geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

, a rock's fabric describes the spatial and geometric configuration of all the elements that make it up. In

sedimentary rock Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...

s, the fabric developed depends on the

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be ...

and can provide information on current directions at the time of deposition. In

structural geology Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover informatio ...

, fabrics may provide information on both the orientation and magnitude of the strains that have affected a particular piece of deformed rock.

Types of fabric

* Primary fabric — a fabric created during the original formation of the rock, e.g. a preferred orientation of

clast Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

long axes in a conglomerate, parallel to the flow direction, deposited by a fast waning current. * Shape fabric — a fabric that is defined by the preferred orientation of inequant elements within the rock, such as platy- or needle-like mineral grains. It may also be formed by the deformation of originally equant elements such as mineral grains. * Crystallographic preferred orientation — in plastically deformed rocks, the constituent minerals commonly display a preferred orientation of their crystal axes as a result of

dislocation In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to sl ...

processes. * S-fabric — a planar fabric such as cleavage or

foliation In mathematics (differential geometry), a foliation is an equivalence relation on an ''n''-manifold, the equivalence classes being connected, injectively immersed submanifolds, all of the same dimension ''p'', modeled on the decomposition of ...

; when it forms the dominant fabric in a rock, it may be called an S-

tectonite Tectonites are metamorphic or tectonically deformed rocks whose fabric reflects the history of their deformation, or rocks with fabric that clearly displays coordinated geometric features that indicate continuous solid (ductile) flow during fo ...

. * L-fabric — a linear fabric such as mineral stretching lineation where aggregates of recrystallised grains are stretched out into the long axis of the finite strain ellipsoid, where it forms the dominant fabric in a rock, it may be called an L-tectonite. * Penetrative fabric — a fabric that is present throughout the rock, generally down to the grain scale, although this does also depend on the scale at which the observations take place. *Magnetic fabric — orientation of magnetic particles within a rock sample or in soils to determine paleomagnetic history or to quantify tectonic strain.

Types of fabric

References

See also