User:Jbuskop/sandbox

Geology of New England

Proterozoic

During the late Proterozoic, rifting split Rodinia into Laurentia, Baltica, and supercontinent Gondwana. The Iapetus Ocean filled the rift basin between Gondwana and Laurentia. As Gondwana and Laurentia eroded, sediments flowed into the rift zone and accumulated, forming continental shelves on top of the Grenville gneisses.

Cambrian Period

Much of the N-S trending geology of Western New England is the result of thrusted continental shelf and off-shelf strata. Sandy sediments deposited on Gondwana's continental shelf are now the quartzites of the Plainfield and Cheshire Formations and Potsdam Sandstone. In the Champlain Valley of upstate New York, faulting is responsible for large (>80km) thrust transport of Proterozoic continental shelf strata. Outcrops of these far transported off-shelf facies provide evidence that they are part of the Taconic allocthon.

Ordovician Period

As Laurentia moved away from Rodinia, volcanic island arcs grew offshore. It is disputed whether the Bronson Hill or Shelburne Falls arc collided with Laurentia during the Taconic. Continental slope sediments have been metamorphosed into the Everett, Manhattan, Canaan Mountain, and Hoosac schists.

Champlain Thrust (NEIGC)

Trip B3: Faults of all kinds in the map of the Ordovician Champlain thrust zone around southern Lake Champlain

The Champlain thrust dips eastward beneath the metamorphosed Green Mountains. Current estimates of the displacement along the fault are 35 to 50 miles

"""The Green Mountain State is home to greenstones, green schists, green phyllites, green slate, greenschist facies metamorphism, green marble (verde antique) and the Green Mountains.

1. What are the types of green rocks in Vermont? Vermont has a variety of green to gray-green colored metamorphic rocks. It is home to green schists, phyllites, slates and metamorphosed igneous rocks such as metadiabase, metabasalt, and serpentinite (see the Belvidere Mtn page) or the Tibbit Hill metavolcanic (with big tan-weathered feldspar laths)The green color in all these rocks comes from green minerals such as chlorite, amphiboles, and epidote. The green minerals are sometimes referred to as mafic minerals or ferromagnesian minerals because they are comparatively high in iron and magnesium. Dark colored rocks with abundant ferromagnesian minerals are also referred to as mafic and even ultramafic rocks; light colored rocks higher in light-colored mineral such as quartz, feldspar and muscovite (eg. granite) are referred to as felsic rocks.

2. What is green schist? Green schist in Vermont is a metamorphic rock which has a foliation ( very fine layers) due to parallelism of platy minerals such as chlorite. The foliation may or may not be parallel to original sedimentary layering (bedding). In general, grain size decreases from schist to phyllite to slate. Green slate occurs mainly in southwestern Vermont whereas green phyllite and schist occurs closer to the Green Mountains.

3.What are greenstones? Greenstones are altered igneous rocks (ex. ancient volcanic rocks) which get their green color from chlorite +/- amphiboles and epidote. In Vermont these rocks may also be referred to as metamorphosed volcanics, pillow volcanics, pillow lavas, metaigneous rocks, mafic volcanics, metadiabase, metagabbro, amphibolite, and mafic schist. Yet all are metamorphosed igneous rocks of one type or another and the original parent rock type is not always known. The AGI Glossary of Geology defines greenstone (meta) : A field term applied to any compact dark-green altered or metamorphosed basic igneous rock (eg. spilite, basalt, gabbro, diabase) that owes its color to the presence of chlorite, actinolite, or epidote. In Vermont, the term greenstone has also been used to refer to metamorphosed sedimentary rocks derived from an igneous source.

4. What is greenschist facies? Metamorphism is a change of an original parent sedimentary, igneous, or metamorphic rock due to a change in temperature and pressure. Different minerals are stable at different temperatures and pressures; different mineral assemblages are associated with each facies. A facies diagram shows the different temperature and pressure fields for different metamorphic facies which from lower temperature and pressure to higher temperature and pressure are: zeolite, prehnite/pumpellyite, greenschist, amphibolite, and granulite. Greenschist facies temperatures are generally 350-500 degrees centigrade.

5. The Green Mountain Giant - a glacial erratic.""" could be good content to paraphrase

Article Evaluation: Champlain Thrust

Content

• Is everything in the article relevant to the article topic? Is there anything that distracted you?
  • Everything was relevant to the article topic, but was somewhat broad. The introductory paragraph addresses location and contains some broad characterization of the fault (general dip direction, but no dip angle) and the age of the rocks it is thrusting upward. The author notes the origin of the thrust (accretion from one of the island arc terranes during the Taconic) and notes a time of alteration (Acadian Orogeny) but lacks any specific evidence that supports these claims.
  • The article references one prominent exposure of Lower Cambrian dolostone thrusted on top of the Middle Ordovician Iberville shales in Burlington, VT, but fails to include any details about the exposed formation or depositional environment.
• Is any information out of date? Is anything missing that could be added?
  • Wiki cites a 2016 website from the University of Vermont, a 2002 GSA bulletin, and a 1987 GSA field guide. The last two sources lack links (would be helpful to have those)
  • Could use some more sources that might have info on depositional environment/sedimentology, more detailed structural geology notes.
  • Information from the B3 NEIGC field trip could be supplemented...
• What else could be improved?
  • Are there any effects of glaciation on the outcrop locations of the thrust fault?
  • Are there any competing ideologies on formation/which orogenies altered the thrust fault?
  • Wikipedia calls this type of article a stub, so serious improvements could easily be made. This article does not have enough information to be considered an encyclopedic entry.

Tone

• Is the article neutral? Are there any claims that appear heavily biased toward a particular position?
  • Neutral tone. Attributes formation to the Taconic Orogeny and reactivation to the Acadian Orogeny (which might be true).
• Are there viewpoints that are overrepresented, or underrepresented?
  • There isn't really one viewpoint, except for origin attributes. Broad facts only.

Sources

• Check a few citations. Do the links work? Does the source support the claims in the article?
  • The one hyperlink functions. Copy/paste of the other citations leads the researcher to the articles in google. Insertion of hyperlinks would be useful.
  • The Stanley (1987) article references a plethora of other sources that could augment the information found on the wiki.
• Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted?
  • the facts in the intro paragraph are referenced and they seem to be neutral sources, as far as geology goes.

Talk Page

• What kinds of conversations, if any, are going on behind the scenes about how to represent this topic?
  • The last edit was made in 2017 by user Frietjes. Many of the edits are minor changes to Wiki formatting and not a lot of content based contributions.
• How is the article rated? Is it a part of any WikiProjects?
  • Stub article: needs more information to become an actual encyclopedic entry. Related to Geology of VT category, Lone Rock Point page,
• How does the way Wikipedia discusses this topic differ from the way we've talked about it in class?
  • The article is similar to the way we discuss NE Geology in class because of it references orogenies we have read about, but could really use a geologic map, and more information on the intricacies of this specific thrust fault, and why it is so relevant in the study of NE Geology.

NCS Subsea work

== NCS Subsea Inc. == NCS Subsea specializes in UltraHigh-Resolution 3D Seismic (UHR3D) data acquisition using P-Cable.

Much of the geomorphology and surficial deposits of New England are a result of glaciation in the Quaternary period. The scoured New England landscape reveals evidence of the Wisconsin Glacial Period.

New England Geology 2017

Surficial Deposits

The continental ice sheet over New England was more than a mile thick in some places. Grinding and plucking over the landscape created wore down topography and created poorly sorted to well sorted surficial deposits. Large terminal moraines composed of poorly sorted till are present along coasts and can be identified by their thin, patchy, and stony texture . Maine is bordered by moraines that identify the terminus margins of the past ice bodies. The Waldoboro terminal moraine sits on the southeastern coast, while the Highland front moraine parallels the northwestern border. Large continental ice sheets (see Laurentide Ice Sheet) most likely created the large moraines, as it takes time for the long, lumpy ridges to form at a massive scale .

New England is best known for its high density of erratics, which are displaced rocks that differ from the immediate bedrock composition of the region and range from the size of pebbles to boulders. Their surfaces are generally rounded and polished due to rasping. While the bedrock of the area is largely igneous granite, the erratics are sandstone and slate blocks . Sedimentary erratics are visible across the highest peak in Maine, Mount Katahdin.

Glacial outwash that is well sorted and stratified due to the systematic nature of Stoke’s Law is visible in gravel pits in Maine's Grafton Notch State Park Outwash plains are composed of alternating layers of sand and gravel that have been deposited in deltas of glacial lakes and alluvial fans.

Erosional Processes

The slow and grinding movement of continental ice sheets and alpine glaciers across the landscape creates erosional landforms. Abrasion, plucking, and freeze-thaw action creates the U-shaped valley unique to glacial erosion.

The intense pressure from the ice causes abrasion. This process carves striations, or grooves, into the bedrock as the glacier moves down a slope. Glacial striations help determine the direction of a glacier; visible outcrops in the White Mountains, for instance, indicate ice flow toward the south-southeast . Abrasion also produces rock flour which is visible in glacial outwash plains across New England.

Maine has some of the longest eskers in the world . As the climate began to warm, the glaciers began to melt and drainage from meltwater under the glacier formed huge torrents of sediment that, when compacted, left a long and sinuous ridge or kame. Moose Cave in Grafton Notch is speculated to have been formed in part by a subglacial river . Abol esker in Baxter State Park is a notable serpentine kame.

Kame and kettle topography is commonplace across Maine. Hummocky morphology includes kettle ponds and kettle lakes that are “steep-sided, bowl-shaped depressions in glacial drift deposits” where large blocks of ice melted as the glacier recessed.

Other notable glacial features include Cirques. Mt. Katahdin and the Bigelow Range have circular divets indicative of glacial erosion.

Geology

Grafton Notch reflects the glaciation processes carved by the Laurentide Ice sheet during the Wisconsin Glaciation episode. Notable geomorphology of the park includes U-shaped valleys, gorges, and esker . Erosional processes expose the unique bedrock composed of Devonian granite with pegmatite intrusions . Poorly sorted diamicton and stratified gravel pits indicate glacial and glacio-fluvial depositional processes at work. Additionally, these processes scattered erratics over the u-shaped valley floor .

Noteworthy gorges in Grafton Notch include Screw Auger Falls, Mother Walker Falls and Moose Cave. Screw Auger Falls is located within a steep gorge along the Bear River; when water levels are low enough, erratics are visible in the stream . Steep cliff faces and flat valley floor seen from Mother Walker Falls are characteristic of glacial erosion. However, responsibility for gorge formation is debated; “they may have formed while the ice sheet retreated north of the region and contributed a large quantity of meltwater, or more likely, they formed while the ice sheet covered the area and the subglacial water was under very high pressure” . Whether a particular landform was created by local glacier or continental ice sheet is also still debated. Pegmatite vein intrusions are visible around the water eroded bedrock of the gorges.

A view of Moose Cave gorge in Grafton Notch State Park, Maine.

References

Screw Auger Falls in Grafton Notch State Park, Maine.

Borns, H.W., Calkin, P.E., 1977, Quaternary glaciation, west-central Maine, Geological Society of America, p. 1773-1784

Caldwell, D.W., 1998, “Roadside Geology of Maine,” Mountain Press Publishing Company, Missoula MT.

Department of Agriculture, Conservation & Forestry, 2002, Glacial and Postglacial Geology Highlights in the White Mountain National Forest, Western Maine: http://digitalmaine.com/cgi/viewcontent.cgi?article=1359&context=mgs_publications

Department of Agriculture, Conservation & Forestry, 2001, Glacial and Postglacial Geology of Grafton Notch State Park: http://digitalmaine.com/cgi/viewcontent.cgi?article=1346&context=mgs_publications

Doughty, A.M., Thompson, W.B., Grafton Notch State Park: Glacial Gorges and Streams under Pressure in the Mahoosic Range, Maine.

Thompson, W.B., and Holland, W.R., compilers, 1999, Hiram Quadrangle, Maine: Maine Geological Survey Open-File Report 99-85, scale 1:24,000

Geoarchaeology Wikipedia Article Evaluation

·       Is everything in the article relevant to the article topic? Is there anything that distracted you?

The subsection on Archaeological geology is distracting in the sense that it does not feel related to Geoarchaeology. Not enough substance is given to relate the two subjects, nor is there a citation for the definition.

·       Is the article neutral? Are there any claims, or frames, that appear heavily biased toward a particular position?

There don't seem to be enough citations for each technique in geoarchaeology. If you’re lucky, there is maybe one citation for each technique listed.

·       Check a few citations. Do the links work? Does the source support the claims in the article?

¾ of the in text citations lead to the original text. One link does not. A brief assessment of the abstracts leads me to believe the sources support the claims in the article.

·        Is each fact referenced with an appropriate, reliable reference? Where does the information come from? Are these neutral sources? If biased, is that bias noted? 

No, there are “facts” littered throughout the article lacking citations. Heavy assessment of the of information is needed to determine whether it can be trusted.

·       Is any information out of date? Is anything missing that could be added?

2 references are from 1980, and many are in German. This leads me to believe that perhaps one editor of the page was German, but these articles have not been assessed for validity.

·        Check out the Talk page of the article. What kinds of conversations, if any, are going on behind the scenes about how to represent this topic? 

There are no conversations about the article currently.

·       How is the article rated? Is it a part of any WikiProjects?

This article is part of the Archaeology and Geology WikiProjects and is of high importance to the Geology project. The article is rated as Start-Class on the project’s quality scale.