| Trout Valley Formation Stratigraphic range: Devonian | |
|---|---|
| Type | Formation |
| Location | |
| Region |  Maine |
| Country |  United States |
The Trout Valley Formation is a geologic formation in Maine. It preserves fossils dating back to the Devonian period.
| Trout Valley Formation Stratigraphic range: Devonian | |
|---|---|
| Type | Formation |
| Location | |
| Region | Maine |
| Country | United States |
The Trout Valley Formation is a geologic formation in Maine. It preserves fossils dating back to the Devonian period.
Situated in north-central Maine, the Trout Valley Formation is located in a fault-bounded basin. An erosional unconformity separates it from underlying felsites. The formation exists entirely within the confines of Baxter State Park, and collecting of materials without authorization is prohibited.
The formation represents an alluvial fan draining an active volcanic source [1] and has a basal cobble conglomerate, consisting only of rounded fragments of the underlying volcanic felsite, known formally as the Traveler Rhyolite. The conglomerate is overlain by sandstone, which contains lenses of gray shale, black shale and fine conglomerate, in a generally fining-upward sequence. The unit's distal portions terminate in tidal mudflats, which have produced a bivalve-dominated fauna that also yielded the first relatively complete Eurypterid found in northern New England. [2]
The Trout Valley Formation also contains fossilized Psilophyton plants, as well as a number of other taxa, including Pertica quadrifaria, the official state fossil, [3] the tallest plant of its age known from anywhere in the world. The Trout Valley Formation earlier was dated to the Early Devonian by the presence of fossilized eurypterid scales, possible estherids and ostracods, but is now assigned to the early Middle Devonian (Emsian); it is believed to be 3-5 million years older than the Gilboa Fossil Forest of New York.
In contrast to the Traveler Rhyolite and sandstones beneath the Trout Valley Formation, which have open folds, the formation itself is unfolded. However, normal bed-parallel faulting within the sandstones suggest that uplift may have been taking place during deposition. This suggests that the Trout Valley Formation was deposited after the tectonic activity that altered the underlying rocks, but before that which uplifted the mountains in this area had come to completion. Although the Katahdin Pluton cuts through the Traveler Rhyolite, granitic fragments from the Katahdin Pluton have never been found in the Trout Valley Formation. At least one minor dike of Traveler Rhyolite has, however, been found cutting through the rocks of the Trout Valley Formation.
The Llano Uplift is a geologically ancient, low geologic dome that is about 90 miles (140 km) in diameter and located mostly in Llano, Mason, San Saba, Gillespie, and Blanco counties, Texas. It consists of an island-like exposure of Precambrian igneous and metamorphic rocks surrounded by outcrops of Paleozoic and Cretaceous sedimentary strata. At their widest, the exposed Precambrian rocks extend about 65 miles (105 km) westward from the valley of the Colorado River and beneath a broad, gentle topographic basin drained by the Llano River. The subdued topographic basin is underlain by Precambrian rocks and bordered by a discontinuous rim of flat-topped hills. These hills are the dissected edge of the Edwards Plateau, which consist of overlying Cretaceous sedimentary strata. Within this basin and along its margin are down-faulted blocks and erosional remnants of Paleozoic strata which form prominent hills.
The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and shales. Based on argon radiometric dating, the formation is Eocene in age and has been interpreted as a lake environment. The fossils have been preserved because of the interaction of the volcanic ash from the nearby Thirtynine Mile volcanic field with diatoms in the lake, causing a diatom bloom. As the diatoms fell to the bottom of the lake, any plants or animals that had recently died were preserved by the diatom falls. Fine layers of clays and muds interspersed with layers of ash form "paper shales" holding beautifully-preserved fossils. The Florissant Fossil Beds National Monument is a national monument established to preserve and study the geology and history of the area.
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The Huntersville Chert or Huntersville Formation is a Devonian geologic formation in the Appalachian region of the United States. It is primarily composed of mottled white, yellow, and dark grey chert, and is separated from the underlying Oriskany Sandstone by an unconformity. The Huntersville Chert is laterally equivalent to the Needmore Shale, which lies north of the New River. It is also laterally equivalent to a sandy limestone unit which is often equated with the Onondaga Limestone. These formations are placed in the Onesquethaw Stage of Appalachian chronostratigraphy, roughly equivalent to the Emsian and Eifelian stages of the broader Devonian system.
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The geology of Cambodia is the study of the nation's rocks, minerals, water and landforms. Cambodia's ancient geologic history in the Precambrian is poorly understood. The region experienced tectonic activity and low-grade metamorphic rock formation throughout the Paleozoic, which a shift to marine conditions and fossil formation during the Permian and through much of the Mesozoic. Few rocks remain from the Cenozoic. Cambodia has comparatively few natural resources, although there is bauxite formed from laterite weathering, as well as phosphorite, iron, gems, limestone and other materials.
The geology of Georgia is the study of rocks, minerals, water, landforms and geologic history in Georgia. The country is dominated by the Caucasus Mountains at the junction of the Eurasian Plate and the Afro-Arabian Plate, and rock units from the Mesozoic and Cenozoic are particularly prevalent. For much of its geologic history, until the uplift of the Caucasus, Georgia was submerged by marine transgression events. Geologic research for 150 years by Georgian and Russian geologists has shed significant light on the region and since the 1970s has been augmented with the understanding of plate tectonics.
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The geology of Laos includes poorly defined oldest rocks. Marine conditions persisted for much of the Paleozoic and parts of the Mesozoic, followed by periods of uplift and erosion. The country has extensive salt, gypsum and potash, but very little hydrocarbons and limited base metals.
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The geology of Uzbekistan consists of two microcontinents and the remnants of oceanic crust, which fused together into a tectonically complex but resource rich land mass during the Paleozoic, before becoming draped in thick, primarily marine sedimentary units.
The geology of Thailand includes deep crystalline metamorphic basement rocks, overlain by extensive sandstone, limestone, turbidites and some volcanic rocks. The region experienced complicated tectonics during the Paleozoic, long-running shallow water conditions and then renewed uplift and erosion in the past several million years ago.
The geology of Yukon includes sections of ancient Precambrian Proterozoic rock from the western edge of the proto-North American continent Laurentia, with several different island arc terranes added through the Paleozoic, Mesozoic and Cenozoic, driving volcanism, pluton formation and sedimentation.
The geology of California is highly complex, with numerous mountain ranges, substantial faulting and tectonic activity, rich natural resources and a history of both ancient and comparatively recent intense geological activity. The area formed as a series of small island arcs, deep-ocean sediments and mafic oceanic crust accreted to the western edge of North America, producing a series of deep basins and high mountain ranges.
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