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// This artifact is my field report after a trip in my Physical Geology class with Professor Rayburn (GLG220-02). Geology is out of my major and originally served only as a general education requirement for me. However, once there I found a real appreciation for the knowledge and skills I gained in the class. This demonstrates “inquiry” and “intellectual growth” as I was at first resistant, but learned to love an entirely foreign discipline. //

//The field report is a crucial part of the geology discipline and is written in a very clear, scientific manner. I had to learn the correct style of writing to accurately explain the natural phenomena of the surrounding Hudson Valley. I could see this being very useful in class as it is simply another style of writing. One which could help students more scientifically-oriented enjoy writing and its scientific applications. I can see dozens of assignments and lesson plans where writing like this can be the target.//

Jason Weiss Professor Rayburn Physical Geology 11/21/2010 Field Trip Stop 1- Right on the banks of the Hudson we find an enormous deposit of Ordovician-aged sedimentary rock. The rock is composed of alternating beds of greywacke sandstone and shale, thus the Austin-Glen Greywacke. The alternation suggests an annual or semi-annual deposition of sediments. The graded bedding is actually the result of underwater landslides or turbidities. The presence of turbidities suggests a coastal, shallow sea. Therefore it would be highly unlikely to find fossils in such rock, as the water would be unable to support life or even attract it. The rock is also noticeably shifted. The greywacke is striking North-South and is dipping to west, while plunging to the east. Such figures indicate a significant tectonic event, in this case the Acadian and Alleghenian orogeny. The greywacke was formed during the Taconic orogeny and then deformed in such a manner during first the Acadian, then the Alleghenian. The deformation sequence is supported by the overall age of the rock combined with the style of deformation and the law of original horizontality. Also, as the beds get younger they begin to shrink in width, showing an increase in the landslide’s frequency. Further down the coast a basin is observable as a site of deposition for the Taconic orogeny. Finally, the sandstone retains ripples supporting an underwater landscape. Note in the picture faults along the beds and various joints throughout. Stop 2- This stop is a popular site for rock climbing, hiking, and other recreation activities- many of which are afforded by the geology! This outcropping consists of the Martinsburg Shale covered by the Shawangunk Quartz-Pebble Conglomerate. The shale is of the middle Ordovician and the quartz-pebble conglomerate is from the late Silurian. The age gap between these rocks shows a disconformity in the outcrop. Each rock has particular qualities that help paint a picture of the Hudson valley. The shale is striking to north-south and dipping to the west. The shale is quite weak and low on the Bowen’s Reaction series in terms of resistance to weathering. Atop the shale rests the conglomerate which is quite high on the Bowen’s reaction series in terms of resistance to weathering; thus resisting most forms of weathering and acts as a hard hat for the shale. Because of this interaction the cliffs tend to get steeper, until pieces of the conglomerate tumble down. The disconformity earlier mentioned is also supported by the fact that the shale was probably formed in a deep-sea environment, because shale consists of fine particles, and the conglomerate was formed in high-energy river environment with strong land-based erosion. Thus, we can see a geological regression, perhaps afforded by the rising of land due to orogeny. The particular orogeny in question is the collision of Avalonia and the continent. These factors are essential to creating the world renowned climbing spot. The hard and stable conglomerate is naturally great for climbing due to its practically naturally occurring handholds. Also, note that the shale was formed about the same time as the previous greywacke. Stop 3- This stop was in the town of High Falls at the Rondout Dolostone. As the name implies, this stop is at a waterfall and is not dissimilar from the Shawangunk conglomerate. A waterfall is water running over a harder rock sitting atop a softer rock. The combined rocks are weathered to a cliff and then the water spills off eroded the waterfall location further down river each year or nick-point migration. The harder rock is dolostone and the softer rock is composed of limestone, indicating a shallow marine environment. The overall age is Silurian period, thus the youngest of the first three stops. It is oriented in an east-west axis. Noticeably different from the waterfall, across the river is a shale monocline. The Highfalls shale is Silurian aged as well, but is indicative of a deep marine environment, as in the last stop. The shale is also strangely colored which shows oxidation, which in turn expects a shallow, rather than deep sea. Not far from the waterfalls there is a quartz sandstone anticline. The sandstone is known as the Binnewater sandstone and is Silurian aged. The anticline is plunging north and its composition expects a very shallow or even shore deposition. The Binnewater sandstone is older than the Rondout dolostone, which is the youngest. Currently the ages look like: dolostone, Binnewater sandstone, Highfalls shale, and the Shawangunk conglomerate.

Stop 4- The final stop is also the youngest stone on the trip, Devonian aged limestone. The limestone is arranged into a textbook example of an anticline and is composed of three beds of limestone layers atop each other; they range from oldest to youngest: Becraft limestone, Alsen limestone, and Port Ewen limestone. Once again the limestone suggests a shallow marine environment. Such an environment would be perfect for supporting a population of any multitude of creatures. Thus the Becraft limestone is extremely fossiliferous, containing brachiopods and crinoids. As the limestone gets younger the fossils begin to disappear, suggesting a dirtying of the water that pushed out fauna. Also note that the anticline is plunging and that the rock is weathered thanks to the expansion and contraction of water inside cracks in the surface. The big picture- The story begins with the Taconic orogeny. This tectonic event created the basin that would later become Austin-Glen greywacke. The basin was deep-marine, which allowed for the settling of fine particles into shales and greywacke sandstone. The outcrop has graded bedding which suggests the annual deposition of sediments thanks to underwater landslides. These rocks formed at the middle of the Ordovician. Next we find the Martinsburg shale underneath the Shawangunk Quartz-Pebble conglomerate. The Martinsburg shale is the about the same relative age of the Austin-Glen shale, thus we can infer this occurred during the Taconic orogeny. The conglomerate atop the shale, however, represents a disconformity between late Silurian and middle Ordovician. We know the conglomerate to have been deposited on land, by means of a high-energy river. This river would have disappeared with the rising of land during the geological regression provided by orogenies. Third on the trip is the town of High Falls and the dolostone waterfall found in the Rondout River. At this point we have the Highfalls shale, Binnewater sandstone, and Rondout dolostone deposited atop quartz conglomerate. The conglomerate was most likely placed there during the same tectonic event that moved the Shawangunk conglomerate. The limestone and dolostone are also Silurian aged and thus affected by the same orogeny. The shale, however, depicts a deep marine environment which suggests some tectonic event that could have forced the shale up from the seabed. Rounding out the epochs is the Devonian aged limestone found on route 9W. This outcropping is composed of fossiliferous limestone, thus it had to be shallow marine environment. The continual dirtying of the water suggests a geological regression in accordance with the Shawangunk conglomerate, as it will grow dirtier as it becomes more shallow. The overall findings provided by these outcrops suggest that Taconic orogeny was the first of a few to forcefully shove land up above sea level, displacing conglomerates and fauna alike.

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