Eocene spiculites and spongolites in southwestern Australia: Not deep, not polar, but shallow and warm

Abstract

Research Article| September 01, 2000 Eocene spiculites and spongolites in southwestern Australia: Not deep, not polar, but shallow and warm Paul R. Gammon; Paul R. Gammon 1Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Noel P. James; Noel P. James 1Department of Geological Sciences, Queen's University, Kingston, Ontario K7L 3N6, Canada Search for other works by this author on: GSW Google Scholar Andrjez Pisera Andrjez Pisera 2Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, 00-818 Warsaw, Poland Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (9): 855–858. https://doi.org/10.1130/0091-7613(2000)28<855:ESASIS>2.0.CO;2 Article history received: 06 Jan 2000 rev-recd: 25 May 2000 accepted: 16 Jun 2000 first online: 02 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 Paul R. Gammon, Noel P. James, Andrjez Pisera; Eocene spiculites and spongolites in southwestern Australia: Not deep, not polar, but shallow and warm. Geology 2000;; 28 (9): 855–858. doi: https://doi.org/10.1130/0091-7613(2000)28<855:ESASIS>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 SocietyGeology Search Advanced Search Abstract Siliceous spongolite and spiculite are generally interpreted as deep- and/or cold-water deposits, largely because modern analogs are found mostly in cold- and/or deep-water environments. However, extensive shallow-water, biosiliceous accumulations are present in late Eocene age deposits of southern Western Australia. The attributes and paleoenvironmental setting of these accumulations frame the specific climatic and/or oceanographic constraints that allow such shallow neritic sediments to form. The generally fine grained siliciclastic-biosiliceous sediments accumulated in a nearshore, shallow-water setting, around numerous islands, and offshore from a warm-temperate, rainforest-covered upland. Sponges compose a lithistid-hexactinellid assemblage of Mesozoic Tethyan affinity, confined to deep water in the modern ocean, that migrated into neritic paleoenvironments during late Eocene time. Lithistids dominated shoreface environments and were reworked into sponge-conglomerate beaches, while hexactinellids flourished offshore in muddy subshoreface environments. These deposits also contain common soft demosponge spicules, and a rare but otherwise normal marine calcareous biota. The biosiliceous sediments grade offshore into bryozoan-rich marls and limestones. Sponges outcompeted the calcareous benthos in these inner shelf environments because of elevated amounts of land-derived nutrients that included high dissolved silica and a calm hydrodynamic setting. These deposits suggest that neither temperature nor water depth are critical factors for prolific sponge colonization. The rarity of such deposits in the rock record likely reflects the necessity for the coincidence of all of these factors, or they are misinterpreted. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.