low-temperature thermochronology (apatite fission-track, apatite [U-Th]/He) analyses from main and south Klamath hills province record two distinct exhumation events-a Cretaceousa€“Paleocene regional cooling and a southward-migrating locus of fast cooling/exhumation in the middle Tertiary. We infer that pattern reflects two unique steps of exhumation: local exterior erosion (older) and moving localized tectonic exhumation (younger). At southern limitation with this area for rapid cooling, slickenside striations on the revealed Los Angeles Grange fault surface record southward displacement in the top plate along a shallowly dipping (a??20A°) detachment surface. Thermochronologic information constrain typical plunge on the fault to a couple grade, upper-plate width to

INTRODUCTION

The Klamath Mountain state (Fig. 1) straddles significant changeover inside the North America plate border from subduction along Cascadia to translation along the San Andreas system, and is both geologically and topographically distinct. The orogen’s Neogene to Holocene tectonic records probably produces a window to the progression for the plate border because it underwent the change from an extended history of subduction (Farallon, Juan de Fuca) to encroaching translational (Pacific) plate communications. The Klamath Mountain state at present has a few of the greatest geography along the convergent boundary (Fig. 1A). Maximum and imply elevations into the Klamath hills were greater than those someplace else when you look at the coastal ranges of Cascadia (Kelsey et al., 1994), plus the Klamath hill state, consisting of Precambrian to Late Cretaceous, mainly oceanic tectonostratigraphic terranes, consists of the oldest (Wallin et al., 1995) and one of the most structurally intricate (cf. Irwin, 1981, 1985) units across the Cascadia margin. The time where this high topography developed plus the connection between uplift and exhumation of Paleozoic and Mesozoic bedrock remain unclear.

Productive deformation in southernmost Cascadia subduction area, at latitude from the Klamath hills province, in addition varies from compared to other Cascadia margin.

Designs of seismicity, including the spatial and temporary distribution of episodic tremor and slide occasions (Fig. 1A; Szeliga et al., 2004; Brudzinski and Allen, 2007; Gomberg et al., 2010; K. Creager, , individual commun.), anticorrelation of tremor and little upper-plate earthquakes (Boyarko and Brudzinski, 2010; Gomberg et al., 2010), and inferred segmentation of Cascadia subduction zone earthquake records (e.g., Wang et al., 2013), all recognize the south part of the Cascadia subduction area.

(1) do the Klamath topographic massif echo relict (later Cretaceousa€“Early Tertiary) topography, or perhaps is it a direct result young and/or ongoing uplift for this contemporary dish border?

(2) carry out the unique seismologic faculties from the southernmost Cascadia subduction area margin mirror the geologic personality of this local forearc (elizabeth.g., crust from the Klamath hill state), or will they be merely a function of the existing plate-tectonic setting separate of upper-plate crustal framework?

In this report, we found newer low-temperature thermochronologic facts from central and southeastern Klamath hills, make use of these to constrain the movement reputation of a regionally significant failing (the Los Angeles Grange mistake), and read their unique ramifications when it comes down to Cenozoic tectonic advancement regarding the Klamath Mountains state. With newer thermochronometry data, we testing earlier interpretations of Cenozoic history of the Klamath region, e.g., Neogene Condrey Mountain dome (Mortimer and Coleman, men looking women 1985) and Klamath peneplain (Diller, 1902; Aalto, 2006). We after that talk about the spatial and temporal communication between mid-Cenozoic tectonic activities when you look at the Klamath Mountains state together with accretion from the Siletz terrane when you look at the Oregon coastline selections (Wells et al., 2014). We deduce that Cenozoic tectonism during the Klamath Mountains province had been connected to events from the Cascadia margin to the north.