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Journal of Sedimentary Petrology, Vol. 43, No. 2 (1973), 418-422 OSTLER LENSES: POSSIBLE ENVIRONMENTAL INDICATORS IN FLUVIAL GRAVELS AND CONGLOMERATES I. PETER MARTINI and JOHN OSTLER Department of Land Resource Science, University of Guelph, Guelph, Ontario N1G 2W1 The Ostler lens is a sedimentary structure observed in recent and ancient coarse gravelly sequences. In recent environments they are small dun es, mounds or small transverse bars
made up of rounded, sorted small pebbles. They have been observed in streams
carrying predominantly coarse gravel to fine pebble materials, usually in
shallow reaches at the downstream end of braid islands, bars and point bars. The Ostler lenses are considered to record essentially unidirectional to slightly
convergent flow and a turbulent lower flow regime conditions for the riffle
(shallower) parts of alluvial channels.
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