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The AAPG/Datapages Combined Publications Database
Journal of Sedimentary Research (SEPM)
Abstract
Ripple Marks in Quartz Arenites of the Hurwitz Group, Northwest Territories, Canada: Evidence for Sedimentation in a Vast, Early Proterozoic, Shallow, Fresh-Water Lake
Lawrence B. Aspler (1), Jeffrey R. Chiarenzelli (2), Terry L. Bursey (3)
ABSTRACT
Supermature quartz arenites of the Whiterock Member, deposited in the Early Proterozoic, intracratonic Hurwitz Basin, have a maximum thickness of 400 m and a minimum areal extent of 100,000 km2. The unit is unusual in that it is virtually devoid of other rock types and displays sedimentary structures that consist almost entirely of short-spaced ripple marks and parallel stratification, both formed by oscillatory flow. The ripples have spacings that are consistently small (average < 5 cm) for the entire thickness and lateral extent of the unit. Application of empirical and analytical methods yields average water depths in the range 2 cm to 2 m (maximum 5.6 m). Apparently, shallow water was maintained over a Large area for a long period of time, yet evidence of tidal and e aporitic conditions are lacking. We interpret that sedimentation was in a large, hydrographically open, tide-free, fresh-water lake, or series of lakes, that occupied a low-relief continental depression in a wet, possibly equatorial, climate where continuously high rainfall and well-developed outlets combined to prevent raised salinities.
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