Lenticular bedding

Lenticular bedding refers to a sedimentary layering pattern where isolated lenses or pockets of sand are preserved within thick layers of mud due to a high proportion of mud compared to sand. This type of bedding can be observed in small-scale cross-bedded sets where mud drapes converge towards the base, and is commonly found in environments with significant lateral variation in depositional processes and/or erosion.From: Introduction to Sedimentology [2017], Quaternary sedimentology and tephrostratigraphy of the lower Pohangina Valley, New Zealand [2019], Sedimentary Rocks in the Field [2019]

Hydraulics, Sediment Transportation and Structures of Mechanical Origin

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Published in Supriya Sengupta, Introduction to Sedimentology, 2017

Supriya Sengupta

When the depositional system contains mud as well as sand, intermittent breaks in the current flow may lead to preservation of streaks of mud within the ripple troughs. The resultant structures have been termed flaser bedding (Reineck and Wunderlich 1968). With increasing proportions of mud, wavy beddings are produced. When the proportion of mud is very high compared to that of sand, only isolated lenticles of sand may be preserved within thick layers of mud, leading to what has been termed lenticular bedding (Fig. 5.17).

Quaternary sedimentology and tephrostratigraphy of the lower Pohangina Valley, New Zealand

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Published in New Zealand Journal of Geology and Geophysics, 2019

Callum Rees, Alan Palmer, Julie Palmer

The volcaniclastic facies of the Takapari Formation (Facies He, Sh and Sp) are composed of nearly pure vitric pumiceous sandstone ranging in thickness from 4 to 17 m. Grain sizes range from granular to fine sand. Some units contain sub-rounded pumice clasts up to 150 mm in size (Figure 4). Primary sedimentary structures indicative of subaqueous deposition in a tidal environment include bidirectional cross bedding, mud drapes and ripple to lenticular bedding. Cross stratification ranges from millimetre scale ripples to 2 m scale trough crossbedding. In some cases (bed 9–16, Figure 2), the entire range of cross stratification occurs in a single volcaniclastic unit, suggesting a rapid change in paleo-current strength. Generally sedimentary structures indicate very variable flow strength up section, with many changes from low flow (ripples) to higher flow (cross beds, laminae) indicators.

Lenticular bedding

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Hydraulics, Sediment Transportation and Structures of Mechanical Origin

Quaternary sedimentology and tephrostratigraphy of the lower Pohangina Valley, New Zealand