Stratigraphic relationship
Two types of contact: Conformable and Unconformable.
Conformable: Unbroken deposition, no break or hiatus (break or interruption in the continuity of the geological record). The surface strata resulting is called a conformity.
Two types of contact between conformable stata: Abrupt contacts ( Directly separate beds of distinctly different lithology, minor depositional break, called Diastems) Gradational contact (Gradual change in deposition, mixing zone).
Unconformable: Period of erosion/non-deposition. The surface stratum resulting is called an unconformity.
Unconformity. A surface of erosion between rock bodies that represents a significant hiatus or gap in the stratigraphic succession. Therefore, unconformity-bounded units are bodies of rocks bounded above and below by significant unconformities. They are composed of diverse types of any kind or kinds of rocks, but the lithologic properties of these rocks, their fossil content, or the chronostratigraphic span of the rocks on either side of the bounding unconformities are significant only to the extent that they serve to recognize the bounding unconformities
Four types of unconformity
Angular unconformity . An unconformity in which the bedding planes above and below the unconformity are at an angle to each other.
Disconformity The contact between younger and older beds is marked by visible, irregular erosional surfaces. Paleosol might develop right above the disconformity surface because of the non-deposition setting.
Paraconformity The bedding plans below and above the unconformity are parallel. A time gap is present but there is no erosion, just a non-deposition period.
Nonconformity Relatively young sediments are deposited right above older Igneous or metamorphic rocks.
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