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Geology is the Way

Plane bedding

Plane bedding (or parallel bedding) is the simplest sedimentary structure. It occurs when bedding planes are parallel to each other. In undisturbed (non deformed) sedimentary sequences, plane bedding continues laterally as horizontal beds at the scale of kilometers to hundreds of kilometers. Beds end against the margins of the sedimentary basin or gradually fades into progressively thinner beds, moving away from the source area of the sediment. Plane bedding is common in marine environments (especially deep marine environments), where it may form as the result of slow deposition of suspended, pelagic sediments or the rapid deposition of layers due to a fast hydrodynamic event (i.e. turbidity currents). In shallow waters, plane bedding may mark alternating periods of slow deposition and storms that deposit coarser sediments. In pelagic carbonates and cherts, formed by the settling of microorganisms on the seafloor, bedding may mark cyclical changes in the productivity of these organisms, for example related to fluctuations in the Earth’s orbit (astronomical changes).

Plane lamination or parallel lamination is defined by small scale parallel bands (< 1 cm) of different lithology or grain size. In lacustrine deposits close to glacier, small, seasonal changes in sediment supply (summer/winter cyclical changes in melting of glaciers) produce a special type of parallel laminae called glacial varves. In most cases, however, parallel laminae are the result of strong, tractive currents (upper flow regime) that drag sediment at the bottom of a basin, forming finely alternating laminae.

plane beds

Plane, horizontal beds, defined by variations in color that flag lithologic alternations, at the Quebrada de Cafayate, Salta, Argentina. Photo by travelwayoflife.

bedding in the Kaibab Limestone

The Kaibab Limestone is a geologic formation of the Colorado Plateau. Plane bedding is defined by finely interbedded layers of limestone/dolomite (prominent layers) and shale/sandstone (eroded layers). In this case, plane bedding is interpreted to have originated from fluctuations of the sea level, which determined a change from a shallow marine environment (carbonate sedimentation) to coastal/tidal environments (siliciclastic sedimentation). Walnut Canyon, Arizona, USA. Photo Samuele Papeschi/GW. [BLOG POST]

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Ripples in sand

  • Bedforms: ripples and dunes Ripples, dunes, antidunes are all bedforms, structures that form in sand when it is moved by water or wind. Bedforms are ubiquitous on our planet. It is very common to see ripples, undulatory structures in sand, under shallow waters close to seashores or along riverbanks. And deserts, they are commonly covered with large sand dunes, in turn sprinkled by smaller… Read More »Bedforms: ripples and dunes

References
Campbell, C. V. (1967). Lamina, laminaset, bed and bedset. Sedimentology8(1), 7-26.
Ingram, R. L. (1954). Terminology for the thickness of stratification and parting units in sedimentary rocks. Geological Society of America Bulletin65(9), 937-938.
Lyell, C., & Deshayes, G. P. (1830). Principles of geology: being an attempt to explain the former changes of the earth’s surface, by reference to causes now in operation (Vol. 1). J. Murray.
Mackenzie, F. T., & Garrels, R. M. (1971). Evolution of sedimentary rocks. New York: Norton.
McKee, E. D., & Weir, G. W. (1953). Terminology for stratification and cross-stratification in sedimentary rocks. Geological Society of America Bulletin64(4), 381-390.
Pettijohn, F. J. (1975). Sedimentary rocks (Vol. 3). New York: Harper & Row.
Schlager, W. (2004). Fractal nature of stratigraphic sequences. Geology32(3), 185-188.
Steno, N. (1669). De Solido Intra Solidium Naturaliter Contento Dissertationis Prodromus: Florence, Italy, Library of Grand Duke Ferdinand II, – V. iv, 131 p. English version: Stensen, Niels 1671, The prodromus to a dissertation concerning solids naturally contained within solids. J. Winter, London, 112 p.

        

See also
Features from the Field – bedding/stratification – EGU Tectonics & Structural Geology Blog.
SEPM Strata – Bed.
SEPM Strata – Bedding plane

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Detrital and Authigenic Minerals
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Sedimentary Structures
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Sedimentary Rocks

 

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