454/01 GEOLOGY GL4 INTERPRETING THE GEOLOGICAL RECORD. P.M. THURSDAY, 17 June (2 Hours)

Transcription

1 Candidate Name Centre Number Candidate Number WELSH JOINT EDUCATION COMMITTEE General Certificate of Education Advanced CYD-BWYLLGOR ADDYSG CYMRU Tystysgrif Addysg Gyffredinol Uwch 454/01 GEOLOGY GL4 INTERPRETING THE GEOLOGICAL RECORD P.M. THURSDAY, 17 June 2004 (2 Hours) Examiner Section A Section B Total ADDITIONAL MATERIALS In addition to this examination paper, you will need: the Geological Map Extract (Stoke-on-Trent); a hand-lens or magnifier to study the map (optional); a calculator. INSTRUCTIONS TO CANDIDATES Answer all the questions. Write your answers in the spaces provided in this booklet. INFORMATION FOR CANDIDATES The number of marks is given in brackets at the end of each sub-question. Candidates are reminded that marking will take into account the quality of communication used in your answers. No certificate will be awarded to a candidate detected in any unfair practice during the examination. TJ*

2 2 Examiner SECTION A Answer all questions in the spaces provided. This Section should take approximately 1 hour to complete. 1. Figure 1 shows diagrams of two sedimentary rocks (A and B), both derived from the same igneous rock source. Note that the diagrams are drawn to different scales. fine-grained matrix quartz original grain outline feldspar (29% by volume) calcite cement 0 mm 1 Scale bars (mm) 0 mm 1 Rock A Rock B Figure 1 Refer to Figure 1. (a) Name a type of igneous rock from which rocks A and B might have been derived. [1]... (b) (i) Describe two differences in texture between rocks A and B. Explain why the textures differ. [4] Description Explanation

3 3 Examiner Account for the difference in shape of the quartz and feldspar grains in Rock A. [2] (iii) Suggest why feldspar is absent from Rock B. [3] (c) Select the most likely environment of deposition for rocks A and B from the list below by completing the relevant box with the appropriate letter (A or B). [2] Environment of deposition 1. River emerging onto a semi-arid plain Appropriate letter (A or B) 2. Beach (marine) 3. Coral lagoon 4. Deep marine basin (d) Describe, giving the evidence, the likely post-depositional history of Rock B. [3] Total 15 marks Turn over.

4 4 Examiner 2. Figure 2a is a phase diagram showing the experimental crystallisation of plagioclase feldspar over a range of compositions (from Na-rich Albite to Ca-rich Anorthite). P Temperature ( C) composition of liquid composition of crystals Albite Plagioclase composition Anorthite NaAlSi 3 O 8 CaAl 2 Si 2 O 8 (calcium deficient) % calcium in Na:Ca ratio (calcium rich) Figure 2a (a) Name the variety of plagioclase feldspar to crystallise at the highest temperature. [1]... (b) Melt P on Figure 2a has the composition of 35% sodium (Na) rich plagioclase : 65% calcium (Ca) rich plagioclase. Complete the table below to show the crystallisation characteristics of melt P as it cools, assuming that the melt remains in equilibrium with the crystals that form. [5] Melt P 35% Na : 65% Ca Temperature of melt ( C) Composition of melt (% Na: % Ca) Composition of crystals (% Na: % Ca) Initial crystallisation 35:65 Crystallisation at 1400 C :75 Final crystallisation

5 (c) Figure 2b is a polished surface showing the texture of an igneous rock. 5 Examiner Figure 2b With reference to Figure 2a and to the zoned plagioclase crystal (X) in Figure 2b, (i) state the probable difference in composition of zones I and II, [1] account for this variation in composition. [3] (d) Explain why the plagioclase crystals of the groundmass are not zoned. [2] (e) From your knowledge, describe one process during the emplacement or crystallisation of an igneous rock that would produce a magma with a different composition from the original melt. [3] Total 15 marks Turn over.

6 6 Examiner 3. Figure 3a is a partly completed block diagram of a dip slip fault. Rocks X and Y are diagrams of rock types found at the localities indicated on the fault plane. N fault plane s X 0.25m limestone clasts calcite Y 0.1m Depth (m) shale limestone s shale dolerite relative fault movement Figure 3a (a) (i) Complete the table below to describe the fault characteristics. [4] Fault characteristics Description Strike direction Downthrow direction Amount of strike-slip movement NONE Principal stress component (s - min, int, max) (parallel to strike direction) Type of fault Complete the top surface of Figure 3a to show the probable outcrop of the shale and dolerite to the north of the fault outcrop. Clearly label your outcrops. [2] (b) Rocks X and Y were both formed at the same time. (i) Describe the texture of rock X. [3]

7 7 Examiner Account for the differences in texture of rocks X and Y with reference to their behaviour during fault movement. [2] (c) Figure 3b is a photograph of an exposed vertical face of a fault plane at another locality. Figure 3b (i) Name the structures exposed on the fault plane. [1] Critically assess the use of these structures in determining the fault movement. You may wish to annotate Figure 3b. [3] Total 15 marks Turn over.

8 8 Examiner 4. Flood basalts events and meteorite impacts have both been linked with the end-permian (P-T) and Cretaceous-Tertiary (K-T) mass extinctions. (a) Explain what is meant by a mass extinction. [2] Key to graph Flood basalt Mass extinction Ages of mass extinction events (Ma) Source: Evolutionary catastrophes - V. Courtillot, Cambridge Columbia Ethiopia Mass extinction events North Atlantic Deccan Madagascar Rajmahal Etendeka End of lower Oligocene Middle Miocene End of Cenomanian End of Paleocene South Africa (Karoo) NE America End of Jurassic End of Aptian End of Triassic Bajocian Ages of flood basalt events (Ma) Siberian End of Permian (P-T) End of Cretaceous (K-T) Figure 4a Refer to Figure 4a. (b) (i) In the box below, name the flood basalt event to correlate with the age of the K-T and P-T mass extinctions. [2] Mass extinction age Name of flood basalt event K T extinction (~65 Ma) P T extinction (~250 Ma) Describe the degree of correlation between the age of flood basalt events and mass extinctions over the last 300Ma. [3]

9 9 Examiner Figures 4b - 4d show data obtained at the K-T boundary Position relative to K-T boundary (cm) Danian marls Maastrichtian marls Sedimentary sequence Black clay K-T 0 boundary Iridium concentration Meteorite spinel crystals High % Organic content Concentration of cosmic inclusions 50 0 Source: The end of the dinosaurs - C. Frankell, Cambridge Refer to Figures 4b, 4c and 4d. Figure 4b Figure 4c Figure 4d (c) (i) Describe the distribution of organic material in Figure 4c. [2] Compare the distributions of meteoritic iridium (rare element) and spinel (nickel iron oxides) in Figure 4d. [2] (d) With reference to all data (Figures 4a - 4d), critically evaluate the evidence that a meteorite impact was responsible for the K-T boundary mass extinction event. [4] Total 15 marks Turn over.

10 10 Examiner SECTION B Questions 5-7 relate to the British Geological Survey 1:50,000 Geological Map extract of Stoke-on-Trent. Answer all questions in the spaces provided. This section should take approximately 1 hour to complete. 5. The geological map shows the solid geology. (a) State what is meant by the solid geology. [1]... (b) The unconformity at the base of the Triassic Chester Pebble Bed (CPB) and Kinnerton Sandstone formations (KnS) crops out in the west of the geological map. In the grid square below, draw and label the map evidence for this unconformity from any one appropriate grid square. Carefully label the grid-lines and the position of the unconformity on your map. [3] (c) Refer to the geological map and generalised geological column. (i) Complete the table below to indicate the local dip in Box A on the geological map and the order of superposition of the top two coal seams to be encountered in the abandoned mine shaft at grid reference (GR) [3] Direction Angle of dip (degrees) Name of coal seam Age of coal seam SW Youngest Oldest

11 11 Examiner Briefly suggest a probable reason for the irregular outcrop pattern of Upper Coal Measures (UCM) within grid square [1] (iii) Explain why the outcrop pattern of Upper Coal Measures (UCM) in Box B is v-shaped towards the SE around GR [2] Total 10 marks Turn over.

12 12 Examiner 6. Figure 6 is a sketch of part of the geological map showing structural features. 78 Red Rock Fault N TRIASSIC Barren Measures Coal Measures Western anticline Potteries syncline Apedale Fault 88 Figure 6 (a) Refer to the geological map, cross section and Figure 6. (i) Complete the table below to identify the characteristics of the following folds: 1. Western Anticline 2. Potteries Syncline [3] Fold characteristics Western Anticline Potteries Syncline Axial plane trend Axial plane dip angle (degrees) and direction along section. Fold symmetry Orientation (direction) of the maximum principal stress component (s max ) BOTH : NNE SSW Angle (degrees) Direction Angle (degrees) Direction ~70 NW Both : Both : ESE WNW

13 13 Examiner Using the geological map and generalised geological column, explain why the Western Anticline is classified as an anticline. [2] (iii) On Figure 6, mark both fold axes with an arrow to show the direction in which each fold plunges. [2] (b) (i) The cross section (below grid square 8247) shows the Newcastle Formation (Ncl) aligned with the base of the Upper Coal Measures (UCM) across the Apedale Fault. Using the generalised geological column, calculate the throw (vertical displacement) of the Apedale Fault. Show your working. [2] Throw (vertical displacement)... m Using evidence from the geological map and cross section, evaluate the following statement taken from a student's analysis of the map. The Red Rock Fault (grid square 8050) and the Apedale Fault are both: 1. normal faults, 2. with similar throws, 3. which result from the same principal stresses that formed the Western Anticline and Potteries Syncline folds. [4] Total 13 marks Turn over.

14 14 Examiner 7. Figure 7a is a map of the Stoke-on-Trent area (east of grid line 85) showing ground subsidence mm mm 56 mm 74 mm Line of section Key to map 56 mm mm line joining points of 28 mm ground subsidence mm Figure 7a 0 ground subsidence (mm) grid lines along section Figure 7b

15 15 Examiner Refer to Figure 7a, the geological map, and cross section as appropriate. (a) (i) Complete the graph in Figure 7b to show the variation in ground subsidence along the line of section in the Stoke area. [3] Write a brief account of ground subsidence in the Stoke area. You should describe the distribution and extent of the subsidence in Figures 7a and 7b and suggest a probable human cause. [3] (iii) Give a geological explanation for the variation in subsidence identified. [2] (b) Using your knowledge and evidence from the geological map assess the possible geological hazards associated with building a major housing development on Upper Coal Measure strata (UCM) within grid square [5] Total 13 marks Turn over.

16 16 Examiner