Limestone and chert in tectonic blocks from the Esk Head subterrane, South Island, New Zealand

Abstract

Research Article| August 01, 1988 Limestone and chert in tectonic blocks from the Esk Head subterrane, South Island, New Zealand N. J. SILBERLING; N. J. SILBERLING 1US Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar K. M. NICHOLS; K. M. NICHOLS 1US Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar J. D. BRADSHAW; J. D. BRADSHAW 2Department of Geology, University of Canterbury, Christchurch 1, New Zealand Search for other works by this author on: GSW Google Scholar C. D. BLOME C. D. BLOME 1US Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1988) 100 (8): 1213–1223. https://doi.org/10.1130/0016-7606(1988)100<1213:LACITB>2.3.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 N. J. SILBERLING, K. M. NICHOLS, J. D. BRADSHAW, C. D. BLOME; Limestone and chert in tectonic blocks from the Esk Head subterrane, South Island, New Zealand. GSA Bulletin 1988;; 100 (8): 1213–1223. doi: https://doi.org/10.1130/0016-7606(1988)100<1213:LACITB>2.3.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 The Esk Head subterrane is a continuous belt, generally 10-20 km wide, of tectonic mélange and broken formation on the South Island of New Zealand. This subterrane separates older and younger parts of the Torlesse terrane which is an extensive accretionary prism composed mostly of quartzo-feldspathic, submarine-fan deposits ranging from Permian to Early Cretaceous in age. The Torlesse is the most Pacific-ward of several Permian and Mesozoic accreted terranes in New Zealand that record tectonic amalgamation and ultimate accretion against the Pacific-facing Gondwana margin. The Esk Head subterrane of the Torlesse is especially informative because it includes within it conspicuous tectonic blocks of submarine basalt and a variety of basalt-associated seamount and sea-floor limestones and cherty rocks thought to be representative of the subducted plate. Limestones in tectonic blocks are of Late Triassic and probably Jurassic ages and include (1) submarine-cemented, pelagic-bivalve, geopetal packstone-grainstone; (2) brachiopod-bryozoan encrinite; and (3) radiolarian, pelagic lime mudstone. Most of the Triassic blocks have been dated using conodonts which have remarkably low color alteration index (CAI) values (<1.5). An incomplete sampling of cherts in tectonic blocks and from Holocene gravels derived from the Esk Head subterrane yields radiolarian-based ages of Late Triassic, Early Jurassic, Middle Jurassic, and Late Jurassic.Paleogeographic inferences drawn from megafossils, bioclasts, and radiolarians, as well as from carbonate cements, indicate deposition of the oceanic sedimentary rocks at paleolatitudes somewhat lower than that of the New Zealand part of the Gondwana margin, but higher than paleoequatorial latitudes. These oceanic sediments and their basaltic substrates were evidently emplaced in the Torlesse accretionary prism following off-scraping from an extensive subducting oceanic plate, probably the Phoenix plate, which was obliquely convergent with the northwest-trending Gondwana margin during Late Jurassic and/or Early Cretaceous time. 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.