Sedimentary Depositional Descriptions

Sedimentary Depositional Descriptions - Depositional...

This preview shows page 1 - 3 out of 6 pages.

Depositional Description of the Stratigraphy: Ghost Ranch, New Mexico By: Travis Thompson 5/16/15 1
Image of page 1

Subscribe to view the full document.

Triassic Lower Chinle Formation - The deposition of Triassic Lower Chinle (TRcl) occurred in a river environment roughly 220-228 million years ago, when the Ghost Ranch was only 10 degrees north of the equator. The lower Chinle is the oldest rock exposed here at the Ghost Ranch. The unit consists of white to tan to green stratified sandstone; that is coarse-grained quartz sandstone that locally contains abundant well- rounded quartzite cobbles. Triassic Upper Chinle Formation - The deposition of the Triassic Upper Chinle (TRcu) Formation occurred in a coastal plain environment of lakes and streams roughly 205-220 million years ago. The formation consists of colors of deep red with stripes of green, gray and purple. The formation consists of siltstone, shale, mudstones, and sandstone, and the uppermost unit of the Upper Chinle is a thin-bedded red-brown to gray brown siltstone/sandstone layer. Many fossils are found in the Upper Chinle, including the dinosaur Coelophysis . The Upper and Lower Chinle range in thickness from 600- 7 00ft. Period of Erosion (unconformity) - There is a significant gap in the rock record spanning roughly 44 million years between the late Triassic rocks of the Upper Chinle and the middle Jurassic rocks of the Entrada sandstone formation here at Ghost Ranch. Here represents a period of major erosion with no to minimal amount of deposition of sediment. Once the erosional forces begin to slow down or stop we begin to have deposition of what is now called the Entrada sandstone formation. Jurassic Entrada Formation - The deposition of Jurassic Entrada (Je) Formation occurred in an eolian (wind-blown sand) dune environment that blew towards the south- southwest. The even-grained sandstone Entrada consist of small to large cross bedding due to the large dunes covering the majority of the Southwestern United States, an environment comparable to the modern Sahara Dessert. The orangish/red, yellow cliffs just below the Todilto were laid down during the Middle Jurassic about 165-161 million years ago. You can see a beautiful outcrop of the pinkish-tan Entrada on the vertical cliffs of Kitchen Mesa. The Entrada ranges in thickness from 200-400ft. Jurassic Todilto Formation - The deposition of Jurassic Todilto Formation (Jto) occurred in an inland sea that flooded the Southwest in the late Middle Jurassic, an environment comparable to the modern Great Salt Lake. The unit consists of thin-bedded limestone overlain by light to dark grey irregularly distributed sections of gypsum. The grey limestone was formed in the inland sea. The white gypsum was formed in high saline waters through subsequent evaporation allowing for a precipitate to form. You can see can see the Todilto on the very top of Kitchen Mesa. Based on some fossil evidence the Todilto is believed to be 159 million years old. The Todilto ranges in thickness from 10-100ft.
Image of page 2
Image of page 3

{[ snackBarMessage ]}

Get FREE access by uploading your study materials

Upload your study materials now and get free access to over 25 million documents.

Upload now for FREE access Or pay now for instant access
Christopher Reinemann
"Before using Course Hero my grade was at 78%. By the end of the semester my grade was at 90%. I could not have done it without all the class material I found."
— Christopher R., University of Rhode Island '15, Course Hero Intern

Ask a question for free

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern