Natural History: Determining the Age of Rocks and Fossils

    C.grains of sand-sized particles.     D.gypsum.   Answer Key: A   Feedback: The correct answer is A. silica.     Question 19 of 33 3.03/ 3.0303 Points Which of the following is a diagnostic feature of Specimen #16?

The collection of the rocks was based on just picking up the most amount of difference looking rocks that was possible and bringing them home to analyze. This was done for about two months from many difference locations including campgrounds, beaches, rivers, highways as well as construction sites. After about two months there were many rocks so I started to analyze and take out the rocks that were of the same kind. I found many granite, basalt and conglomerate rocks.

1 What is coal? Coal is a substance we consider today a fossil fuel, created from all the dead plants millions of years ago. Coal is formed from prehistoric plants that when they die are not able to release the energy they built up from photosynthesis Typically the plants had fallen into large swamps and bogs, and then over time the dead plants lying on the bottom of the swamps and bogs were slowly covered with other dead plants and sediment build-up. Once buried the plants were subjected to high amounts of pressure and temperatures, which over long periods of time it becomes peat then eventually creates coal. We refer to coal as a “fossil fuel” today because it is created from prehistoric plants and the coal we have today has been millions of years since it was in plant form. Today we coal is still being created we just don’t fully recognize it because how long the process actually takes.

Approximately 17 meters thick, Unit A defines the lowest third of the Juniata Formation. Fragments of marine fossils, including bryozoans, brachiopods, and gastropods, are commonly found in the bottom-most portion of this unit of structureless mudstone and quartz arenite. Quartz grains in the sandstone beds of Unit A are typically immature and fine-grained, though the sandstone packages tend to coarsen upwards. Though typically structureless, intermittent bedding of the sandstone and shale packages is observed in this unit, and some areas display

Next, these rocks undergo erosion, which is the process of moving sediments from one place to another. Then, these sediments are deposited all at one place and over time they start to converge and cement as layers which are also known as strata. As time keeps going, new sediments deposit and cement together over old ones forming new layers. This is a repetitive process that eventually build up layers to make up a Sedimentary rock. Approximately 40 major sedimentary rock layers exposed in the Grand Canyon National Park area range in age from about 200 million to nearly 2 billion years old. As you can see, sedimentary rock formation takes an excessive amount of time.

Quartz is the most abundant single mineral on earth. It makes up about 12% of the earth's crust, occurring in a wide variety of igneous, metamorphic and sedimentary rocks.Quartz varieties are commonly separated into two groups based on the size of the individual grains or crystals. Macrocrystalline quartz in which individual crystals are distinguishable with the naked eye, and cryptocrystalline quartz in which the individual crystals are too small to be easily distinguishable under the light microscope. Some of the verities of the Macrocrystalline quartz are

Tour guide Cheri Chantz provided a background on how coal and the mine itself were formed. The Coteau Freedom Mine was formed over 50-60 million years ago. It takes approximately ten feet of vegetation under heat and pressure forms approximately one foot worth of coal. The type of coal found at the Coteau Freedom Mine was lignite coal, which is a low quality form of coal. Lignite coal has lower energy content or BTU compared to other forms of coal due to the decrease in the amount of carbon present in the coal and an increase in impurities and water content. In fact, lignite coal is nearly one-third water.

Conglomerate is a sedimentary rock that consists of rock fragments, many of which are visible to the naked eye (Fig. e The rock cycle states that sedimentary rocks are formed through the compression of sediment, and conglomerate contains minerals and rock that have been compressed, providing visual evidence of the rock cycle (Rocksandminerals.com, 2013).

Starved Rock State covers about 200 miles and some 470 million years, from Ordovician sandstones to Pleistocene glacial till. The Ordovician St. Peter Formation sandstone was deposited across the midcontinent during the second major marine transgression of the Paleozoic Era. The first transgression deposited Upper Cambrian to Lower Ordovician clastics and carbonates. The clastic to carbonate rock transition is consistent with gradual sea level rise over the North American craton. Sea level dropped late in the early Ordovician, exposing the carbonate strata to processes of cave development.

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.

Coal is a sedimentary material the amount of pyrite in coal is related to the amount of disposal organic material that was compressed and formed

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

Lyons sandstone can be divided into two distinct types which are the red and grey facies. The red facies are the red- colored sandstone which contains no hydrocarbons and the gray facies are the white to black- colored sandstone which contain hydrocarbon in its matrix (Levandowski,

Weathering, geologic processes such as erosion, and climatic shifts allow for this immense desert ecosystem to continually evolve and change which has taken place for millions of years. This geologically wealthy environment is composed of alternating flat-lying layers of soft and hard deposits of mostly sedimentary rocks. Interchanging slopes and cliffs along the landscape helped form these layers of rock which can be seen fully exposed in areas of the mesa. Deposition of this landscape mainly occurred during the Permian, Pennsylvanian, Triassic and Jurassic time periods. The assortment of warm hues of sandstone were produced by varying levels of iron oxide minerals during formation.

     Igneous rocks are classified first by texture. This is broken down mainly into grain size. First there are intrusive, or plutonic igneous rocks. These types of rocks cool within the crust and forms large, visible crystals. The opposite would be extrusive, or volcanic rocks. These cool at the surface rapidly, forming small grains. A combination