The Oldman Formation is a stratigraphic unit of Late Cretaceous ( Campanian stage) age that underlies much of southern Alberta , Canada . It consists primarily of sandstones that were deposited in fluvial channel and floodplain environments. It was named for exposures along the Oldman River between its confluence with the St. Mary River and the city of Lethbridge , and it is known primarily for its dinosaur remains and other fossils.
12-548: The Oldman Formation is composed primarily of light-colored, fine-grained sandstones. They are upward-fining, lenticular to sheet-like bodies that are yellowish, steep-faced and blocky in outcrop . The formation also includes lesser amounts of siltstone and mudstone . The sediments of the Oldman Formation were deposited in fluvial channels (the sandstones) and a variety of channel margin, overbank and floodplain environments (the siltstones and mudstones). The formation
24-759: A continuous line along the top edge with lines protruding down; outcrops have a continuous line around each area of bare rock. An outcrop example in California is the Vasquez Rocks , familiar from location shooting use in many films , composed of uplifted sandstone . Yana is another example of outcrops, located in Uttara Kannada district in Karnataka , India . Principle of original horizontality The principle of original horizontality states that layers of sediment are originally deposited horizontally under
36-539: A record of relative changes within geologic strata . Accurate description, mapping, and sampling for laboratory analysis of outcrops made possible all of the geologic sciences and the development of fundamental geologic laws such as the law of superposition , the principle of original horizontality , principle of lateral continuity , and the principle of faunal succession . On Ordnance Survey maps in Great Britain , cliffs are distinguished from outcrops: cliffs have
48-594: A regional disconformity. The sediments of the Oldman are superficially similar to those of the Dinosaur Park, which was included in the Oldman Formation prior to the recognition of the disconformity. The two formations can also be distinguished by petrographic and sedimentologic differences. The Oldman Formation was deposited during the middle Campanian , between about 77.5 and 76.5 million years ago. It lies fully within magnetic polarity Chron 33n . List of dinosaurs found in
60-612: Is about 40 metres (130 ft) thick at Dinosaur Provincial Park in southeastern Alberta. It thickens toward the southwest, and northwestern Montana appears to have been the primary source of the sediments. The Oldman Formation is a member of the Belly River Group (also known as the Judith River Group ). It conformably overlies the Foremost Formation , and is separated from the overlying Dinosaur Park Formation by
72-471: The Earth's surface due to human excavations such as quarrying and building of transport routes. Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geologic maps . In situ measurements are critical for proper analysis of geological history and outcrops are therefore extremely important for understanding the geologic time scale of earth history. Some of
84-464: The action of gravity . It is a relative dating technique. The principle is important to the analysis of folded and tilted strata . It was first proposed by the Danish geological pioneer Nicholas Steno (1638–1686). From these observations is derived the conclusion that the Earth has not been static and that great forces have been at work over long periods of time, further leading to the conclusions of
96-424: The formation: Outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets . Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficial deposits are covered by soil and vegetation and cannot be seen or examined closely. However, in places where
108-484: The internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort. This is known as the angle of repose , and a prime example is the surface of sand dunes . Similarly, sediments may drape over a pre-existing inclined surface: these sediments are usually deposited conformably to the pre-existing surface. Also, sedimentary beds may pinch out along strike , implying that slight angles existed during their deposition. Thus
120-580: The overlying cover is removed through erosion or tectonic uplift , the rock may be exposed, or crop out . Such exposure will happen most frequently in areas where erosion is rapid and exceeds the weathering rate such as on steep hillsides, mountain ridges and tops, river banks, and tectonically active areas. In Finland , glacial erosion during the last glacial maximum (ca. 11000 BC), followed by scouring by sea waves, followed by isostatic uplift has produced many smooth coastal and littoral outcrops. Bedrock and superficial deposits may also be exposed at
132-469: The science of plate tectonics ; that movement and collisions of large plates of the Earth's crust is the cause of folded strata . As one of Steno's Laws, the principle of original horizontality served well in the nascent days of geological science . However, it is now known that not all sedimentary layers are deposited purely horizontally. For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by
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#1732844356794144-468: The types of information that cannot be obtained except from bedrock outcrops or by precise drilling and coring operations, are structural geology features orientations (e.g. bedding planes, fold axes, foliation ), depositional features orientations (e.g. paleo-current directions, grading, facies changes), paleomagnetic orientations. Outcrops are also very important for understanding fossil assemblages, and paleo-environment, and evolution as they provide
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