Early Proterozoic ice-proximal glaciomarine deposition: The lower Gowganda Formation at Cobalt, Ontario, Canada

Abstract

Research Article| April 01, 1987 Early Proterozoic ice-proximal glaciomarine deposition: The lower Gowganda Formation at Cobalt, Ontario, Canada P. S. MUSTARD; P. S. MUSTARD 1Department of Geology, Carleton University, Ottawa, Ontario, Canada K1S 5B6 Search for other works by this author on: GSW Google Scholar J. A. DONALDSON J. A. DONALDSON 1Department of Geology, Carleton University, Ottawa, Ontario, Canada K1S 5B6 Search for other works by this author on: GSW Google Scholar Author and Article Information P. S. MUSTARD 1Department of Geology, Carleton University, Ottawa, Ontario, Canada K1S 5B6 J. A. DONALDSON 1Department of Geology, Carleton University, Ottawa, Ontario, Canada K1S 5B6 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1987) 98 (4): 373–387. https://doi.org/10.1130/0016-7606(1987)98<373:EPIGDT>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 Email Tools Icon Tools Get Permissions Search Site Citation P. S. MUSTARD, J. A. DONALDSON; Early Proterozoic ice-proximal glaciomarine deposition: The lower Gowganda Formation at Cobalt, Ontario, Canada. GSA Bulletin 1987;; 98 (4): 373–387. doi: https://doi.org/10.1130/0016-7606(1987)98<373:EPIGDT>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 Mapping at 1:2,000 scale in the Cobalt area has allowed detailed interpretation of the glaciogenic deposystem for the basal 180 m of the Coleman Member, lowermost unit of the Gowganda Formation, Huronian Supergroup. Deposition at Cobalt occurred on the subsiding shelf of a south-facing passive margin. The unconformity that separates subhorizontal Coleman Member lithofacies from underlying Archean rocks exhibits a subdued topography and less than 100 m of relief. Evidence of plucking and lee-side quarrying of this surface support southerly movement of a grounded ice sheet. Massive basal diamictites were deposited subglacially as extensive primary basal till and as restricted lee-side till that infilled paleotopographic lows and covered preglacial regolith. Coarsening-upward rhythmite/sandstone/clast-supported diamictite associations were deposited as prograding subaqueous outwash fans in front of a slowly retreating wet-based tidewater ice sheet grounded in 50 to 300 m of water. Rhythmite characteristics indicate a distal change from underflow to interflow/overflow sediment-transport, supporting an ice-contact, marine-basin interpretation. Differences in dropstone abundance in the rhythmites suggest variable rates of ice-front calving and iceberg transport. Interfan areas received sediment from melt water and from abundant sediment gravity flows off over-steepened fan slopes and collapsing ice-marginal banks. An upper diamictite association contains dropstone diamictite, poorly laminated mudstones, diamictite with random clast orientations, and thick diamictite sequences characteristic of deposition from sediment gravity flows. These features suggest transition from a grounded to a partially floating ice sheet before deposition of the uppermost Coleman Member strata preserved at Cobalt. 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.