The field data gathered then form the basis for a paper titled: "Geologic History of the Sheep Mountain Region". The shortening and thickening of the crust elevated great quantities of crustal material thereby generating the spectacular ______ Mountains. The Sheep Mountain Anticline is a fold generated during the Laramide mountain building event from 70 to 50 million years ago. large transform faults accommodate relative displacements of up to several ___ ____. Where oceanic lithosphere subducts beneath an oceanic plate, a _____ ____ ____ and related tectonic features develop. Seismic evidence suggests that a portion of the ______ subcontinent was thrust beneath ___-a distance of perhaps 250 miles. In addition to the pervasive regional metamorphism, numerous magma bodies intruded the crustal rocks along the entire _______ margin. This activity resulted in the piecemeal addition of crustal fragments to the entire Pacific margin of the continent --from Mexico's _____ Penisula to northern Alaska. NCALM Seed. Still other may have been submerged oceanic ______ created by massive outpourings of ______ lavas associated with mantle plumes. Small-scale deformation of rocks by shear stresses occurs along closely spaced parallel surfaces of weakness, such as ___ surfaces and _____ fractures, where slippage changes the shape of rocks. The two most common folds are _____ and ___. Mountain building has occurred in recent geologic past at several locations around the ___. True. A good example of topography that results when erosional forces attack folded sedimentary strata is found in the __, Valley and Ridge Province of the Appalachians. The Sheep Mountain anticline (Wyoming, USA) is a well-exposed asymmetric, basement-cored anticline that formed during the Laramide orogeny in the early Tertiary. Geologists have determined that one or perhaps more small crustal fragments were positioned on the _____ plate somewhere between _____ and ___. These major strike-slip faults are called ___ ____. Brittle deformation occurs when stress breaks the chemical bonds that hold a material together. Our simplified overview begins roughly ____ million years ago, with the breakup of a supercontinent called ____ that predates ______. @article{osti_6084236, title = {Surface and subsurface analysis of Sheep Mountain anticline, Wyoming}, author = {Abercrombie, S}, abstractNote = {The Sheep Mountain area, in the southwest Wind River Basin, is the up plunge closure of the Derby Dome-Winkleman Dome producing trend of an echelon folds which comprise the first line of folding down the northeast flank of the Wind River Mountains. Fault scarps are produced by rapid vertical slips that generate ___. Igneous and some metamorphic rocks (quartzite, for example) are composed of minerals that have strong internal chemical bonds. Anticlines in the basin provide subsurface structural traps for oil and natural gas, several of which produce from the Mississippian Madison Formation, a world-class fractured carbonate reservoir. In the stable ___________ of the continents, rocks reveal a history of deformation which shows that these areas were once sites of former mountain belts. Fracture network geometry was identified as a major control on fluid migration within the structure that has provided conduits for episodic hydrothermal fluid flow. Section 11.3 Faults and Joints: rock structures form by brittle deformation, form where brittle deformation leads to fracturing and displacement of Earth's crust, can be recognized in road cuts where sedimentary beds have been offset a few meters, large faults like the San Andreas Fault in California, have displacements of hundreds of kilometers of consist of many interconnecting fault surfaces. This sediment-laden basin contains thick ____ ______and debris eroded from the adjacent continental volcanic arc. The theory of ______ _____ provides a model for orogenesis with excellent explanatory power and accounts for the origin of virtually all the present mountain belts and most of the ancient ones. What is the nature of crustal fragments, and where did they originate? Although some joints have a random orientation, most occur in roughly parallel groups. The limb of an anticline is also a limb of the adjacent _____. Sierra Nevada, Coast Ranges, and Great Valley. Its NW–SE trend (Figure 1) is similar to that of many folds within the Rocky Mountains, although some others formed at acute angles to the regional compression [ Erslev, 1993 ]. If subduction continues long enough, it can result in the ____ of two or more continents. The surface sedimentary rock formations that are exposed in the fold, range in age from 66-360 million years. More than 100 of these relatively small crustal fragments, most of which are in the ____, are known to exist. Northwest. Island arcs result from the steady _____ of oceanic lithosphere, which may last for 200 million years or more. Similar to the breakup of Pangaea, this episode of continental rifting and seafloor spreading generated a new ocean between the _____ continental blocks. Salt domes are economically important rock structures because when ____ migrates upward, the surrounding oil-bearing sedimentary strata deform to form ____ reservoirs. With the collision of Africa and _____, the Appalachians, perhaps as majestic as the _____, lay in the interior of Pangaea. Because these newly formed basaltic magmas are less dense than the rocks from which they originated, they will ____ rise. is the force that acts to deform rock bodies, is the resulting deformation or distortion or change in the shape in the rock body. Field-based analyses of fractures and breccias were conducted to characterize structural elements of the anticline with respect to fluid flow. In addition from Chapter 6 that sheeting produces a pattern of gently curved joints that develop more or less parallel to the surface of large exposed igneous bodies such as ____. Geologists refer to the accreted crustal blocks as _____. The resulting wedge emerges to form the island of _____. came into existence 100 million years ago. JavaScript is disabled for your browser. __ may also be significant from an economic standpoint. This region, which is composed of relatively undeformed layers of sediment and sedimentary rocks, is called a ____ basin. Pollard Dept. Subduction along these active continental margins is associated with long-lasting magmatic activity that builds _____ ____ ____. In regions where sediment is plentiful, prolonged subduction may thicken a developing ______ wedge sufficiently that it ______ above sea level. Above the fault tip, the fluids circulated rapidly in the diffuse synfolding (and early folding) fracture network. However, large, thick units of oceanic crust, such as the Ontong Java Plateau, which is the size of ____, or an island arc composed of abundant light igneous rocks, render the oceanic lithosphere too buoyant to subduct. The rapid rate of seafloor spreading in the Pacific basin is balanced by a high rate of. By contrast, sedimentary rocks that are weakly cemented or metamorphic rocks that contain zones of weakness, such as _____, are more susceptible to ____ deformation. Along ____ plate boundaries, flat-lying sedimentary strata, tabular intrusions, and volcanic rocks are often bent into a series of wavelike undulations called ____. example of this close association are broad, regional features called monoclines. It is now known that many of the terranes that make up the North American Cordillera were scattered throughout the eastern _______, like the island arcs and oceanic plateaus currently distributed in the western Pacific. An outcrop-scale investigation of fracture geometry and geochemical analysis of breccia bodies in the anticline provides insight into the history of fluid migration and structurally-controlled diagenesis within the anticline. Thrust faults, on the other hand, exist at all scales, with some ____ thrust faults having displacements ranging from tens to hundreds of kilometers. These compressional mountains contain large quantities of preexisting ____ and ___ rocks that have been faulted and contorted into a series of folds. The major factors that influence the strength of a rock and how it will deform include, 1. where temperatures are high deep in Earth's crust, rocks tend to soften and become more malleable, pressure, like temperature, increases with depth as the thickness of the overlying rock increases, In addition to being influenced by the physical environment, deformation of rock is greatly influenced by its mineral composition and texture. These joint sets often exert a strong influence on other geologic processes. In Western United States, large normal faults are associated with structures called ____ ___ ___. Mississippian-age collapse breccia bodies were identified as preexisting weak horizons for focused hydrothermal fluid flow during the Laramide. Sudden movements along faults cause most _____. By contrast, the term terrain is used when describing the shape of the surface topography or "_____of the ____". Folds are geologic structures consisting of stacks of originally ____ surfaces, such as sedimentary strata, that have been bent as a result of permanent deformation. Sheep Mountain anticline is located on the eastern flank of the Bighorn Basin (Figure 1a), north central Wyoming, north of the town of Greybull. At some point, the forces that drive plate motions change, and a subduction zone develops along the margin of the _____. The photo shows the southwest end of the canyon cut by Bighorn River through the anticline’s core about 1/3 of the way along the ridge from its north end. Sheep Mountain is a classic example of a plunging anticline. Then, about 180 million years ago, this newly formed supercontinent began to break into smaller fragments, a process that ultimately created the modern ____ ___. The Sheep Mountain area, in the southwest Wind River Basin, is the up plunge closure of the Derby Dome-Winkleman Dome producing trend of an echelon folds which comprise the first line of folding down the northeast flank of the Wind River Mountains. Explore this 1.19 gigapixel image.44.649928, -108.198165 - Facing 360* The truck roughly marks the northern heading. The zone where two continents collide are ________ together is called a ______. Additional materials are derived from an adjacent continent or or ___ ___ and consists of volcanic debris and products of weathering and erosion. More model information This model shows the northern end of Sheep Mountain in central Wyoming. Sheep Mountain Anticline is a basement cored, doubly-plunging, asymmetric fold on the east limb of the Bighorn structural basin. buried, an environment where these rocks experienced elevated temperatures and pressures. The Mowry shale crops out in a SE-plunging syncline at the right. Hydrothermal solutions (mineralized fluds) can migrate into fractured host rocks and precipitate economially significant amounts of copper, silver, gold, zinc, lead, and uranium. When rocks are subjected to stresses that exceed their strength, they _____, usually by _____ or ___. For example, chemical weathering tends to be concentrated along joints, and joint patterns influence how groundwater moves through the crust. In simple folds, the ____ ____ is vertical and divides the fold into two roughly symmetrical limbs. Folds are also described by their ____ plane, which is a surface that connects all the hinge lines of the folded strata. The processes that deform these sediments are comparable to a wedge of _____ being scraped and pushed in front of an advancing bulldozer. Next, we will take a closer look at two examples of collisional mountains: The Himalayas , Earth's _____ collisional mountains, are still rising. Anticline. When an oceanic plate contains small seamounts, these structures are generally subducted along with the descending ______ slab. Take a look at the Big Horn River that cuts through the middle of Sheep Mountain. In addition, mountain belts of similar origin formed during the same period and were once ______ are found in the British Isles, Scandanavia, northwestern Africa, and Greenland. Section 11.7 What causes Earth's varied topography? Particularly, prominent features of the Colorodo Plateau, ____ are large, steplike folds in otherwise horizontal sedimentary strata. Because what are typically horizontal rock layers are here found tipped up and eroded what we were able to do as we hiked up the mountain was go through successively older layers of rock: we were hiking back through time. The blue line down the center of the fold represents the axial trace, or the line that separates the two dipping limbs of the fold. The Black Hills of western South Dakota is a large structural ____ generated by upwarping. Much of India is a continental shield composed mainly of ____ rocks. This has occurred along the southern end of the _____ _____ trench, where the Orinoco River basin of ____ is a major source of sediments. Folds of this type are said to _____ because the hinge lines of the fold penetrate Earth's surface. the limbs are mirror images of each other, one or both limbs are tilted beyond the vertical. These displaced crustal blocks include much of southeast Asia, region between India and China, and sections of ____. About ___ million years ago, for reasons geologists do not completely understand, plate motion changed dramatically, and this ancient ocean basin began to close. a fault in which the dominant displacement is horizontal and parallel to the trend (direction) of the fault surface is called a ___ ___. The continued closing of this ancient ocean basin resulted in the collision of a microcontinent with _____ ____. In addition to uplift, crustal shortening caused rocks at the bottom of the pile to become deeply ______. The final _____, called the ______ Orogeny, occurred between 250 and 300 million years ago, when Africa collided with North America. It is important to realize that ridges are not necessarily associated with _____, nor are valleys a characteristic of ____. Crustal shortening accommodated some of this motion. Movements along these faults produced alternating uplifted fault blocks called __, are tilted fault blocks, also contribute to the alternating topographic highs and lows in the Basin and Range Province. The slopes of the large normal faults associated with the Basin and Range Province decrease with depth and eventually join to form a nearly horizontal fault called a _____ fault. This doubly-plunging asymmetrical anticline is deeply dissected and exposes strata ranging in age from the Mississippian (Madison Formation) to the Paleocene (Ft. Union Formation). Geologically speaking, Sheep Mountain is an anticline which is a type of folded bedrock that has an arch-like shape with its oldest rocks at its core. Andean - type mountain building is characterized by _____ beneath a continent rather than oceanic lithosphere. an example from Sheep Mountain Anticline, Wyoming N. Bellahsen, P. Fiore, D.D. example: Sheep Mountain, Wyoming is an example of a plunging anticline A good example of topography that results when erosional forces attack folded sedimentary strata is found in the __ Valley and Ridge Province of the Appalachians which exhibits the opposite sense of displacement is a well known example of a left-lateral strike-slip fault. 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