Clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern Andes

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Research Article| September 01, 1983 Clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern Andes MARGARET A. WINSLOW MARGARET A. WINSLOW 1Department of Earth and Planetary Sciences, City College of New York, New York, New York 10031; Lemont-Doherty Geological Observatory of Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1983) 94 (9): 1073–1080. https://doi.org/10.1130/0016-7606(1983)94<1073:CDSATS>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation MARGARET A. WINSLOW; Clastic dike swarms and the structural evolution of the foreland fold and thrust belt of the southern Andes. GSA Bulletin 1983;; 94 (9): 1073–1080. doi: https://doi.org/10.1130/0016-7606(1983)94<1073:CDSATS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Clastic dike swarms are intruded into a Cenozoic foreland fold and thrust belt in southern Chile. The dike material consists of sandstone and conglomerate with clasts as much as 25 cm in diameter. Brecciated wall rocks are also found in the clastic matrix. The dikes often exceed 50 cm in width and hundred? of metres in length in outcrop and are oriented overwhelmingly transverse to fold axes and parallel to cross joints. The dike swarms are concentrated near the “toe” of major thrusts, where they are found injected into the hanging wall.A regional axial planar spaced cleavage is developed in the clastic dikes and sills, clearly postdating injection of clastic material. Dike injection postdates at least the initiation of extension fractures (the cross-joint set). Within the swarms, the dike intrusions represent as much as 20% extension parallel to fold axes, in addition to several percent extension represented regionally by the cross joints. The structural features of the dike swarms and their geometric relationship to other structures suggest rapid, single-phase injection. The arrival of the front edge of a thrust on an already highly overpressured sedimentary sequence would cause an “instantaneous” increase in the overburden pressure and therefore could result in injection of a dense “slurry” of wet, coarse sediments along preexisting planes of weakness. Field relationships of mesoscopic structures suggest the following evolution: cross-joint development, incipient cleavage development, initiation of thrusting and buckling, clastic dike injection, regional spaced-cleavage development, and associated late-stage tightening of folds. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.