Search results
Results from the WOW.Com Content Network
Disconformity. A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. [3] Disconformities are marked by features of subaerial erosion. This type of erosion can leave channels and paleosols in the rock record. [4]
The example Hutton discovered is known as an angular unconformity in which a sharp change in younging direction can be seen in the orientation of bedding planes. The younging direction points from the oldest bed, to the youngest bed in the sequence of sedimentary beds.
It is an exceptional example of relatively young sedimentary rock strata overlying much older sedimentary or crystalline strata. The intervening period of geologic time is sufficiently long to raise the earlier rock into mountains which are then eroded away.
It also contains thin beds of shale and siltstone, and conglomerate. The Muav Limestone weathers to a dark gray or rusty-orange color and forms cliffs or small ledges. This formation varies between 45 and 254 m (148 and 833 ft) in thickness. Its upper contact is a disconformity with the overlying Frenchman Mountain Dolostone.
Siccar Point is notable in the history of geology as a result of a boat trip in 1788 in which geologist James Hutton observed the angular unconformity of the point. [2] He wrote later that the evidence of the rocks provided conclusive proof of the uniformitarian theory of geological development; that is, that the natural laws and processes which operate in the universe have never changed and ...
Within the Unkar Group, the contact between the Hakatai Shale and overlying Shinumo Sandstone is a distinct disconformity. This contact is the only significant unconformity that occurs within the Unkar Group. This disconformity is sharp and locally truncates cross-bedding and channels exhibited by sandstones in the underlying Hakatai Shale.
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 planes below and above the unconformity are parallel. A time gap is present, as shown by a faunal break, but ...
In geology and geomorphology, an erosion surface is a surface of rock or regolith that was formed by erosion [1] and not by construction (e.g. lava flows, sediment deposition [1]) nor fault displacement. Erosional surfaces within the stratigraphic record are known as unconformities, but not all unconformities are buried erosion surfaces.