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A bedding surface is three-dimensional surface, planar or curved, that visibly separates each successive bed (of the same or different lithology) from the preceding or following bed. Where bedding surfaces occur as cross-sections, e.g., in a 2-dimensional vertical cliff face of horizontal strata, are often referred to as bedding contacts .
These structures are within sedimentary bedding and can help with the interpretation of depositional environment and paleocurrent directions. They are formed when the sediment is deposited. Cross-bedding Cross-bedding is the layering of beds deposited by wind or water inclined at an angle as much as 35° from the horizontal. [1]
Graded bedding is a sorting of particles according to clast size and shape on a lithified horizontal plane. The term is an explanation as to how a geologic profile was formed. Stratification on a lateral plane is the physical result of active depositing of different size materials.
Tabular cross-bedding, or planar bedding consists of cross-bedded units that are extensive horizontally relative to the set thickness and that have essentially planar bounding surfaces. [3] Trough cross-bedding, on the other hand, consists of cross-bedded units in which the bounding surfaces are curved, and hence limited in horizontal extent. [3]
The foliations are symmetrically arranged with respect to the axial plane, depending on the composition and competency of a rock. For example, when mixed sandstone and mudstone sequences are folded during very-low to low grade metamorphism, cleavage forms parallel to the fold axial plane, particularly in the clay-rich parts of the sequence.
These planes or weakened areas allow the intrusion of a thin sheet-like body of magma paralleling the existing bedding planes, concordant fracture zone, or foliations. Sills run parallel to beds (layers) and foliations in the surrounding country rock. They can be originally emplaced in a horizontal orientation, although tectonic processes may ...
Structural geologists measure a variety of planar features (bedding planes, foliation planes, fold axial planes, fault planes, and joints), and linear features (stretching lineations, in which minerals are ductilely extended; fold axes; and intersection lineations, the trace of a planar feature on another planar surface).
The bedding surfaces (bedding planes) that separate strata represent episodic breaks in deposition associated either with periodic erosion, cessation of deposition, or some combination of the two. [ 3 ] [ 4 ] Stacked together with other strata, individual stratum can form composite stratigraphic units that can extend over hundreds of thousands ...