it’s a geology lab assignment having three parts. Please Ignore part 3 just do parts 1 and 2 .
WEEK 4
– 3040 Notes on FACIES & ENVIRONMENTS
Reading: http://www.seddepseq.co.uk/SEQ_STRAT/WALTHER.htm
FACIES (Latin meaning face, look, appearance) = important internal characteristics,
properties
A way to divide and group rocks
Informal and adaptable (can use at all kinds of scales, tailor it to your needs)
Uses of Facies (here using examples that may all refer to the same set of rocks)
1. Descriptive/objective (factual) – our preferred usage e.g., graded ss facies
2. Process/genetic e.g, turbidite facies (implying process of density driven turbidity
currents)
3. Environmental e.g., deep sea fan facies (environment such rocks may form in)
Facies patterns – designed to depict important features of the rocks, standard patterns and colors,
but it’s always a good idea to have a legend!
Facies Models (often expressed as 3-D block diagrams), show facies relationships, associations
to help interpretations
*** Walther’s Law: laterally adjacent facies can be vertically imposed /stacked, assuming no
major break- unconformity or fault, etc.
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Transgression – shoreline moves landward (retrogradational stacking)
Regression – shoreline moves seaward (progradational stacking)
Facies Rules, Facies Models and relationships
STRATIGRAPHIC SECTIONS – watch short 5 min. video
1) Title at the top, centered, all capital letters.
Ex:
STRATIGRAPHIC SECTION OF THE CRETACEOUS BLACKHAWK
FORMATION NEAR HELPER, UT
2) Time divisions and scale along the far left side of the column shows
series, stage, formation and meters (or feet) above base.
3) Label the lithologic column “Grain size” or “Weathering profile” (standard
has been 1” = most resistant, ½” = least resistant, but sometimes we
exaggerate that to fit more in, and/or if we will need to reduce the column for
publication, etc.). Some columns use tick marks for the different grain size
divisions.
4) Use standard lithologic symbols. If you have several units, color the
beds to match your map units.
5) Use standard symbols to represent scoured (erosional surfaces,
unconformities), faults or sedimentary structures, keyed to a legend.
4) Include where samples, data, fossils or photographs were collected.
5) Give brief lithologic descriptions (in a consistent ordered format):
Letter neatly or use computer graphics for the lithologic descriptions.
Each description must be across from the beds it is describing.
Align all descriptions (left-justify).
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Phrases or common abbreviations are O.K.! You do not need completed
sentences.
6) Include “Drawn by” and the date in the bottom right corner or on the top
right below the title.
-See Template examples
Here’s an example from Dinosaur National Monument below. The
descriptions are short because this is only exhibiting the basic formations.
Sometimes what you include is a function of your purpose. Some sections
can be very details where the measurements included each bed, even at cm
scales! Some sections are very generalized. If you can’t fit all the words or
descriptions in, you can also list basics, with an extra appendix of the full
details
Choose appropriate scale so that the entire section can be represented at an
appropriate level of detail (in a paper world, this means multiple pages or a
fold out, but could be a lot of scrolling or nested details in a digital format).
.
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DEPOSITIONAL ENVIRONMENTS
Watch this 14 min. video as an overiew (though admittedly the video imagery can be tough
if you get carsick!)
DEPOSITIONAL ENVIRONMENTS
Sedimentary realms or envts distinguished by parameters:
•
physical (velocity, direction, wind, waves, climate. T, tectonics, etc.)
•
chem (comp of water, geochem of rx, provenance)
•
bio (flora, fauna, affects of animals, reefs, etc.)
CONTINENTAL
Glacial
Eolian/desert
Alluvial
Fluvial
Lacustrine
Swamp
Cave (Spelean)
TRANSITIONAL
Deltaic
Estuarine – Lagoon
Tidal
MARINE Barrier Isl. – Strand Plain
Beach – Shoreline
Shelf (Neritic)
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Slope (Bathyal)
Deep – Sea Fan
Basin
Abyssal
___________
GLACIAL
Ice as geol agent
Combo of : Low T, high rates of ppt with extremely low rates of evap
Processes:
1. Glacial flow :
2. Glacial Erosion (striations):
3. Glacial Transport:
4. Glacial Deposits (Till)
glacial-marine drift
Recognition:
1. types of glacial depos (10s m thick)
2. landforms
3. gradation of glacial sheet to glacio-fluv outwash plain
Reading
http://geowiki.ucdavis.edu/Wikitexts/UCD_GEL_109/Alluvial_Fans/Glacial_Environments
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LACUSTRINE / LAKES
A. Formed by: tectonic subsidence, faulting, glacial erosion
B. Waters: water chem., water temp.
vary widely in character, with variable degrees of permanence, salinity (fresh, brackish,
saline, hypersaline), alkalinity etc.
C. Sed supply
D. Climate
E. Facies (ideal – concentric patterns from shoreline to basin center)
G. Recognition
H. Economics – oil shale, evaporite minerals, some coals
o
o
o
o
o
o
o
Need subsidence: usually tectonic
Others formed by damming (glacial, volcanic, mass wasting, etc.)
Not that common in the geologic record
Strongly affected by climate
Hard to differentiate from marine at times
25 largest today: 10 glacial dam, 7 cratonic depressions, 4 rift valley (Baikal, E Africa)
Good oil source
– Found: faulted grabens or other subsiding basins, internal drainage & limited outflow.
– Sensitive to changing subsidence and climate patterns. Lake margins, water chemistry, and lake
ecology are variable over short stratigraphic intervals.
– Lake shorelines can move basinward either by progradation or by withdrawal of water.
Withdrawal (lake level fall) leaves only a limited rock record (mainly dessication features).
– Gradual lake ‘filling’ would show upward-coarsening from distal lake environments to
deltaic/fluvial environments. This is only one of several possible vertical successions.
– May find: laminated, kerogen-rich mudstones (good source for oil), turbidite beds, fresh or
saline-water fossils (absence of marine invertebrates), limestones, transition to fluvial-deltaic
facies.
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Other references, Recommended watching:
WATCH Youtube ppt video of Matthew Clapham on Facies
If you want additional help understanding these, you can also try:
Identifying Transgression and Regressions (Jennifer Lewis, 7 mins)
Ref: If you want more reinforcement of these ideas, you can Watch Dawn Sumner’s Youtube
video http://www.youtube.com/watch?v=ZSsULiPouTo
Transgression, Regression
Ref. for more explanations see:
http://www.geologyin.com/2015/09/how-to-identify-transgression-and.html
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Lab 4
GEO 3040
Name:
Sedimentary Structures
Due Date: Sept 23, 2020 (beginning of lab)
Objective: You have focused on texture and classification of sedimentary rocks. Now you will
examine sedimentary structures that provide valuable clues for hydrodynamic conditions and
interpreting depositional environments. Parts 1 & 2 can be completed at home. Part 3 should be
done at field sites.
Materials Needed: Internet access, Calculator/Computer (for calculating ripple index)
Part I – Common Sedimentary Structures
Carefully examine each rock sample and answer the associated questions. You will want to
refer to the recommended Boggs text and lecture notes as well for additional (web, youtube,
etc.) references for identifying and interpreting the samples. From SketchFab –
1. Trough Cross Bedding https://sketchfab.com/3d-models/sedimentary-structures-troughcross-bedding-aaaf6655e6234227a052379773da8aca
A. What characteristics justify the cross-bedding name of this sample?
B. What would be the Froude number/conditions this would have formed under? (And you
should understand why!)
a) Fr >1
b) Fr = 1
c) Fr < 1
2. Ripples https://sketchfab.com/3d-models/ripple-marks-prac-specimen-test7d96d73707e341c4b452044698e1fbbe
A. What kind of ripples are these?
d) Current
e) Wave
f) Interference
g) Adhesion
h) Eolian
B. Cite evidence:
C. Give an approximate estimate of the Ripple Index (R.I.), and make sure this is consistent with
your answer to A. above.
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3. Ripple Marks 3 https://sketchfab.com/3d-models/sedimentary-structures-ripple-marks-32b4357ae52cb498ea0ed8e76c6f23563
A. What kind of ripple marks are these?
a) Current
b) Wave
c) Interference
d) Adhesion
B. Cite evidence:
a) Asymmetrical in cross-sectional view
b) Symmetrical in cross-sectional view
c) Presence of fossils
d) Presence of salt minerals
C. Describe the shape of the ripples at or over the crest, (peaked or rounded) 1 pt
a) Peaked
b) Rounded
D. Describe the shape of the ripples along the crest
a) totally, perfectly straight,
b) slightly curved though relatively straight
c) very curved, linguoid shape
E. In one upper left corner- give a description of what happens to the crest that lends further
support to your interpretation of what type of ripple this is:
4. Raindrop Impressions https://sketchfab.com/3d-models/sedimentary-structures-raindropimpressions-bbdd19454c374c64bf2d41a141d7f3c4
A. Do you see perfect circular impressions?
a) Yes, all are totally, perfectly circular
b) Only a few are truly circular
c) Not a single one is circular
B. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
C. Describe the shape of the ripples in cross section, (symmetrical or asymmetrical)
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5. Synaerisis (??) Cracks
https://sketchfab.com/3d-models/sedimentary-structures-synaerisis-cracksf5a4cd1861a94b128c7841e1c51083dc
A. Give the correct spelling for what this post meant the structure to be: ___________
B. Is this a good interpretation or not? Cite the weakness of this interpretation.
C. What do you think it could be instead and why?
6. Now look at what he has labeled Mud Cracks 2
https://sketchfab.com/3d-models/sedimentary-structures-mud-cracks-2e76afb108e954d37910ed5b79759ec76
A. Choose the correct description for these:
a) Complete, well-formed polygons
b) No connected cracks to form polygons or geometric shapes, cracks with pointed
terminations
c) All rounded cylindrical forms with consistent thickness
B. What do you think a correct name for this structure should be?
_______________________________
7. For reference, compare it to this - Mud Cracks
https://sketchfab.com/3d-models/sedimentary-structures-mud-cracksee77184000164d74b9288879859ed9a0
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. Choose the correct description for these:
a) Mostly complete, well-formed polygons
b) No connected cracks to form polygons or geometric shapes, cracks with pointed
terminations
c) All rounded cylindrical forms with consistent thickness
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Note:
Another model for mud cracks is here: https://sketchfab.com/3d-models/mudcracks-austriaa56dd0c71d934f029bb1cd9d61247485
8. Tool Mark https://sketchfab.com/3d-models/sedimentary-structures-tool-marks-272e6a5b4a346404380441e306d0a7dc4
A. What side is the sole or base of the bed?
a) side with bumps
b) the side with a number (5 digits) written in black
B. What kind of tool marks do you see here?
C. What can be inferred about the paleo current direction or type of flow?
9. Hummocky cross stratification (HCS) https://sketchfab.com/3d-models/hummocky-crossstratification-in-sst-acf1b6efc0154b91aa13f3162176cef5
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. Given that most of these are hand specimens, you can guess that this sample is about 10 cm
across. The scale of true HCS is about 1 m spacings or more of the domal hummocks. You do
see some laminations here that are at an angle, and you could likely slap a protractor up on
your screen to see what these angles are, but give an estimate of the largest dark
orange ”lines”:
a) 0-5 o
b) 5-15 o
c)
20-45 o
d) > 60 o
C. What angles are HCS supposed to be at?
a) 15 o
D. What is the more likely appropriate name for this sedimentary structure?
a) Swaley cross stratification
b) Soft-sediment deformation
c) Trace fossil
d) Ripple cross lamination
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Other SketchFab samples
10. Sed Rocks Sample 2 https://sketchfab.com/3d-models/sedimentary-rock-sample-2403fef2f843f4595aa34a76d95fd4e3d
A. What is the thickness of the bedding?
a) Very thick bed
b) Thick bed
c) Medium bed
d) Thin bed
e) Very thin bed
B. What is the thickness of the laminae?
a) Thick laminae
b) Thin laminae
11. Pebbly Beach convolute bedding
https://sketchfab.com/3d-models/pebbly-beach-convolute-beddingc57ff38facd14d609ed13ecb8a5af93d
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. Another appropriate category name for this structure is:
a) Massive
b) Tool Marks
c) Reverse graded
d) Soft-sediment deformation
12. Flute casts 2, Germany
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. What originally formed this structure “cast”:
a) Migrating ripples
b) Upper flow regime
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c)
d)
e)
Eddy currents scoured along a bed
A tool being dragged by a current
None of the above
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Part II –Regular 2-D photo images
13. Samples UUSS 277 and 068088.17
What sedimentary structure do you observe in both samples? What information do these
samples yield about depositional conditions (flow regime, sedimentation rate, etc)?
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14. Samples UUSS 303 and 06083.13
A. What sedimentary structure do the below samples exhibit? _____________
B. Indicate stratigraphic up. (Write top, left, right, or bottom).
C. From which type of deposit would this likely form?
a) Crevasse splay
b) Alluvial fan flow
c) Turbidite
d) Any of the above
e) None of the above
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15. Field image in fine sandstone below. Hint: Scale card ~ 1 m across, also see diagrams
A. Name the structure: __________
B. What Froude number does this structure form at? _______
a) Fr >1
b) Fr = 1
c) Fr < 1
d) not applicable
C. The flow would be:
a) unidirectional
b) oscillatory/combined
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16. Field image below. Hint: This is a medium-grained sandstone. Scale card ~ 7 cm
A. Name the structure: __________
B. Does this structure form at, above, or below a Froude number of 1? (Write as Fr = 1, Fr > 1,
or Fr < 1.)
C. What bedform comprises this structure? ___________
D. Would the flow be unidirectional or oscillatory?
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17. Float slab at Gentile Wash, near Helper UT
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. Another appropriate category name for this structure is:
a) Massive
b) Tool Marks
c) Reverse graded
d) Soft-sediment deformation
C. More specifically the biggest structures are called:
a) Trace fossils
b) Diagenetic features
c) Groove marks
D. What kind of paleocurrent direction would this give us?
a) Unidirectional (specific direction)
b) Bi- directional (flow could have been either direction along the marks
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18. Oregon coast 1
A. Choose what type of structure this is:
a) Intrabed
b) Bedding plane
c) Trace fossil
d) Diagenetic
B. Another appropriate category name for this structure ( ~ 30 cm across) is:
a) Massive
b) Tool Marks
c) Reverse graded
d) Soft-sediment deformation
C. More specifically it is a:
a) Load or flame structure
b) Fossil
c) Diagenetic feature
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19. Oregon Coast 2
A. Is the type of structure is shown in the 2 pictures (sometimes aligned parallel to bedding) a
bedding, fossil, or diagenetic feature?
B. More specifically, these would be called: ____________.
C. These are defined as: ___________
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20. Mystery: This last one about 1 m across is a combination of physical (temperature changes)
and biochemical processes (possible lichens, salts, other). It is called tafoni or honeycomb (you
can look it up). Sometimes you will see it in sandstones of S. Utah.
A. This would be a structure considered:
a) Primary depositional
b) Secondary, diagenetic, weathering
c) Trace fossil
d) None of the above
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Part III –A Field Trip to check out sandstone!
Your choice, whatever is close to you or what you prefer!
Visit only one of these 3 parks at general areas shown in pictures below.
A. Gilgal Sculpture Garden 749 E 500 S, Salt Lake City, UT 84102 (open 8-8)
B. Marriott Library on campus - SW side red ss wall, accessible parts by S steps
C. Knudsen Park 6293 Holladay Blvd Holladay UT 84121
* Bring your handlens and your packet of comparison sand grain charts & photo scales
Submit 3 photos.
1. You or selfie at the site, proving you were there!
2. “Outcrop scale” context picture with some recognizable scale (e.g., person, walking stick,
etc.)
3. Close up picture of some interesting sedimentary structure (bedding, ripples, etc.) with
your photo scale.
Answer the following questions on your sandstone structure:
1.
Specify these clastic textures of the area at the sed structure you photographed:
Grain size (specific!):
Rounding:
Sorting:
Composition (mineralogy):
2.
Dott classification name:
3.
Has there been any diagenesis since the original deposition?
Explain your answer why/why not.
4.
Identify the sedimentary structure:
5.
Where do you think your rock is from and explain why:
a.
Some local Mesozoic eolian unit
b.
An imported sandstone (from India?)
c.
A local quarried shallow water bedding plane deposit
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