I have fallen behind in my coursework and need help completing a Geology assignment (see attached). All course notes will be provided.
Question 1 (28 marks)
Design and construct one table that succinctly lists eight distinct sequence
stratigraphical features or sedimentary features that are relevant to sea-level change
and sediment supply. Put these features in the rows of the table. In the columns
indicate whether or not these features occur in each of the following settings:
1. a carbonate ramp,
2. a siliciclastic system with a shelf break,
3. a mixed siliciclastic/carbonate succession in a carbonate rimmed shelf
setting.
For at least six rows, describe features that show how one of the settings differs from
the other two. Briefly comment in the table cells on all features that do not apply to
that particular setting. Assume that all the successions are deposited in a constantly
subsiding basin in the tropics under icehouse conditions and that there is no change
in the climatic conditions or the tectonic setting. (A table)
Learning outcomes: In your answer to Question 1 we are looking for demonstration
of: knowledge and understanding of the sedimentary system in these different
settings (Kn1), the ability to synthesise information from figures and text in the
module materials (C3), good communication skills in the way that you set out the
information in your table and keep it succinct (Ky2), use of appropriate terms and
application of the theory to summarise the features in these different settings and
conditions (C1).
Question 2 (68 marks)
This question requires you to interpret the sequence stratigraphy of the succession
shown in Figure 1 (shown at the end of the question) which was deposited close to
the shoreline over several million years. The question is structured to help you to
progressively build up your interpretation in a manner similar to that followed in
previous examples such as Study session 22.8 on Hundale Point. Broadly this is:
1. Examine the graphic log and other evidence and build up a picture of
the deposits, the processes that acted and the depositional
environments.
2. Look for parasequences and their stacking patterns (but remember
they are not always present).
3. Put all of this evidence together to complete a sequence stratigraphical
analysis.
Using the information provided in Figure 1 and the facies description presented at
the end of the question, prepare each of the items (a) to (g). You are advised to read
each part of the question carefully and to note that some parts of the question refer
you to specific beds in Figure 1.
a. (8 marks) Draw a 3-D block diagram, showing how these three main
facies associations: marine, lagoonal and alluvial might relate to each
other laterally (for an example of the style see Figure 3.8, p. 49 or
Figure 4.10b, p.71 in Coe et al. (2003)). The facies should be labelled.
The longitudinal vertical face of the block diagram should show
progradation of these facies over time. (A sketch 3-D block diagram)
b. (8 marks) Draw a sketch graphic log showing the expected shallowingupward succession of all the individual marine and lagoonal facies,
assuming all the facies obey Walther’s Law. If there is a variation in
the sedimentary structures that is likely to relate to water-depth you
should show these sedimentary structures in the appropriate order so
that they fit with the overall shallowing upward. You do not need to
include facies M6a. You should use the same symbols as those in
Figure 1 and clearly label each of the facies, you do not need to
reproduce the key for Figure 1. The thicknesses do not matter in this
case. (A sketch graphic log)
c. (8 marks) Assuming a fairly constant sedimentation rate for beds 6a to
8 in Figure 1, state what this part of the succession indicates about
relative sea-level change. Based on your 3-D block diagram for (a),
draw a second 3-D block diagram to show how the environment might
have changed to deposit beds 7 and 8. In the longitudinal vertical face
of the block model, you should show both the information you had in
part (a) and, on top of that in simplified form the information that you
have about the change indicated by beds 7 and 8, so that it is clear
how the facies pattern has evolved over time. The facies should be
labelled. (Advisory limit: 60 words and a sketch 3-D block diagram.)
d. (4 marks) Beds 10 to 13b show interbedding of facies L3 and L4. Each
pair of L3 and L4 beds can be interpreted as a parasequence. In the
form of a bulleted list complete the following:
for the parasequences in beds 10 to 13b, describe the
overall trends in the proportion of facies and thickness of
the parasequences
state whether beds 10 to 13b show overall shallowing or
deepening
identify the parasequence stacking pattern. (Advisory
limit for (d): 100 words)
e. (8 marks) The facies in beds 14a to 16 in Figure 1 show a number of
parasequences that demonstrate a progradational stacking pattern.
Each flooding surface is overlain by a pebble bed (facies M6a). Draw
a sketch proximal to distal cross section of this stack of
parasequences showing facies M4, M6a and M5. Clearly indicate the
position of the log of beds 14a to 16 on the cross section with a
vertical line. The cross section should be in the style of those shown
in the parasequence animations in Study session 22.3 or Figure 4.7 of
Coe et al. (2003). The sketch does not need to be exactly to scale but
should clearly show the relative proportions of the different facies and
parasequences. (Sketch cross section)
f. (24 marks) Prepare a sequence stratigraphical interpretation of the
whole succession and present this as an annotated version of Figure
1. Succinctly justify each part of your sequence stratigraphical
interpretation by compiling a bulleted list of accompanying notes that
are cross-referenced to your annotated Figure 1. Use the bed
numbers to identify the different parts of the log (e.g. ‘Bed boundary
15/16 is interpreted as a ….because…’; ‘Beds 9 and 10 show….and
are interpreted as…’). The bulleted list should start with the oldest bed
and/or contact and be in stratigraphic order. You should use the
information in parts (a) to (e) to help with your interpretation and cross
reference these where appropriate. (An annotated Figure 1 clearly
showing your sequence stratigraphical interpretation and a bulleted
list of cross-referenced explanatory points with an advisory limit of 600
words.)
Hints: Not all parts of the succession contain parasequences; bed 5 is
very condensed; look for all the erosion surfaces, but remember that
not all erosion surfaces necessarily relate to relative sea-level fall; use
your answers to parts (a) to (e): they should help you with your
interpretation. Beds 3 to 5 are probably the most difficult part to
interpret and there may be more than one interpretation from the data
available, bed 8 is a good place to start, working up and then
returning to bed 3 and completing up to bed 8. You may find it helpful
to colour-code the facies on one copy of Figure 1 and then do your
sequences stratigraphical interpretation on a new copy. If you colourcode the facies this does not need to be submitted with the TMA.
Remember that you need to interpret the whole succession in a
consistent fashion and that there are likely to be similar patterns.
g. (8 marks) Prepare a succinct concluding summary describing the key
points about this sedimentary succession, the environments of
deposition and sequence stratigraphical interpretation. Your summary
should include any overall trends shown by the succession as a whole
and a prediction of any deposits that are likely to be found in a more
distal locations. (Advisory limit: 300 words)
Learning outcomes: In your answer to Question 2 you will need to apply your
understanding of sedimentary rock successions and sequence stratigraphy
methodology to an unfamiliar succession (C1). To do this will require you to use and
synthesise information from Figure 1 and the description of facies to make an
informed interpretation (C3). Parts (a), (b), (c) and (e) require you to present your
interpretation in the form of figures which will enable you to demonstrate your skills in
summarising information in the form of graphics (Ky3). You should use your
communication skills to present clear and succinct answers in both graphical and
written form (Ky2).
Figure 1. The oldest deposits are in the bottom left. The top of the left-hand column
joins on to the base of the second column, and so on, as shown by the diagonal
lines. Please see notes below for further information on each of the facies (M2, M3,
M4, M6a, A1, L3, L4). Note that flaser and lenticular bedding is often associated with
tidal deposition. Tabular cross-stratification is an alternative name for planar crossstratification. The horizontal and low angle lamination are variations on planar
stratification.
Accompanying notes: Facies description for use in
conjunction with Figure 1
Marine facies association
Facies M2: Highly bioturbated, glauconitic, sandy mudstones. Diverse micro- and
macro-invertebrate faunas. Any primary sedimentary structures have been destroyed
through intense bioturbation. The amount of clay compared to other facies in the
succession and the type of fauna indicates that this is likely to have been deposited
well below fairweather-wave base. Glauconite indicates this bed is condensed and
reworking of the sediment over a long time period has given rise to a higher than
expected average grain size.
Facies M4: Fine-grained, well-sorted sandstone with horizontal lamination and lowangle lamination (planar stratification). Decimetre-scale cross stratification and waveformed ripples in some horizons. The grain size, trace fossils (Ophiomorpha) and
sedimentary structures suggest deposition in the shoreface and foreshore zones.
Facies M5: Fine-grained sandstone with large-scale cross stratification. The surface
of the sand grains is frosted. The gradational boundary with facies M4 suggests that
this facies was deposited above high water mark as aeolian dunes.
Facies M6a: Pebble beds associated with reworking during flooding.
Lagoonal facies association
Facies L3: Weakly bioturbated, rippled, flaser- and lenticular-bedded fine-grained
sandstones and silty claystones. Fossils include leaves and wood. Invertebrate
fauna indicates brackish water. This facies is interpreted to represent lagoonal facies
behind a barrier that is protected from open-marine conditions.
Facies L4: Interbedded coals and palaeosoils. The association and gradational
contact with facies L3 suggests deposition behind a barrier protected from openmarine conditions.
Alluvial facies association
Facies A1: Coarse- to medium-grained sandstones with sub-ordinate amounts of
fine-grained sandstone, mudstones and conglomerates, encased in mudstones.
Decimetre-scale, trough- and tabular cross-stratification are the principal
sedimentary structures in the sandstone bodies. The sandstone bodies form thick,
erosively-based and fining-upward successions that are 3 to 15 m thick. The
sandstone bodies contain mud-filled abandonment channels. Each fining-upward
sandstone body succession is interpreted to be the result of sedimentation on the
point bar of a meandering river.
Estuarine facies
Facies E4b: Bi-directional, cross-stratified and lenticular bedded fine- to mediumgrained sandstones interbedded on a fine scale with dark-grey, carbonaceous, silty
clay. This facies is interpreted as the sedimentary infill of a tidal channel.