2006 Philadelphia Annual Meeting (22–25 October 2006)

Paper No. 4
Presentation Time: 2:20 PM


RAUB, Timothy D.1, EVANS, David A.D.1 and SPERLING, Erik A.2, (1)Department of Geology and Geophyics, Yale Univ, P.O. Box 208109, New Haven, CT 06520-8109, (2)Department of Geology and Geophysics, Yale University, P.O. Box 208109, New Haven, CT 06520-8109, timothy.raub@yale.edu

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.