T77 Deformation Zones in Time and Space I: A Celebration of the Career of Steven Wojtal

Monday, 10 October 2022
8:00 AM - 12:00 PM
207

KINEMATIC PARTITIONING IN THE ECHO LAKE DEFORMATION ZONE, SEIAD ULTRAMAFIC COMPLEX, KLAMATH MOUNTAINS, CA

Paper number: T77-13
Program: Technical Sessions
Time: 10:55 AM – 11:10 AM

Authors

Abstract

The Echo Lake deformation zone (ELDZ) is a >60 m-thick lithologically diverse shear zone. The ELDZ is situated between two amphibolite- to granulite-facies peridotite bodies in the Seiad ultramafic complex in the Rattlesnake Creek Terrane, which is an oceanic crust and mantle mélange located in the Klamath Mountains Province, northwestern California and southwestern Oregon. Tectonites in the ELDZ include metasedimentary rocks (marble, quartzite, and quartz-rich schist) and peridotites (dunite, harzburgite, and lherzolite) which share a planar fabric that crosscuts adjacent rocks in the complex. Mineral stretching lineations are well-developed across the ELDZ and exhibit a preferred NW-plunging orientation, compatible with previous kinematic investigations that inferred either top-to-NW or top-to-SE shear sense. Conversely, the directions of kinematic indicators and local vorticity axes vary across the zone and within units. Vorticity axis patterns in the metasedimentary rocks include foliation-parallel girdles, lineation-parallel maxima, and lineation-perpendicular maxima, whereas vorticity axes in the peridotites define an elongated-maxima pattern (partially girdled). Compared to vorticity axes measured in deformation experiments with different geometries (simple shear, compression, tension, and transpression), patterns observed in ELDZ tectonites suggest mesoscopic kinematic partitioning and reveal a larger-scale transpressional kinematic regime related to Middle Jurassic regional contraction and juxtaposition of the Rattlesnake Creek and Western Hayfork terranes.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-382804

© Copyright 2022 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.