Assignment 8-1 done

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Raritan Valley Community College *

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Geology

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Jan 9, 2024

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Assignment 8 – Geologic History of New Jersey Being a coastal state, New Jersey currently has multiple geologic environments that represent the physiographic provinces they lie within. Southern New Jersey makes up the coastal plain physiographic province and is represented by flat unconsolidated sediment thousands of feet thick. North of the coastal plains lie the piedmont and valley and ridge province which are represented by folded metamorphic and sedimentary rock, respectively. Part 1: Read the article “ The Geologic History of New Jersey’s landscape ” written by Scott Stanford, state geologist of the New Jersey Department of Environmental Protection. As you read, recall the information you have learned throughout this course to answer the below questions. 1. The Cohansey Formation tells us that much of southern New Jersey had which type of depositional environment 10-15 million years ago? What features of the Cohansey formation give us this information? (2 points) The Cohansey Formation is primarily consisted of unconsolidated, fine to medium-grained sands with interbedded clays, this shows that southern NJ used to be a lot like now being a coastal environment. The presence of cross-bedding and ripple marks in the sandstone layers suggests that the sediments were deposited by currents and waves. There has also been marine fossils that were found there, the presence of marine fossils indicates that the depositional environment had a connection to the sea. 2. What is the Beacon Hill Formation? What depositional environment formed this rock formation and what features of the Beacon Hill Formation give us this information? (2 points) The Beacon Hill Formation is a layer of iron-stained, sandy quartz and quartzite-rich gravel found throughout the New Jersey Coastal Plain, particularly in the Pine Barrens region. The Beacon Hill Formation is believed to have formed in a fluvial environment, deposited by a large river system. quartz and quazite gravel indicates that it was a river deposit. Aswell as the gravel noted to be stratified which is indication of moving water. 3. The Pre-Illinoian Glaciation reached as far south as Somerville. What glacial feature would we expect to find here 2.5 million years ago? What sediment characteristics would this feature have? (2 points) My grandma used to point out groups of rock and tell me that this was where the glaciers stopped near round valley and just around were we lived. I never believed it until I just found out that the glaciers actually stopped somewhere at somerville. The most prominent glacial feature is moraine. Morine is a landform composed of till, which is an unsorted mixture of various-sized rock fragments, clay, silt, and sand that is deposited by glaciers which marks the end of the glacier. Glaciers carry almost anything in its path so one of the most common sediment characteristics is called “Erratics” which are large isolated boulders kind of scattered around which is what what grandma showed me I think. Like th stratified gravel from beacon hill, the rocks typically show signs of Glacial Striations which are scrapes and

scratches that are left to the underlying bedrock 4. New Jersey has a rolling topography between New York and Trenton, what did this area used to look like prior to the Pre-Illinoian glaciation? What is responsible for its current topography? (2 points) The area was probably much more eroded than what we see today. The pre-glacial valleys were likely wider and deeper because the glaciers of later glaciations filled and narrowed the valleys with glacial debris. What we see in todays current topology relates to what happened awhile ago. The glacial processes during the Pleistocene Epoch had a profound impact on the landforms in the region. Including the biggest one bein g Glacial erosion, since glaciers wipe anything out and bring anything around, erosion sculpts the terrain into distinctive features. 5. Why is the Cape May Formation significant for a climate scientist attempting to educate people on the possible outcome of global warming? (2 points) The Cape May formation provides evidence of past sea level changes and the impact of warming temperatures on coastal ecosystems. The formation contains fossils of oysters and other marine organisms that lived in shallow water environments millions of years ago. The presence of these fossils at high elevations above present-day sea level indicates that sea levels have risen significantly over time. This rise is attributed to past warm periods when glaciers melted and released large amounts of freshwater into the oceans. During warm periods, the distribution and abundance of marine organisms changed significantly, indicating that ecosystems are sensitive to temperature changes. Using that information we can base an estimate on how our life could be impacted in todays age if there was a climate change. Part 2 : On the next page is a geologic map of New Jersey, use this map and the knowledge gained in this class to answer the following questions. 6. Which type of organism would you most likely find fossilized in Trenton during the Cretaceous Period? (hint: there are many correct answers, pick one that matches the likely depositional environment based on the sedimentary rock types) (2 points) The picture shows that the deposital enviorment in trenton was sand, silt, and clay which lines up with the Cretaceous period. Since the area was mainly sand, silt, and clay that means the area was consisted of river channels, floodplains, or estuarine environments. The most common organism to find would be marine invertebrates, Bivalves, and Gastropods. 7. Triassic sedimentary rocks are listed as “siltstone, shale, sandstone, and conglomerate”. Let’s assume the rocks are sequenced (from top to bottom) in that exact order . Why would it be impossible for sedimentary rocks listed in the exact same sequence for the Jurassic to be in that exact same order? Assume no unconformity exists. (hint, think about rocks deposited as sea level changes) (3 points) Imagine you're making a layered sandwich. Each layer represents a different type of sediment deposited over time. Now, for the Jurassic rocks to have the exact same order, it would be like trying to recreate the same sandwich, layer by layer, in the same sequence. But Earth's kitchen doesn't work that way.

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