keyboard_arrow_up
School
Brooklyn College, CUNY *
*We aren’t endorsed by this school
Course
MISC
Subject
Geology
Date
Dec 6, 2023
Type
Pages
18
Uploaded by KidUniverse16706
INTRODUCTION
: Sedimentary rocks form when sediments, rock fragments, minerals, or organic materials are deposited, compacted, and then cemented together. Sedimentary grain should undergo many processes such as erosion, deposition, compaction and cementation in order to turn into a sedimentary rock. Erosion is the destructive process in which water or wind loosens and carries away fragments of rocks. Deposition is the process by which sediment settles
out of the water or wind that is carrying it. Compaction is the process by which sediments are pressed together under their own weight. Cementation is the process by which minerals crystallize and glue particles of sediment together into one mass. Sedimentary rocks divide into four major types: Clastic Sedimentary Rocks, Chemical Sedimentary Rocks, Biochemical Sedimentary Rocks, and Organic Sedimentary Rocks. Clastic rocks are sedimentary rocks that form when rock fragments are squeezed together under high pressure. Chemical rocks are sedimentary rocks that form when minerals crystallize from a solution. Biochemical rocks are formed from shells and bodies of underwater organisms. The living organisms extract chemical components from the water and use them to build shells and other body parts. Organic rocks form where the remains of plants and animals are deposited in thick layers.
CONCLUSIONS
: In conclusion, in this lab I learned how and where the sedimentary rocks are formed. I learned a lot about different types of sedimentary rocks and how to identify them based
on their different characteristics such as color, grain size, shape, etc. I also learned about different
sedimentary environments in which sediments are formed and founded. Activity 6.3 A: Analyze the sedimentary rocks in Fig. A6.3.1. Below each photograph, describe the rock briefly, using your observations of its apparent composition (what it is made of), texture (the size, shape, and arrangement of its parts), and anything else you notice that might help you to interpret the rock.
The rock is made of rounded mineral/rock grains and is a poorly sorted mixture of sand and gravel, with the grains randomly arranged. The rock is made of gravel-sized rounded shell fragments that are randomly arranged.
The rock is made of cubic crystals halite that are randomly arranged and intergrown.
The rock is made of very fine-grained sediment and appears to be layered.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
The rock is made of layered fine-grained sediment, and includes fossil ferns.
The rock is made of quartz sand and shows no layering at the scale of the hand specimen.
Activity 6.3 B: REFLECT & DISCUSS
Reflect on your observations and descriptions of sedimentary rocks in part A. Then describe how you would classify these rock specimens into logical groups. By observing the sedimentary rocks I would classify these rocks into groups according to their color, texture and grain size. Rocks 1 & 2 have orange color, while rocks 4, 5, & 6 have grayish colors. Rocks 1, 2 & 3 can also be in one group according to their grain size, while 4 & 5 can also be in one group because these rocks are fine grained.
Activity 6.4 A:
Look at Fig. A6.4.1. A rockfall from one of the steep granitic walls of Yosemite Valley (A) caused boulders as large as 2 meters in diameter to crash down into the forested slope below (B). Eventually, these sediments might end up in the steep channel of a local stream (C) on their way to the Merced River (D), which flows through the main part of Yosemite Valley.
1.
Rockfall deposit close to the source area (Photo B). (a) List all of the grain sizes that you see or that are likely to be present in the rockfall deposit shown in photo B (also refer to Fig. 6.2). The largest sediment grain in B is approximately 2 m long. Use the grain-size class names listed in Fig. 6.15. The likely grain sizes present in the rockfall shown in photo B are gravel, boulders, pebbles, sand, and silt. (b) How would you describe the sorting of sedimentary grains in the rockfall deposit? Use the terms in Fig. 6.16A.
The sorting of sedimentary grains in the rockfall deposit can be described as poorly sorted. (c) How would you describe the shape of sedimentary grains you can see in the rockfall deposit? Use the terms in Fig. 6.168. The shape of sedimentary grains in the rockfall deposit can be described as very angular.
(d) If the sediments in the rockfall deposit were lithified together as they currently rest, without any further movement downslope, what kind of sedimentary rock would they form?
If the sediments in the rockfall deposit were lithified together as they currently rest they would form a conglomerate.
2. Tributary stream just downslope from rockfall deposit
(Photo C). (a) The large sedimentary grains that can be seen in the stream channel are generally less than~1.5 m in diameter. Judging from the turbulence of the mountain stream, what grain sizes do
you expect to be carried (suspended) in the water?
I expect grain sizes such as sand and silt to be carried in the water. (b) What grain sizes do you expect to be rolling, sliding, or resting on the bottom of the channel,
including those that you can see?
I expect gravel to be rolling, sliding, or resting on the bottom of the channel. (c) How would you describe the shape of the sedimentary grains you can see in or near this stream channel (Fig. 6168)?
I would describe the shape of sedimentary grains to be subangular. 3. River deposits exposed in the eroded bank of the Merced River (Photo D). (a) List all of the grain sizes that you see or that are likely to be present in the Merced River bank
shown in photo D.
The likely grain sizes present in the rockfall shown in photo D are sand and silt. (b) How would you describe the sorting of sedimentary grains in the stream bank?
The sorting of sedimentary grains in the stream bank can be described as poorly sorted. (c) How would you describe the shape of sedimentary grains you can see in the stream bank?
The shape of sedimentary grains in the stream bank can be described as subround. (d) If the sediments in the stream bank were lithified, what kind of sedimentary rock would they form?
If the sediments in the stream bank were lithified, they would form a conglomerate. (e) How would you describe the change or evolution of sediments between the tributary streams and the main Merced River? The change of sediments between the tributary stream and the Merced River can be described as the sediments became rounder and smaller over time. 4. Use your observations to make predictions
. The Merced River flows from Yosemite Valley at an elevation of -1,200 m above sea level in central Yosemite Valley to an elevation of 250 m where the river enters Lake McClure, a reservoir in the San Joaquin Valley west of Yosemite
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Valley. The actual distance the river travels along its channel from Yosemite to the upper end of Lake McClure is more than 65 km. You can examine the Merced River course between latitude 37.72°N, longitude 119.63 W (central Yosemite Valley) and 37.602°N, 120.100 W (inlet to Lake McClure on the Merced River) using Google Earth.
(a) What sedimentary grain sizes are likely to be deposited in Lake McClure from the erosion of Yosemite Valley?
Silt and clay are most likely to be deposited in Lake McClure from the erosion. (b) What do you think will be the composition of most of the sedimentary grains deposited in Lake McClure from Yosemite Valley?
I think the composition of the most sedimentary grains will be particles of the minerals in granite.
Activity 6.4 B: REFLECT & DISCUSS Based on your work, write a brief description of how the
clastic sediment from Yosemite Valley might change as it travels downstream to Lake McClure. Then describe how you could use these insights to interpret clastic rocks in general.
The clastic sediment from Yosemite Valley might become smaller, smoother, and rounder as
it travels downstream to Lake McClure. These insights about the change of rocks can help to classify clastic rocks based on their grain size, shape and sorting. Activity 6.5 A: Complete parts 1 through 6 for each sample in Fig. A6.5.1. Refer to Figs. 6.15, and 6.27 as needed. Sample A
1.
Grain size range in mm: ~0.2 mm to ~1 mm
2.
Percent of each Wentworth size class:
clay: 0 % silt: 0
% sand: 100
% gravel: 0
%
3.
Grain sorting (highlight):
poor moderate well
4.
Grain roundness (highlight):
angular subround well rounded 5.
Sediment composition (highlight):
precipitated siliciclastic bioclastic pyroclastic 6.
Describe how and in what environment this sediment might have formed. This sediment
consists of ooids that are typically associated with well agitated sands in a shallow submarine shoal, near-beach, or even lake environment. Sample B
1.
Grain size range in mm: ~0.5 mm to ~1 mm
2.
Percent of each Wentworth size class:
clay: 0 % silt: 0
% sand: 100
% gravel: 0
%
3.
Grain sorting (highlight):
poor moderate well
4.
Grain roundness (highlight):
angular subround well rounded 5.
Sediment composition (highlight):
precipitated siliciclastic bioclastic pyroclastic 6.
Describe how and in what environment this sediment might have formed. The sediment is composed of one mineral quartz meaning this sediment may have formed somewhere that it would be only slightly eroded. Sample C
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
1.
Grain size range in mm: ~1 mm to ~10 mm
2.
Percent of each Wentworth size class:
clay: 0
% silt:
0
% sand:
~10
% gravel: 90
%
3.
Grain sorting (highlight):
poor moderate well
4.
Grain roundness (highlight):
angular subround well rounded 5.
Sediment composition (highlight):
precipitated siliciclastic bioclastic pyroclastic 6.
Describe how and in what environment this sediment might have formed. This group of shells and shell fragments might have accumulated along a beach and high energy environment.
Activity 6.5 B: REFLECT & DISCUSS Imagine that these sediments are rocks. Which of the samples do you think would be the least diagnostic of a specific ancient environment? Why?
Quartz sand would be the least diagnostic of a specific ancient environment, because it is so
common in many different environments.
Activity 6.6:
SEDIMENTARY
ROCKS
WORKSHEET
Sample
number
or letter Does matrix
fizz in acid?
Is matrix made of microscop
ic grains?
Is matrix a mass of
intergrown crystals, or is it clastic?
What is the grain size of
class most particles?
What are the grains composed of? (e.g., calcite, quartz, clay, feldspar, rock fragments, fossils,
ooids, evaporites, pyroclasts) Assign a provisional rock
name
Where might
this sediment
have been deposited/pre
cipitated?
36
No Yes Clastic Gravel sized
grains and fine grains
Silicate minerals and rock fragments.
Breccia Sediments might be deposited in stream gravel, glacial gravel
and beach sand. 37
No No Clastic coarse/ gravel grains Rock fragments, silicate minerals Conglomerate Sediments might be deposited in stream gravel, glacial gravel
and beach sand. 38
No Yes Clastic Sand
Quartz and sand grains
Quartz Sandstone Sediments might be deposited in stream gravel, glacial gravel
and beach sand. 39
No Yes Clastic Sand
Feldspar, quartz Arkose Sediment
Sandstone might be found in sand, beach sand or gravel and sand dunes 40
No Yes Clastic Sand and clay grain sizes
Mixture of sand and clay
Graywacke Sediments may be found in mud
41
No Yes Clastic Pebbles (clay) Quartz, mixture of
clay and silt minerals Shale Typically deposited in slow moving water and found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore from beach sands.
42
No No Chemical precipitate Coarse grained Halite and sylvite crystals Rock Salt/Rock Gypsum
Rock salt is precipitated from sea water and may occur in the Earth as extensive salt
beds. Rock salt deposits from dry lake
beds, inland marginal seas, and enclosed bays and estuaries in arid regions of the world.
43
Yes No Organic / Sand Sand sized white Oolitic Deposited
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Bioclastic spheroids cemented with calcite limestone
from the shells of tiny sea creatures called oolites. It is most commonly found in marine environments
, such as those in the tropical oceans and on coastal plains
.
44
Yes No Organic / Bioclastic Gravel Calcite; composed
of weakly cemented mixture of shells and shell fragments Coquina Deep marine 45
Yes No Clastic (bioclastic)
Sand; many of the fossils are small-gravel
size
Calcite with some shell and skeletal fragments; abundant marine fossils made of carbonate
Fossiliferous Limestone
Might have been deposited on the seafloor
46
Yes Yes Bioclastic Fine grained
Clay class Calcite; mostly clay that breaks into blocks Microcrystalline
Limestone
(micrite)
Precipitated from seawater 47
Yes Yes Organic / Bioclastic Silt grained Calcite; earthy rock composed of microscopic shells
Chalk Sediments might be found in a calcareous ooze
48
No Yes Clastic No visible grains Composed of decay plant material Peat Sediments might be found in a peat bog
49 A
No No Organic / Bioclastic No visible grains 85% Carbon; medium hard; Bituminous coal
Sediments might be
leaves black smudge on fingers
deposited in Ovoid shoals, reefs, Lagoons, shell sand, and peat bog.
49 B
No No Organic / Bioclastic No visible grains 95% Carbon; hard; smooth texture Anthracite coal
Sediments might be deposited in Ovoid shoals, reefs, Lagoons, shell sand, and peat bog.
Activity 6.7 A:
Analyze the images in Fig. A6.7.1, which are from the South Rim of the Grand Canyon near Grand Canyon Village. The edge of the canyon here is formed by a fossiliferous limestone composed of sand-sized clastic grains, called the Kaibab Limestone, deposited about 270 million years ago during the Permian Period.
1.
Notice that some of the beds in the outcrop are cross-bedded. Draw an arrow on the picture to show the direction that the water moved here to make this cross bedding. Refer to Fig. 6.26 as needed.
2.
Does this cross bedding indicate a steady flow of air or water, or does it indicate an oscillating (back and forth) flow? (Fig.6.26) This cross bedding indicates a steady flow of air and water. Activity 6.7 B: REFLECT & DISCUSS Describe your ideas about what the environment might have been like here about 270 million years ago (e.g., Figs. 6.27 and 6.28) and the evidence and logic that you used to reach your conclusion.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
About 279 million years ago the environment might have been surrounded with the flowing
waters. I came to this conclusion based on the evidence that in order to get cross bedding the water needs to be present and flowing. Activity 6.8 A: Analyze photographs X and Y in Fig. A6.8.1.
1.
How are the modern environment (Photograph X) and Triassic rock (Photograph Y) the same? The modern environment and Triassic rock are the same in a way that both have cracks, and clay or mud with footprints in both photographs. 2.
How are the modern environment (Photograph X) and Triassic rock (Photograph Y) different? The modern environment and Triassic rock are different in a way that Triassic cracks have a little depth than the modern ones. In addition, both photographs have
different footprints indicating different creatures existed in different time periods.
3.
Describe the environment in which Coelophysis lived about 215 million years ago in what is now Pennsylvania. The environment in which Coelophysis lived 215 million years ago was a muddy environment. Activity 6.8 B: REFLECT & DISCUSS Use what you learned about sediment and sedimentary rocks. Develop a hypothesis about how the dinosaur footprint in Photograph Y was preserved.
The dinosaur’s footprint may have been preserved till this day because the sediment that it was made in has hardened over time. Activity 6.9 A: Analyze photograph X and Y in Fig.A6.9.1 of a Kansas rock and the modern-day
seafloor near Cape Cod, respectively.
1. How are the modern environment (Photograph Y) and Kansas rock (Photograph X) the same? The modern environment and Kansas rock are the same in a way that both have star shells in them and the shells are preserved in the sand. 2. How are the modern environment (Photograph Y) and Kansas rock (Photograph X) different? The modern environment and Kansas rock are different in a way that Kansas rock has more shell fragments of different kinds. 3. Today, this part of Kansas is rolling hills and farm fields. Describe the environment in which the sediment in this rock sample (Photograph X) was deposited there about 290 million years ago. The sediment in Photograph X was deposited in the oceanic environment that has larger sediment grains. Activity 6.9 B: REFLECT & DISCUSS What would have to happen to the sediment in Photograph X to turn it into sedimentary rock? In order for sediment in Photograph X to turn into sedimentary rock the sediment needs to be compacted or cemented together.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help