Book Cliffs Exercises

The Identification of parasequences Clastic sediments in Outcrop
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The exercises below involve the analysis of parasequence from outcrops. The parasequences are separated from each other using subdividing major surfaces that include TS (transgressive surfaces), mfs (maximum flooding surface), and SB (sequence boundary). The initial exercise is followed by the examination of the stacking patterns of the parasequences.
It is intended that an analysis of parasequences should the lead to the interpretation of the depositional settings of the lithologies that are enveloped by the surfaces listed above. Finally the parasequence sets can be used to identify potential acquifers, acquicludes, hydrocarbon source rocks, reservoirs and seals.

EXERCISES 1-4 
Exercise 1 - Introduction to clastic parasequence identification in outcrop Click on thumb nails to expand images. The objective of this exercise is to learn to identify a vertical set of parasequences within a measured section that was previously described by Van Wagoner et al, (1999). For this exercise you should use the Exercise #1 diagram (see below for exercise, solution and location) the block diagram of a clastic shoreline (Figure 5), and the link between the vertical association of sedimentary structures, depositional systems put together by Coe et al, 2003 (Figure 6), and Table 1 below.

Figure 5. Beach Barrier System
Figure 6. Bookcliffs high frequency clastic parasequence sets (after Coe et al, 2003)


Table 1. The relationship of the sediments of the Blackhawk Formation to depositional setting, tide, waves, and sedimentary structures. (See Figure 6 above).
Setting
Relationship to Waves & Tide
Tidal zone, subject to storm wash-over
Trough-cross bedded fill of tidal inlet, estuarine & fluvial channels
Rooted seat earths & coals
(b) Foreshore & upper shoreface
Zone of breaking waves & the wave swash zone
Trough-cross stratified sandstone sometimes overlain by planar-cross bedded sandstone
(c) Lower shoreface & delta-front sandstones
Just above fair-weather wave base
Current ripple beds
Wave ripple beds,
Hummocky cross-beds
Contorted beds
(d) Transition between offshore shelf & lower shore-face
Between storm wave-base & fair-weather wave-base
Alternations of hummocky cross-stratified sandstone
Highly burrowed silty mudstones
(e) Offshore shelf
Below storm wave-base
Highly burrowed mudstones

The interpretation process is divided into two steps:

First examine the block diagram of Figure 5 and the photographs of Figure 6 that matches hierarchies of sedimentary structures and depositional setting. Also check the four examples that Van Wagoner et al (1990) provided for coarsening upward parasequences for a beach; delta; stacked beaches ; and fining upward stacked tidal flats in the terminology section. Use these associations to subdivide the sediments of measured section into their depositional settings. Now use a combination of this subdivision, and abrupt changes in grain size and/or sedimentary structures to identify parasequence boundaries. The top of the section is a parasequences boundary.
Your next task is to identify marine flooding surfaces in the section provided in the Exercise. The reason for doing this is that these are used to separate parasequences from each other. The marine flooding surfaces or their correlative surfaces are used as a means to separate packages of relatively conformable successions of genetically related beds or bedsets. These are known as parasequences (Van Wagoner et al, 1999). As they point out a marine flooding surface separates younger from older strata. This boundary often has evidence of an abrupt increase in water depth. This may be accompanied by minor submarine erosion or nondeposition, and a minor hiatus is often indicated.
If you intend to apply the techniques you have learnt in this exercise to other successions you should realize that the marine flooding surface often forms the maximum flooding surface (mfs), which marks the boundary between the prograding Highstand System Tract and the top of the transgressive System Tract. The mfs is also often characterized by the presence of radioactive and often organic rich shales, glauconite, hardgrounds and burrows, and widespread thin-bedded concentrations of fauna (condensed sections) with high abundance and diversity. An mfs can often be the only portion of a sedimentary cycle which is rich in fauna. Often in a landward direction the maximum flooding surface may match the underlying trangressive surface formed during or just after the inital transgressive phase that immediately follow sea level lowstands. In this case glossifungites burrows may occur within this surface and the surface may be cemented by carbonates.
In the case of this exercise each of these particular parasequences is a shoaling upward cycle that is bounded by a maximum flooding surface. As a result the lower surface of the parasequences cycle will be the base of the deeper lithofacies layer which overlies the top of a shallowing upward cycle. The upper boundary is the top of a shallower lithofacies layer that is overlain by a deeper lithofacies layer. You can mark each cycle with a triangle that narrows in the direction of the finer grain size. Alternatively you can use a curved arrow to indicate the grain size variation and so it's shoaling upward character. An arrow that moves to the left indicates that the grain size is coarser and so the water is becoming shallower. Patterns of the stacking of parasequence sets are used in conjunction with bounding surfaces and their position within a sequence to define system tracts (Van Wagoner et al., 1988). Note the solution this exercise use the triangle to track variations in the grain size of each parasequence and the maximum flooding surface (mfs) is assumed to lie at this boundary marked by the sharp change in grain size (Exercise #1 Solution).

Exercise # 1 - Kennilworth Section to the North East of Helper in the Book Cliffs:
Approximate Location
Lithofacies
Solution

If you are confused in this exercise you should work you way through the descriptions in the Introduction to high frequency clastic parasequences.

Exercise 2 - Correlate measured sections on the basis of lithofacies and parasequences

Exercise 2 - The objective of this exercise is to continue learning how to identify vertical sets of parasequences in clastic sections while extending this to use these parasequences to correlate the three measured sections located in the Book Cliffs (Exercise #2 diagram linked below).

As in the exercise above the sections provided in this exercise were previously described by Van Wagoner et al, (1999). For this exercise you should combine the interpretation of the Exercise #2 diagram what you did with the Exercise #1 diagram, the block diagram of a clastic shoreline (Figure 5 ), the photographs of Coeet al, 2003 (Figure 6 ) and Table 1. As in Exercise #1 the interpretation process begins with the two steps of Exercise #1 and now includes a third step which involves the correlation of the parasequences you have identified in the three measured sections:

As before examine the block diagram (Figure 5 ) see how hierarchies of sedimentary structures match depositional setting. Use these associations to subdivide the sediments of the three measured sections into their depositional settings. Now use a combination of this subdivision, and abrupt changes in grain size and/or sedimentary structures to identify parasequence boundaries in the sections.

Now identify marine flooding surfaces in the three sections and use these to separate parasequence from each other. Mark each of the parasequences either with triangles that broaden in the directions of coaser grain size or arrows so an arrow that moves to the left indicates that the grain size is coarser and so the water is becoming shallower. As in Exercise #1 each of the parasequences in the three sections is a shoaling upward cycle bounded by a marine flooding surface. Thus the lower surface of each of the parasequences cycle is the base of the deeper lithofacies layer that overlies the top of a shallowing upward cycle. The upper boundary is the top of a shallower lithofacies layer that is overlain by a deeper lithofacies layer. You should mark each cycle with a curved arrow to indicates the grain size variation and so its shoaling upward character. An arrow that moves to the left indicates that the grain ize is coarser and so the water is becoming shallower. Patterns of the stacking of parasequence sets are used in conjunction with bounding surfaces and their position within a sequence to define system tracts (Van Wagoner et al., 1988).

Two bounding surfaces are provided as a framework on which to base the correlation three measured sections of Exercise #2. Correlate the parasequences and make a regional sequence stratigraphic interpretation of facies geometries between the surfaces you have identified, establishing the lithofacies, and the high-frequency sequence stacking pattern and truncation within the section.

Exercise # 2 - Tie sections from Panther Canyon, Kennilworth and Coal Canyon in the Book Cliffs:
Approximate Location
Lithofacies
Solution
 
You will find that correlation of the shales is the key to understanding the depositional geometries of each of the parasequences (see the solution). The question you should ask yourself is: "Are these parasequences aggrading, prograding or retrograding?" To answer this question you should refer to the section in the terminology to determine what the requisite geometries are for each of these processes.
 
Exercise 3 - Regional sequence stratigraphic interpretation
 Exercise 3 - The objective of this exercise is to continue learning how to identify vertical sets of parasequences in clastic sections while extending this to use these parasequences to correlate the twelve measured sections in the Book Cliffs.
As in the two earlier exercises associated with outcrops the sections provided in this exercise were previously described by Van Wagoner et al, (1999). For this exercise you should combine the interpretation of the Exercise #3 diagram with what you did with the Exercise #2 and #1 diagram and the block diagram of a clastic shoreline Figure5. There is now a difference. Previously all the parasequences of the three sections built out over each other. Now you should find evidence of updip erosion to the West. You should ask yourself "What is the evidence of this erosion and what is initiating it?"Again use Figure 5 to help your interpretation.
As in Exercise #1 and Exercise #2 the interpretation process begins with the two steps of Exercise #1 and the third step of the correlation of the parasequences you have identified in the twelve measured sections. As before examine the block diagram (Figure 5 ) that matches hierarchies of sedimentary structures and depositional setting. Use these associations to subdivide the sediments of the twelve measured sections into their depositional settings. Now use a combination of this subdivision, and abrupt changes in grain size and/or sedimentary structures to identify parasequence boundaries in the sections. As before identify marine flooding surfaces in the sections and use these to separate parasequences from each other. Look for evidence of updip and westward erosion.
As in Exercise #1 each of parasequences in the lower portions of the sections is shoaling upward cycle bounded by a marine flooding surfaces. Thus the lower surface of each of the parasequences cycle is the base of the deeper lithofacies layer that overlies the top of a shallowing upward cycle. The upper boundary is the top of a shallower lithofacies layer that is overlain by a deeper lithofacies layer. As before you should mark each cycle with either a triangle or a curved arrow to indicate the grain size variation and so its shoaling upward character. In the sections to the east the arrow that moves to the left indicates that the grain size is coarser and so the water is becoming shallower (ask the question are these a shoreline represented by a beach, stacked beachs, a delta or tidal flat). However in the upper portions of the nine sections to west the arrow that moves to the right and indicates that the grain size is finer. In this case the water is still becoming shallower but the reduced grain size reflects a setting (either tidal flat, estuarine channels, or fluvial over bank) protected from the winnowing effects of waves. As before the patterns of the stacking of parasequence sets are used in conjunction with bounding surfaces and their position within a sequence to define system tracts(Van Wagoner et al., 1988).
Two bounding surfaces are provided as a framework on which to base the correlation twelve measured sections of Exercise #2. Correlate the parasequences and make a regional sequence stratigraphic interpretation of facies geometries between the surfaces you have identified, establishing the lithofacies, and the high-frequency sequence stacking pattern and truncation within the section. You will find that correlation of the shales is the key to understanding the depositional geometries of each of the parasequences. Note the updip westward erosion of the upper parts of the sections.

Exercise # 3 - Tie sections from Gilson Gulch to coal Canyon in the Book Cliffs:
Approximate Location
Lithofacies
Solution
 
As in Exercise #2 the question you should ask yourself is: "Are these parasequences aggrading, prograding or retrograding?" To answer this question you should refer to the section in the terminology to determine what the requisite geometries are for each of these processes.
For more detailed discussion of high frequency sequence analysis of the Book Cliff escarpment on which this exercise is based examine the references at the base of the Introduction to high frequency clastic parasequences in outcrop.
Exercise 4 -“Waltherian” Facies Shifts (by Dr. Jennifer Aschoff)
Exercise 4-The objective of this exercise is to continue learning how to identify vertical sets of parasequences in clastic sections (again from measured sections in the Book Cliffs) while extending this to use of parasequences and Walther's Law to determine the depositional setting of a series of shoreline facies and to determine “non-Waltherian”, vertical shifts in facies, i.e. those facies that are adjacent to each other in the vertical section but were not be adjacent to each other in the depositional setting! Download the pdf file of this exercise and its text by clicking on the thumbnail image below.
 
Walther's Law - a first exercise in understanding
Approximate Location
Sections
Table
 
“Waltherian” Facies Shifts:
A Basic Exercise in Outcrop-based sequence stratigraphy
Note: Stratigraphic Data and Maps are From VanWagoner, 1992
This exercise was designed by Dr. Jen Aschoff as a basic exercise in sequence stratigraphy for
Undergraduate Petroleum Engineering Students at Colorado School of Mines
 
Facies interpretations have been simplified.
 
Learning Objectives:
  • 1. Walther’s Law
  • 2. Facies interpretation
  • 3. Basic sequence-stratigraphic correlation using outcrop data
 
1. For the 3 stratigraphic columns and facies descriptions provided above (Sections and Table):
 
a) Interpret the depositional environments for each facies in the 3 stratigraphic columns
provided (Figures 1). For your answer, fill in the “Depositional Environment Interpretation”
column of Table 1. This question may require you to research each environment in your
book, or at the library. Cite your sources!
 
Choose from the following depositional settings:
    • Offshore Marine
    • Lower Shoreface
    • Upper Shoreface
    • Tide-dominated Estuary
    • Braided Fluvial (thick-bedded)
    • Meandering Fluvial (thin-bedded)
    • Floodplain
b) List the evidence that supports your interpretation. For your answer, fill in the “Evidence”
column of Table 1
 
c) Pick the “non-Waltherian”, vertical shifts in facies. That is, facies that are adjacent to each
other in the vertical stratigraphy but would not be adjacent to each other in the modern mapview.
Hint:
“NON-Waltherian” Examples (don’t follow Walther’s Law)
Ex1: offshore marine deposits overlain by fluvial
Ex2: fluvial deposits overlain by offshore marine
Waltherian Examples (DO follow Walther’s Law)
Ex1: floodplain deposits overlain by fluvial channel deposits
Ex2: offshore marine deposits overlain by lower shoreface deposits
 
d) Distinguish the basinward from the landward shifts.
“basinward shift” (or, sequence boundary): overlying facies record a more proximal
environment (such as alluvial fan, fluvial) than the underlying faices.
“landward shift” (or, flooding surface): overlying facies record a more distal environment
(such as offshore marine, or lower shoreface) than the underlying facies.
 
e) Draw lines that correlate (connect) similar non-Waltherian shifts (i.e., connect the basinward
shifts with other basinward shifts, and landward shifts with landward shifts).
 
2. Describe and illustrate the evolution of the landscape through time as recorded by these strata.
Do this by picking time-lines for each of the stratigraphic columns and drawing a
paleogeographic map for each time-line using the map provided above (Approximate Location).
 
Wednesday, April 20, 2016
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