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Petroleum Geological Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
Cross bedding refers to horizontally inclined sedimentary rock layers. Cross beds are groups of inclined layers. They are also known as ‘cross strata’. Cross bedding is formed during deposition on an inclined surface, in the presence of suitable sediments and flowing water or blowing wind.
Minerals, rocks and sediments
Published in Richard J. Chorley, Stanley A. Schumm, David E. Sugden, Geomorphology, 2019
Richard J. Chorley, Stanley A. Schumm, David E. Sugden
For general purposes, the two major types are graded bedding and cross-bedding. Graded bedding (Figure 4.12A) is a very common form of stratification in which grain size increases towards the base of each bed. Such vertical grading may be produced in a number of ways, such as by differences in the settling velocities of sedimentary particles in a given sedimentary ‘flush’, by rapid pulsating sedimentation under stable conditions, settling from turbidity currents within water or air (e.g. nuees ardente), or a general decrease in grain size in the provenance during slower sedimentation over a longer period of time. Such a consideration of sedimentation mechanisms shows the wide range of sedimentation rates which are possible, varying from the virtually instantaneous deposition by floods, mudflows, or sand dune invasion to much slower rates under offshore marine conditions. Some thin beds and laminations can be directly related to individual seasonal (e.g. varves) or tidal variations in sedimentation.
Genesis of hummocks found in tunnel valleys: an example from Hörda, southern Sweden
Published in GFF, 2018
Gustaf Peterson, Mark D. Johnson, Sandra Dahlgren, Tore Påsse, Helena Alexanderson
The lower and southern parts of the section consist of sorted sediment with a grain size from silt to granules. This unit is generally coarser in the lower part and sandier in the upper. The sorted sediments are often massive, but in places there is lamination and bedding. Cross-bedding (trough cross-bedding in places) and sub-horizontal bedding or lamination are most common. In the middle part, there is a unit difficult to separate into distinct silt, sand or gravel beds. This part of the silt to granule unit is referred to as an amalgamated sub-unit, Amu (Table 1, Figs. 4 and 5C).
Paleocurrent and paleowind direction reconstruction research progress and perspectives: a review
Published in Australian Journal of Earth Sciences, 2023
F. Y. Zhao, C. L. Hu, C. C. Han, Y. Q. Dong, Q. X. Yuan
Cross-bedding caused by water flow can directly reflect the hydrodynamic conditions at the time of sedimentation. The dip direction of the foreset of the cross-bedding is the paleocurrent direction (Du, 2018). Cross-bedding includes structures formed by unidirectional flow and bidirectional flow. Generally, the paleocurrent direction can be truly determined only from the cross-bedding formed by the unidirectional flow.