HR: 08:15h
AN: T51D-02    [Abstracts]
TI: Pre-, Syn- And Post-Rodinian Detrital Zircon Record From Sedimentary Successions, Northeast Laurentia
AU: * Cawood, P A
EM: pcawood@tsrc.uwa.edu.au
AF: University of Western Australia, TSRC, 35 Stirling Highway, Crawley, WA 6009 Australia
AU: Nemchin, A A
EM: a.nemchin@curtin.edu.au
AF: Curtin University of Technology, WASM, Locked Bag 22, Kalgoorlie, WA 6433 Australia
AU: Strachan, R
EM: rob.strachan@port.ac.uk
AF: University of Porstmouth, School of Earth & Environmental Sciences, Portsmouth, PO1 3QL United Kingdom
AU: Prave, T
EM: ap13@st-and.ac.uk
AF: University of St Andrews, School of Geography and Geosciences, St Andrews, KY16 9AL United Kingdom
AB: Dating of detrital mineral suites is a powerful tool to assist palaeogeographic and tectonic reconstructions. Late Mesoproterozoic to early Paleozoic siliciclastic rocks are widespread around the margins of Laurentia. In northeast Laurentia these can be divided into three lithotectonic groupings on the basis of their age relations with respect to the supercontinent Rodinia. Group 1 units consist of late Mesoproterozoic successions that pre-date assembly of Rodinia and include the little deformed sequences of the Stoer Group of northeast Scotland, the Composite Arc Belt of the Grenville Orogen, and the Mid-Continent Rift System. Detrital zircons from the Stoer Group are dominated by Archaean detritus with minor Palaeoproterozoic detritus and no Mesoproterozoic detritus, whereas those from the Composite Arc Belt and related units show a range of ages from latest Archean to end Mesoproterozoic. Group 2 units are of early Neoproterozoic age and occupied an intracratonic position within an assembled Rodinia, which in northeast Laurentia was bordered by Baltica to the east and probably Amazonia to the southeast. Group 2 included the early latest Mesoproterozoic to early Neoproterozoic Moine and equivalent successions of Scotland, the Torridon Group, also of Scotland, and the Krummedal and lower Eleonore Bay supergroups of Greenland. These are characterized by late Paleoproterozoic and Mesoproterozoic zircon detritus with Archean age zircons absent or rare, except for the Torridon Group where they form a significant component. Group 3 consist of late Neoproterozoic to early Paleozoic successions that accumulated during the breakup of the Rodinia supercontinent and include Neoproterozoic to Cambrian siliciclastic sequences in Newfoundland, the Dalradian sequence in Scotland, and the upper Eleonore Bay Supergroup, Tillite Group and Zebra Series in East Greenland. The detrital zircon record of the group is characterized by late Archean, late Paleoproterozoic, and Mesoproterozoic detritus, except for the lower Dalradian succession (Grampian Group) which lacks Archean detritus. The significant features of this detrital zircon record with respect to the temporal and spatial paleogeographic evolution of northeast Laurentia are the variable distribution of Mesoproterozoic detritus in Group 1 and 2 units as well as the general paucity of Archean detritus is Group 2 sequences. The absence of Mesoproterozoic detritus in the Stoer Group is consistent with its inferred depositional age of around 1.2 Ga, predating Grenville orogenesis whereas metasedimentary sequences in the Composite Arc Belt are interstratified with metavolcanic sequences and contain Mesoproterozoic detritus related to accretionary assembly of the Grenville orogen, but predate final collisional orogenesis. The strong input of Mesoproterozoic detritus in Group 2 and 3 units indicates development of the Grenville orogenic welt during assembly of Rodinian and its subsequent maintenance as a source region during development of the passive margin succession along the East Laurentia margin that faced an open Iapetus Ocean. The general absence of Archean detritus in Group 2 units could reflect the Grenville Orogen acting as a barrier to input from the cratonic interior of Laurentia or the blanketing of Archean source regions by late Mesoproterozoic strata (e.g. Stoer and Torridon groups).
DE: 8099 General or miscellaneous
DE: 8102 Continental contractional orogenic belts
DE: 1815 Erosion and sedimentation
DE: 1035 Geochronology
DE: 1625 Geomorphology and weathering (1824, 1886)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting