Abstracts - GAC Newfoundland Section - 2008 Spring Technical Meeting

2008 Atlantic geology  
We are frequently asked why we refer to our annual technical meeting as the "Spring Meeting" when it is held in the depths of the Newfoundland winter, in late February. We have always had a strong sense of the absurd, and we are eternal optimists, but there is a more rational reason. In the past, the meeting was held as late as April, when the weather is truly more spring-like, even in St. John's. But we have for many years adopted a late February slot that coincides with mid-term break at
more » ... -term break at Memorial University. In 2008, we did actually have some spring-like wet and mild weather, which is certainly better than the mammoth snowstorm that buried us in 2007. This year's meeting was, by all accounts, a success, with over 125 registrants in total. In addition to the technical presentations at the meeting, the Newfoundland and Labrador Chamber of Mineral Resources sponsored a workshop on exploration for volcanogenic massive sulphide deposits. As has been the case for several years, the meeting was divided into a thematic session and a general session. The choice for the thematic session was driven by strong recent interest in VMS exploration, coupled with the fact that it is now 150 years since the very first discovery of this type in Newfoundland. The Terra Nova mine marked the start of Newfoundland's first mining boom and was in all probability one of the first VMS deposits mined in the territory of modern Canada. To mark these developments, our thematic session was entitled "VMS deposits in Newfoundland -150 years of discoveries". In the end, it included a variety of talks related to regional geology and VMS metallogeny, and extended beyond Newfoundland, to New Brunswick, northern Québec, offshore western Canada, and even to the South American country of Peru. We believe that variety is indeed the spice of professional meetings, and were happy to see such diverse contributions. The special session was in part supported by the Geological Survey of Canada's Targeted Geoscience Initiative (TGI) program, which is actively engaged in geological studies related to VMS environments in eastern Canada. A workshop related to TGI activities in Newfoundland also formed part of the agenda, and there were many presentations by GSC geologists involved in TGI. The general session this year was fairly short, but included talks on paleontology, Quaternary geology, regional geology and experiments on immiscible liquids applied to magmatic sulphides. GAC Newfoundland and Labrador is pleased to have once again hosted an interesting and diverse meeting, and we are equally pleased to see the abstracts published again in Atlantic Geology. Our thanks to all of the speakers and the editorial staff of the journal. This presentation describes the glacial history of Placentia Bay, Newfoundland as interpreted from both seabed and terrestrial glacial records. Multibeam sonar data, augmented by seismic and coring data revealed a range of flow-parallel and flow-transverse glacial landforms on the Placentia Bay seafloor. Flow-parallel landforms identified include drumlins, flutes, megaflutes and crag-and-tails. These landforms show a general trend of convergent flow, interpreted to represent fast-flowing ice which was converging into an ice stream down the axis of Placentia Bay. Flow-parallel landforms and striations from the surrounding land areas demonstrate that the convergent flow can be traced up-ice to regional ice dispersal centres. Flow-transverse landforms include De Geer moraines and grounding-line moraines. De Geer moraines occur in several fields throughout the bay marking the intermittent retreat of grounded ice up the bay. Radiocarbon dates from glaciomarine silt suggest that ice became ungrounded and glaciomarine sedimentation started by at least 16,080 yrs BP. Ice-flow mapping in Placentia Bay also demonstrated that the largely depositional record preserved on the seabed is incomplete, with the apparent absence of a strong westward flow onto the Burin Peninsula. The mostly erosional ice-flow record on land also appears incomplete because there is no evidence to date, for a northeast-southwest ice-flow that is recorded by a fluted field in southwestern Placentia Bay. Given the incomplete records on both the seabed and on land, the integration of seabed data with onshore glacial records provides a better understanding of the glacial history. This integrated approach also represents an important development in mapping palaeoice flows and the understanding of ice sheet behaviour during the transition from largely marine-based to land-based glacial conditions which may reflect the deglacial scenarios in other bays in Newfoundland and elsewhere.
doi:10.4138/5934 fatcat:7sanomxpqfgfde5th2vbby7ouy