Figure 2 is a simplified geological cross-section of a well-studied area, and the geologist who studied the area also wrote brief descriptions of the rock units (designated by letters A, B, C, D, E, F, G, K and X):
(A) limestone containing well-preserved fossil ammonites cemented by a fine-grained carbonate mud.
(B) sandstone with red-coloured grains (with a grain-size histogram similar to Book 6, Figure 4.
7a (ii)); rounded pebbles of sandstones and limestones are present at the base of the bed; lacks any fossils.
(C) coal bed containing woody plant fossils of upper Carboniferous age.
(D) pure quartz sandstone (with a grain-size histogram similar to Book 6, Figure 4.
7a (iii)); contains abundant burrows (trace fossils).
pressure/ 108 Pa
(E) limestone containing well-preserved corals (similar to most modern corals) and brachiopods (often with both valves joined and intact) cemented by a fine-grained carbonate mud.
(F) mudstone containing trilobites; the base of mudstone is defined by an irregular contact with strongly folded underlying rocks.
(G) strongly folded schists made predominantly of mica, quartz and garnet.
(K) coarse-grained granite intruding highly folded and deformed metamorphic rocks (G).
(X) cross-cutting basaltic dyke which has been radiometrically dated at 69 ± 3 Ma.
Figure 2 A simplified geological cross-section through the upper 1000 m of the Earth's crust of a well-studied area.
(a) Using Figure 2 and the brief descriptions provided above, describe the most likely environments of formation for each of the sedimentary rocks A–F.
Give the evidence from the descriptions to support your answer.
(Guideline: up to 250 words in total.
(b) Figure 2 contains two major boundaries: (i) an unconformity and (ii) a fault.
Describe the locations of each of these two features on Figure 2, and the geological evidence you used to identify them.
As part of your description of the fault, state whether it is formed by tension or compression.
Describe the relative motion either side of the fault, including the direction and relative movement of the adjacent rock units.
(Guideline: three or four sentences for each feature.
(c) Using the information provided in Figure 2 and in the geologist's descriptions, complete this copy of Table 2 to show a brief summary of
Tutor-marked assignment TMA06
the geological history of the area in the correct order from oldest at the bottom to youngest at the top.
(Note that the oldest and youngest events have been completed and will guide you to the level of detail to be included in your answer.
(Insert your completed copy of Table 2 into your assignment document.
Table 2 Summary of the geological history represented by Figure 2.
(d) In the laboratory small zircon crystals were separated from granite (rock K).
Isotopic analysis of these zircon crystals gives a 207Pbratio of 0.
Using Figure 3 (an enlargement of the dashed blue line at bottom left of Figure 6.
11, Book 6, page 211) and the half-life of 235U (7.
04 × 108 years), estimate the age of the granite in Ma to two significant figures.
(Show all your working.
Erosion of the rocks to form the present land surface
Deposition and burial of mud sediments to form mudstones
012 number of half-lives, n
Figure 3 A plot of the variation of the daughter/parent (D/P) ratio against the number of half-lives elapsed (n).
(e) Referring to all of the available evidence (i.
the radiometric ages of the igneous units, the descriptions of each rock unit, your sequence of geological events in your answer to part (c), and the association of fossils with particular geological time periods that you learned about in Book 6), determine the most probable geological period(s) and associated era(s) in which each of the sedimentary rocks A–F were deposited.
(Guideline: up to 200 words in total.
From the attachment please extract only question 3.
In a) i do not need names of the rocks but environments they formed and evidence to support it! I DO NEED ALL POINTS OF QUESTION 3 TO BE ANSWERED.
I had a rather bad experience with this question so far.
If you really think you can do it then name your price and I will be happy to pay if I get a nicely done answer.
Thank you very much