Geology Of The Oaks Belt

Shale becomes more predominate at near the top of the formation (Thompson 1970b). Thompson noted that this formation is largely composed of micrite, pelmicrite, and pelsparite, with a significant portion of dolomite also present (1970b). Indications of paleosol formation, sub-vertical burrows, and, in the clay-rich layers, abundant hematite flakes are common of Juniata sediments (Davies 2010 and Thompson 1970b). Each of the three genetic units in this formation, however, have unique lithologic compositions and sedimentary structures (Figure 2).

According to Thompson and Turk (2011), there are two types of igneous rocks—extrusive and intrusive—and the primary difference between the two types of igneous rocks is that the rocks are formed in two separate locations: within the Earth’s crust and on the Earth’s surface (35). Extrusive igneous rocks form when “magma rises all the way through the crust to erupt onto Earth’s surface” (35). Since the crystals do not have much time to grow, extrusive sedimentary rocks, also commonly known as volcanic rocks, have “fine-grained textures, with crystals too small to be seen with the naked eye” (Thompson & Turk, 2011, 36). For example, basalt is a common very fine-grained volcanic rock. On the other hand, intrusive igneous rocks form when

The youngest of these rocks are dated at about 220,000 years ago. Rhyodacties and quartz latites in the modern caldera area extruded from about 320,000 years ago to 260,000 years ago, and then silica-rich rhyolites at Glass Mountain northeast of the caldera erupted from about 210,000 years ago to 80,000 years ago. The scattered distribution of the initial mafic eruptions indicates that they were erupted from the mantle, while the slightly younger domes and flows were from a deep-crustal source. The youngest rhyolite eruptions erupted at the northeast rim of the caldera at Glass Mountain and were the first activity of the silicic Long Valley magma chamber (Bailey, et. al., 1989).

Next, we can see that the rock displays a subtle porphyritic texture with plagioclase comprising the phenocrysts. The overall texture of the surrounding groundmass is granoblastic equigranular. Under thin section we also see a weakly defined foliation evidenced in the preferential alignment of actinolite grains and to a lesser extent chlorite grains. Undulose extinction is also observed in quartz indicating the rock was subject to deformation. The normalized quartz, alkali-feldspar, and plagioclase (QAP) values of this rock indicate that it is classified as a grano-diorite according to the IUGS QAPF classification system which is consistent with the hand sample interpretation.

As I looked out the window, I saw walls of rocks all over the place. I also saw a lot of good rock exposure on the top of the mountain where the rock was to steep for the snow to stick to. You will notice that Mount Baker has an abundance of all sorts of rocks. From the rocks I examined I observed a lot of extrusive igneous rock, metamorphic rock and sedimentary rocks and you will find few places where you can walk continuously from shale or basalt into well-metamorphosed gneiss (Tabor & Haugerud). I observed rocks such as gabbro, shale, and types of extrusive and intrusive igneous rock such as basalt. The ages of the rocks range from about as old as the mountain, which is about 140,000 years old.

Complete this week’s lab by filling in your responses to the questions from Geoscience Laboratory. Select answers are provided for you in red font to assist you with your lab work. Although you are only required to respond to the questions in this worksheet, you are encouraged to answer others from the text on your own.

On the first side of the outcrop the rock when examined was greenish and had small black grains indicative of diorite with hornblende giving the green color. The rock was similar to the outcrop encountered at Hollow rock which also had several fractures parallel although not as many, and that outcrop was also highly weathered. On the other side of the outcrop, the rock was incredibly different. This side was not weathered beyond recognition but

Extrusive rocks form when magma reaches the Earth’s surface. Basalt is the most common extrusive rock, though rock that forms from the hardened magma is called intrusive. In the southwestern part of Colorado ash tuffs cover thousands of square miles. The tuff is created from the volcanic landscape. The Garden of the Gods for example, is made from extrusive rock. There are different types of rocks up there that are

It is subdivided, from north to south, into the Wabigoon, Quetico, Wawa, and Minnesota River Valley (MRV) subprovinces (Figure 2, Jirsa et al., 2011). The Wabigoon subprovince is composed of greenschist facies mafic volcanic and volcaniclastic rocks intruded by granitoid batholiths. Algoma-type iron formation and small mafic intrusions are also common in this terrane. Amphibolite to greenschist facies rocks comprise the majority of the Quetico subprovince. In Minnesota, it occurs as a westward thinning belt of relatively homogenous metasediments and interstratified migmatites. The Wawa subprovince is composed of greenschist facies mafic and felsic volcanic rocks, granitoid batholiths and subsidiary Algoma-type iron formation. The MRV is the oldest of the terranes, and is characterized by granulite facies gneissic domes (Jirsa et al., 2011). Although not included as part of this study, a comprehensive overview of the mineral potential of the Vermillion Greenstone (Wawa Terrane in MN) was provided by Peterson

Majority of the Canadian Shield is made up of metamorphic and igneous rocks. The rocks

mafic rock, with predominance of mafic minerals pyroxenes, olivines and calcic plagioclase; these rocks (example, basalt) are usually dark colored, but not always, and have a higher density than felsic rocks. ultramafic rock, with more than 90% of mafic minerals (e.g., dunite)

All of the volcanic and metasedimentary rocks are metamorphosed, whose grades are extending from greenschist to upper amphibolite, characterized by low-pressure but high-temperature (Isachsen & Bowring, 1994). The influence of basement fracture zone is reflected in the homoclinal and abruptly alternated trends of the volcanic belts, which is more frequently found in the southwestern domain of the province, while north belts show angular patterns (Fyson & Helmstaedt, 1988; Padgham,1992; Padgham & Fyson, 1992). Except for the sharp dips of the volcanics, regional-scale folds, foliations and cleavages over several successions shown in the metasedimentary rocks are studied to understand the deformation and metamorphism (Isachsen & Bowring, 1994). Fyson & Helmstaedt (1988) compare three major types of folds which are ranked by their ages and sizes from oldest, most extensive F0 to minor-sized, cleavage-foliation-associated S3 folds with intermediate type F1 between them and they suggest that the parallel trend and they suggest both foliation and folds are results of syntectonic

The Raton-Clayton volcanic field is about 20 000 km2 in size, and has been active periodically for the past 9 million years. The area is filled with peaks, cones, and lava-capped mesas. The mesas developed as lava flowed into valleys and depressions, cooled off and formed a resistant top layer over sedimentary rocks. As the surrounding rock eroded, the lava protected the underlying stratigraphy from erosion. This caused todays topography, where that which was once the lowest point, is now the highest. There is some disagreement over why the volcanic field is here, one possible cause is that it is near the end of the Jemez Lineament, which has numerous volcanic centers along its reach, possibly

The Blue Ridge Mountains sit within a larger tectonic area that includes part of the smoky mountains and Appalachian mountain chain. The Blue Ridge Mountains sit upon a large thrust plate area that has experienced repeated movement in the orogeny process as the Appalachians were built. This process occurred during the Proterozoic to the Paleozoic period (Tectonic Setting of the Southern Appalachians). Evidence of the faulting includes sedimentary zones at the end of the thrust. Within the thrust areas is high-grade metamorphic rocks and some igneous rocks from intrusion during collision events (Hatcher, R). Evidence of the intrusions are the dikes which can be seen and the large granite facies throughout the area (Grant, Willard).

Many petroglyphs, animal fossils, and artifcats are visible throughout this formation in addition to the exposed, petrified logs. Chinle is broken up into smaller members and from oldest to youngest they are- Mesa Redondo Member, Blue Mesa Member, Sonsela Member, Petrified Forest Member, and Owl Rock Member. Each member is made up of unique materials that are responsible for their remarkable color. The Paleozoic sandy conglomerate and siltstone of Mesa Redondo Member is red, yellow and purple and was once part of the river’s floodplain before its deposition between 225-227 million years ago. The Blue Mesa Member consists of multicolored mudstone cobbles in blue, green, grey, and purple colors and dates to 220-225 million years ago. These older members make up the badlands of Petrified Forest and display their colorful banding. The 216 million year old Sonsela member includes a few smaller bedded areas with brown cross-bedded sandstones, more multicolored mudstones in blue, grey, and purple, white and grey sandstone beds, and white cross-bedded sandstone conglomerates with an assortment of sizes for cobbles. The Petrified Forest member, an area within the Painted Desert feature, is approximately 213 million years old with thick red and brown mud and sandstone layers. As one would guess, this member contains a good majority of the fossilized wood segments and uranium-bearing minerals that are often present with such organic matter as trees and logs. At 205 million years old, the youngest Owl Rock Member represents an area where there had once been a dry inland lakebed, leaving observable trace minerals from the evaporation process. The colors found here are typically light to dark red with orange and white, resulting from the mudstone littered with thin layers of limestone throughout. The wide variety of color