T164 Magnetostratigraphy of Critical Intervals in Earth History: Contributions to Geochronology, Geobiology, Paleogeography, and Global Change

Tuesday, 24 October 2006
1:30 PM - 5:30 PM

DEGLACIAL STRATIGRAPHY AND PALEOMAGNETISM OF THE GASKIERS-DROOK TRANSITION, AVALON PENINSULA, NEWFOUNDLAND

Paper number: T164-4
Program: Technical Sessions
Time: 2:20 PM – 2:35 PM

Authors

Abstract

Newfoundland's Avalon Zone contains six outcrop belts where purportedly glacial-influenced massive diamictite of mid-Ediacaran Gaskiers Formation, reddened near its top, interrupts a kilometers-thick succession of otherwise monotonous and dark-colored, relatively coarse-grained siliciclastics. At Harbour Main, a decimeter-scale carbonate hosting red shale interbeds and green chert concretions caps the glacial succession. While this carbonate hosts a negative inorganic carbon isotope anomaly, lateral continuity of outcrop is limited, and it is unclear whether Gaskiers Formation manifests a final Precambrian "Snowball" glaciation, or Phanerozoic-style glaciation of moderate severity.

We report four fine-scale lithostratigraphies supporting paleomagnetic sampling of Gaskiers-Drook transition in southern Avalon, and we suggest lateral continuity of cap carbonate deposition, ranging from centimeter to decimeter scale, in three more Gaskiers outcrop belts. Anomalously fine-grained postglacial siliciclastic deposition is reddest immediately beneath the cap carbonate interval, and bed color darkens upsection. An organic-rich unit, expressed rarely as framboid-bearing black shale, culminates this fine-grained interval before massive Drook turbidites return to the succession. The 20-30 m of siltstone and shale presumably recording the deglacial aftermath of Gaskiers glaciation appears as anomalous, in the Avalonian succession, as the diamictite sequence itself.