EARTH238-2b- Primary Structures Part 2

Types of contacts

depositional contact, fault contact, intrusive contact

Comfortable Contact

Depositional; more or less continuous deposition, no substantial gap in time

Uncomforable contact (uncomformity)

Not continuous deposition, substantial gap in time

Hiatus

gap in time represented by an uncomformity

Angular uncomformity

strata below unconformity have a different attitude than the strata above

Disconformity

beds of the rock sequence below uncomformity are parallel, but measurable age difference between the two

Noncomformity

strata deposited on the basement of older crystalline rocks

Pressure solution

process which soluble grains preferentially dissolve along the faces at which stress is the greatest

styolites

serrate surfaces at which minerals have been removed by pressure dissolution in a process by decreasing a total volume of rock

Primary igneous structures

magma emplaced either on surface(extrusive) or within the crust(intrusive rocks), felsic and mafic

Cooling fractures

columnar jointing, associated with shallow intrusions and extrusive flows, hexagonal.