bysmalith

Bysmaliths are more or less vertical and cylindrical bodies that crosscut (discordant) adjacent sediments and are bounded by steep faults. Bymaliths are commonly associated with the mountain-building (orogenic) processes, and they are typically composed of granites or granodiorites.

Bysmaliths are considered to be conical or cylindrical laccoliths. They develop when highly viscous magma is injected into strata. Because lateral spreading along the bedding is limited by viscosity, the magma moves upward to form the cylindrical shape. Overlying rock layers are fractured. The walls of bysmaliths slope away from each other with depth, which makes their diameter increasingly large at greater depths.

[image Black Mesa bysmalith (Henry Mountains, Colorado Plateau, Utah), close-up of Wolf porphyry, Mixes Baldy-Anderson Peak Bysmalith close to the Blankenship Divide; ref, ref 2, gallery, Henry Mountains Wilderness]

concordant

Concordant or conformable, when referring to plutonic bodies, indicates that the intruding magma of sills and laccoliths lies parallel to rather than cutting across country strata, as do discordant structures such as veins, dikes, bysmoliths, and batholiths.

A concordant coastline comprises bands of different rock types that run parallel to the shore. The rock types are typically of alternating resistance, so that the coastline forms distinctive landforms, such as coves. A discordant coastline comprises rock types of alternating resistance that run perpendicular to the shore, creating distinctive landforms when the rocks are eroded by ocean waves. Less resistant rocks erode faster, creating inlets or bays; more resistant rocks erode more slowly, remaining as headlands or outcroppings.

Concordant flows at different points in a river system have the same recurrence interval, or the same frequency of occurrence. The term is most often applied to floodflows.

phacoliths

Phacoliths are concordant plutonic bodies that lie parallel to the bedding plane or foliation of folded country rock. They occur along the crests of anticlines or the troughs of synclines in folded sedimentary strata.

Rarely, the body of a phacolith may extend as a sill from the crest of an anticline through the trough of an adjacent syncline, such that it has an S shape in cross section. The hinge of folds in intensely folded terrains are areas of reduced pressure, so are potential sites for magma migration and emplacement.

[links: images: close-up: autolith of biotite-rich, enclave bearing, porphyritic granite in another more phenocrystic granite, Wolf Mountain Intrusion (Phacolith), Proterozoic Llano Uplift, central Texas]