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

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Abstract

The Klamath Mountains state of northwestern Californiaa€“southwestern Oregon is an anomalous take into account the Cascadia margin; these mountains possess highest typical topography, the eldest rocks, together with only determined instance of later part of the Cenozoic detachment faulting from inside the coastal mountains of the Cascadia forearc. Low-temperature thermochronology (apatite fission-track, apatite [U-Th]/He) analyses through the central and southern Klamath Mountains state record two distinct exhumation events-a Cretaceousa€“Paleocene regional cooling and a southward-migrating locus of rapid cooling/exhumation in the middle Tertiary. We infer this particular pattern reflects two distinct steps of exhumation: regional surface erosion (older) and migrating localized tectonic exhumation (younger). At the south maximum for this area for rapid air conditioning, slickenside striations on exposed La Grange error surface record southward displacement regarding the higher plate along a shallowly dipping (a??20A°) detachment surface. Thermochronologic data constrain typical dip on the mistake to a couple grade, upper-plate depth to

INTRODUCTION

The Klamath Mountain state (Fig. 1) straddles significant change when you look at the America dish boundary from subduction along Cascadia to translation across the San Andreas system, as well as being both geologically and topographically distinctive. The orogen’s Neogene to Holocene tectonic background potentially provides a window in to the progression associated with dish border as it underwent the changeover from a long reputation for subduction (Farallon, Juan de Fuca) to encroaching translational (Pacific) dish interactions. The Klamath Mountain state currently hosts many of the highest geography along side convergent border (Fig. 1A). Maximum and mean elevations into the Klamath Mountains is greater than those someplace else within the seaside sugar daddy uk range of Cascadia (Kelsey et al., 1994), and the Klamath hill state, consisting of Precambrian to Late Cretaceous, primarily oceanic tectonostratigraphic terranes, include the eldest (Wallin et al., 1995) and extremely structurally complex (cf. Irwin, 1981, 1985) products along the Cascadia margin. The time scale when this high geography produced while the commitment between uplift and exhumation of Paleozoic and Mesozoic bedrock stay uncertain.

Productive deformation in southernmost Cascadia subduction region, at the latitude associated with the Klamath hills province, also differs from that of other Cascadia margin.

Designs of seismicity, like the spatial and temporary submission 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 area earthquake record (age.g., Wang et al., 2013), all separate the southern the main Cascadia subduction region.

(1) really does the Klamath topographic massif reflect relict (later Cretaceousa€“Early Tertiary) topography, or perhaps is it a result of youthful and/or ongoing uplift linked to the modern dish border?

(2) perform the distinct seismologic faculties from the southernmost Cascadia subduction region margin mirror the geologic character of regional forearc (elizabeth.g., crust in the Klamath Mountain province), or will they be merely a purpose of the existing plate-tectonic style separate of upper-plate crustal structure?

Within this papers, we present newer low-temperature thermochronologic data from central and southeastern Klamath hills, use these to constrain the motion reputation of a regionally considerable error (the La Grange fault), and read their own implications for your Cenozoic tectonic development for the Klamath Mountains province. With brand new thermochronometry facts, we testing earlier interpretations of Cenozoic reputation for the Klamath area, e.g., Neogene Condrey Mountain dome (Mortimer and Coleman, 1985) and Klamath peneplain (Diller, 1902; Aalto, 2006). We subsequently discuss the spatial and temporary communication between mid-Cenozoic tectonic happenings in Klamath Mountains state while the accretion from the Siletz terrane inside the Oregon coastline selections (Wells et al., 2014). We consider that Cenozoic tectonism inside the Klamath hills state was actually linked to events regarding the Cascadia margin with the north.