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Straight ripples generate cross-laminae that all dip in the same direction, and lie in the same plane. These forms of ripples are constructed by unidirectional flow of the current. Sinuous Sinuous ripples generate cross-laminae that are curvy. They show a pattern of curving up and down as shown in picture.
Bidirectional wave ripple, Nomgon, Mongolia. A paleocurrent or paleocurrent indicator is a geological feature (typically a sedimentary structure) that helps one determine the direction of flowing water in the geologic past. This is an invaluable tool in the reconstruction of ancient depositional environments. [1]
In sedimentology, wave-formed ripples or wave-formed ripple marks are a feature of sediments (sandstones, limestones, siltstones) and dunes. These ripple marks are often characterised (and thus distinguished from current ripples ) by symmetric cross sections and long relatively straight crests, which may commonly bifurcate.
Giant current ripples usually exhibit antidune breaking wave and dune ripple shapes, resulting from their high energy environments. Giant current ripples can reach a maximum height of 20 metres (66 ft) and reach a maximum length of 1 kilometre (0.62 mi). they occur in ripple fields that can cover an area several kilometers across. [3] [6]
Modern asymmetric ripples developed in sand on the floor of the Hunter River, New South Wales, Australia. Flow direction is from right to left. Sinuous-crested dunes exposed at low tide in the Cornwallis River near Wolfville, Nova Scotia Ancient channel deposit in the Stellarton Formation (Pennsylvanian), Coalburn Pit, near Thorburn, Nova Scotia.
Current ripples preserved in sandstone of the Moenkopi Formation, Capitol Reef National Park, Utah, United States. A bedform is a geological feature that develops at the interface of fluid and a moveable bed, the result of bed material being moved by fluid flow. Examples include ripples and dunes on the bed of a river.
Patterns in Nature. Little, Brown & Co. Stewart, Ian (2001). What Shape is a Snowflake? Magical Numbers in Nature. Weidenfeld & Nicolson. Patterns from nature (as art) Edmaier, Bernard. Patterns of the Earth. Phaidon Press, 2007. Macnab, Maggie. Design by Nature: Using Universal Forms and Principles in Design. New Riders, 2012. Nakamura, Shigeki.
Asymmetrical ripple marks These are created by a one way current, for example in a river, or the wind in a desert. This creates ripple marks with still pointed crests and rounded troughs, but which are inclined more strongly in the direction of the current. For this reason, they can be used as palaeocurrent indicators.