Western Cordillera

The Slate Belt bioregion is nested within the Great Valley Section of the Valley and Ridge Province that was formed by thrust and fault folding during the Late Ordovician period through and Late Paleozoic era.(Bailey,1992; Geyer, 1979;Van Diver, 1990). During this time Taconian

“A minority disputes this theory, arguing that other events-such as volcanic eruptions, sea-level changes or a series of impacts-were to blame for the spectacular loss of species that occurred at the transition between the Cretaceous and Tertiary periods…”

Gerta Keller, professor of geosciences at Princeton University, has recently conducted research on the Chicxulub asteroid in which she analyzed new core samples taken from the asteroid site (Botzer 2004). These samples indicate that the impact that occurred at Chicxulub actually predated the mass extinction of the dinosaurs, which occurred at the Cretaceous-Tertiary boundary about sixty-five million years ago. Keller claims that the Chicxulub impact occurred approximately 300,000 years before the extinction (Keller 2004). Although previous researchers estimated that the Chicxulub asteroid was the cause of the extinctions, there had always been doubts about the exact age and size of the crater, and about the origin of the “mega tsunami deposits” that were located within the crater (Keller 2004). The focus of Keller’s recent research was on finding some answers to these questions. To do so she analyzed Cretaceous limestone, dolomite, and anhydrite deposits as the site of the Chicxulub crater (Keller 2004).

He narrowed his hunt down to a location in Denmark, where he had sent a colleague to perform an iridium analysis test at ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). When the results came back, Alvarez knew that whatever happened had not been a small-scale disaster. Once again, Alvarez was back to asking questions. What caused the increased iridium levels at the KT boundary? Except this time, he realized that his observations supported the ten year old hypothesis that had been proposed by paleontologist Dale Russell and physicist Wallace Tucker ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). They brought up the possibility of a supernova being the cause of dinosaur extinction. Supernovas are known to release high amounts of iridium, so such a hypothesis fit perfectly with Alvarez’s team’s discovery. However, the hope of having found a conclusion was short-lived. Luis Alvarez had mentioned that if said supernova had occurred that it would have released amounts of plutonium which would have been found alongside the iridium; no plutonium was found at either site. After more digging, the team came up with a new hypothesis ("Asteroids and Dinosaurs: Unexpected Twists and an Unfinished Story," n.d.). Perhaps an asteroid had struck Earth towards the end of the Cretaceous period, blowing enough dust into the atmosphere to

Florida and Shenandoah National Park have many commonalities as well as differences that makes each of these geologic setting unique. Though North America looks like Florida and Shenandoah National Park never seemed to collide with one another, Shenandoah has a rock record of being about 1 billion years old that constructed the North American continent and a building block that formed the Appalachians through orogenies. Florida falls about 300 million years old with the North American plate, however findings that were part of Gondwana provides evidence of the origin of Florida. With a vast time difference of these rock records, what can be furthered analyzed of what the

The Mesozoic tectonic history of the North American Cordilleran region is very complex and involves:

First, we must examine the sedimentary formations; when they were formed, how they were formed, and what materials they consist of. About ninety-three to one hundred million years ago, the Western Interior Seaway rolled through the North American continent, eventually reaching the geographical area of today’s Mesa Verde National Park (National Park Service 2005). This sea deposited a thick, hard sandstone base that is called Dakota Sandstone, although this layer is not exposed in the park

One of the major things noticeable from the cross section is that quite a few of the rock layers are over turned, where the older rock layers are above the newer rock layers. This is seen in the contact between the Quartz Monzonite of Papoose Flat and the Campito Formation which is also a disconformity. Next there is some fault zones separating the Camptio, Poleta, and Harkless formations. We then see some more overturned layers with the contacts between Saline Spring Valley Formation (lower and upper members) above the Mule Spring Formation along with some inferred folding. With a normal fault separating the inferred folding event, we see where the overturning occurs. In between the Cambrian layers we see Tertiary Basalt nonconformities also being folded, thus with that we know that the folding event was more recent than the formation of the Basalt. Next there is a large Basalt field with a spot of the Harkless formation. Again we see over tuning as the Basalt field ends there are the Devonian and Mississippian rock Layers on top of the basalt. Separating these overturned layers from the Harkless Formation and the Saline valley Formation (upper member), which are not overturned, is a thrust fault. From this information, there was a major stress event sometime after the Tertiary period causing the rock layers to fold and overturn. And from this stress event and from the folding, normal and thrust faults are formed. Finally we see that there were alluvial and landslide deposits from the Quaternary after the folding, faulting, and over

The land rose up and created a precipitous eastern edge of the batholith and a gentle western edge. 10 million years ago, uplift, which is the vertical rise of Earth’s surface due to natural causes, started to occur and accelerated quickly. Soon, the Sierra Nevada Mountain Range that we know today towered 14,000 feet in elevation. Throughout uplift, cracks formed in the granite of the mountains. They formed due to the pressure that came with the uplift. The erosion that stripped away most of the overlying rocks caused the remaining rock to expand and crack. These cracks are still forming today and they provide a template for future erosion.

Analyses from 7,300 years ago at the Hawken site in northeast Wyoming do not match with the hypothesis of a dry Altithermal, though this may be limited to the site from which the data was collected, and not representative of the entire High Plains area (Lovvorn, Frison, and Teiszen 2001).

The South Brae oilfield is mainly Kimmeridgian to mid-Volgian in age, however on some accounts it may possibly be of Oxfordian (Turner et al, 1987). The oilfield is heavily developed along the western, fault-bounded margin of the South Viking Graben approximately 161 miles NE of Aberdeen flanking Fladen Ground Spur (see Fig.1). The Upper Jurassic rifting of the South Viking Graben encountered, pronounced movement along the western bounding fault as syn-rift extension proceeded (Harris & Fowler, 1987, Gregory et al, 2007). Syn‐tectonic deposition throughout the Jurassic ensued the formation of a distinct sediment wedge thinning eastwards into the basin, outlining the main phase of fault movement down the boundary fault (Roberts, 1991). As a result, the Brae oilfields are a series of

The age of the thrusts and the areas where they occurred are dated to varying ages with the oldest tectonic action dated 595 million years ago to the youngest at 265 million years ago (Hatcher, R). The thrust faults in the center of the Blue Ridge area would appear to have the highest grade of metamorphism while the faults to the edge have the lowest grade metamorphism or sedimentary features (Hatcher, Robert, and Arthur Merschat.). this is easily seen because the area where the

Another rifting phase started in the early Jurassic around Pliensbachian or Toarcian (Chongzhi et al., 2013; Geoscience, 2014; Tindale, Newell, Keall, & Smith, 1998). Exmouth, Barrow, Dampier and Beagle Sub-basins were created until Middle Jurassic (He, 2002; Tortopoglu, 2015) and oceanic crust was laid down to form the Argo Abyssal Plain in Late Jurassic around 164-160 Ma during the Callovian to Oxfordian then followed by the Gascoyne and Cuvier Abyssal Plain in Early Cretaceous around 125 Ma (Fullerton, Sager, & Handschumacher, 1989; Müller, Mihut, & Baldwin, 1998). Passive margin was established in North West Shelf. Rifting phase of the basin transformed into sagging phase post breakup thermal subsidence when Gondwana breakup took place during Valanginian early Cretaceous around 134Ma. During the Campanian late Cretaceous, rifting along the Australian southern margin triggered the basin inversions and wrench reactivation of basin structures on NW Shelf. These movements arose the Barrow Island above sea level and formed Novara, Resolution and Exmouth Plateau Arch in Barrow, Dampier Sub-Basins and Investigator Sub-Basin (Figure 1) (Longley et al., 2002; Sinhabaedya,

At the beginning of the Tertiary, there is a layer of andesite breccia -a fast cooling extrusive rock that has not traveled far from its original deposition. This indicates a volcanic depositional environment. This formation was then intruded by intrusive slower cooling rocks that create a noncomformity between it and the Walker formation. The tuff breccia in the Walker formation is consistent with the same depositional environment as the andesite breccia formation as they are both extrusive rocks. It is possible that there was an eruption from a volcano that deposited the highly viscous andesite rocks followed by slower falling ash, which was then

In the middle of the eighteenth century, James Hutton proposed a theory, uniformitarianism; “the present is the key to the past”. It held that processes such as geologic forces- gradual and catastrophic-occurring in the present were the same that operated in the past. (Matt Rosenberg, 2004) This theory coincides with the theory of Continental Drift that was first proposed by Abraham Ortelius in December 1596, who suggested that North, South America, Africa and Eurasia were once connected but had been torn apart by earthquakes and floods. He also discovered that the coasts of the eastern part of South America and the