Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts

Abstract

Research Article| February 01, 2008 Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts C.M. Reid; C.M. Reid 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar N.P. James; N.P. James 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar T.K. Kyser; T.K. Kyser 1Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar N. Barrett; N. Barrett 2Tasmanian Aquaculture & Fisheries Institute (TAFI), University of Tasmania, Private Bag 49, Hobart, Tasmania 7000, Australia Search for other works by this author on: GSW Google Scholar A.J. Hirst A.J. Hirst 2Tasmanian Aquaculture & Fisheries Institute (TAFI), University of Tasmania, Private Bag 49, Hobart, Tasmania 7000, Australia Search for other works by this author on: GSW Google Scholar Geology (2008) 36 (2): 107–110. https://doi.org/10.1130/G24333A.1 Article history received: 04 Aug 2007 rev-recd: 23 Sep 2007 accepted: 25 Sep 2007 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation C.M. Reid, N.P. James, T.K. Kyser, N. Barrett, A.J. Hirst; Modern estuarine siliceous spiculites, Tasmania, Australia: A non-polar link to Phanerozoic spiculitic cherts. Geology 2008;; 36 (2): 107–110. doi: https://doi.org/10.1130/G24333A.1 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 SocietyGeology Search Advanced Search Abstract Biosiliceous sedimentary rocks are well known from the geologic record and many are correctly interpreted to have formed in deep-water or cold-water environments. Shallow non-polar spiculites are also known from the rock record, yet no modern analog has been documented for such environments. Bathurst Harbour, an estuarine system in southwest Tasmania, provides this much-needed modern analog. In this system a sharp halocline separates tannin-rich low-salinity surface waters from clear marine bottom waters. Tannins supply few nutrients and substantially reduce light penetration to bottom environments, resulting in a thinned photic zone and the mixing of deeper-water sub-photic biotas of soft corals, bryozoans, and sponges with other organisms more typical of this temperate shallow-water environment. The well-defined halocline allows a typically marine biota, including echinoderms, to live in bottom waters of this estuarine setting. The bioclastic factory, producing both carbonate and siliceous particles, exists in marine subphotic bottom waters of incised channel and shallow rocky environments along the shoreline. Extensive organic-rich soft sediments in protected embayments generate few bioclasts, but contain allochthonous sponge spicules transported from the adjacent bioclastic factory. Trapping of organic material within the estuarine system lowers sediment pH and promotes dissolution of carbonate biofragments, resulting in preferential preservation of siliceous sponge spicules. This situation implies that many biosiliceous neritic deposits in the rock record may be the result of similar preferential preservation. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.