8/16/2019 Exam Paper 2010

1/4

UL10/

Page 1 of 4

THIS PAPER IS NOT TO BE REMOVED FROM THE EXAMINATION HALLS

UNIVERSITY OF LONDON GL5151 

MSc and Postgraduate Diplomafor External Students

PETROLEUM GEOSCIENCE

Tectonics and Lithosphere Dynamics

Monday 6th June 2011: 2.30 –  4.30 pm

Candidates should answer 3 questions. Each answer should take about 40 minutes.

Use a SEPARATE answer book for each section.

© University of London 2010

8/16/2019 Exam Paper 2010

2/4

UL10/

Page 2 of 4

1. 

This is a question about extended continental margins, those places that are left behindafter a continental rift zone evolves into a new ocean floored by oceanic lithosphere.

a.  Draw a cross section of a magma-poor (or non-volcanic) extended continental

margin, including a vertical and horizontal scale and labels of important features.

(40%)

 b.  Explain what process is thought to be responsible for the absence of the lower

crust in the outer parts of margins like these. (20%)

c.  With reference to observations from the East African rift zone, what mechanism

dominates the accommodation of plate divergence in settings like these? (20%)

d.  Suggest ways in which the development of such margins might influence the

 petroleum systems that develop in them. (20%)

2.  This is a question about the processes that lead to the formation of sedimentary basins on

top of the lithosphere.

a.  Reflection seismic surveys through two sedimentary basins show that each is

symmetrical, with a deep central portion and shallower edges. The data are not

clear at depths much below the top of basement, making it difficult for you to tell

anything much about the crustal structure in each case. From looking at the basin

fill, you know however that one of the basins formed by stretching of the

lithosphere, the other by flexure of the lithosphere. For both basins, sketch and

label the various sedimentary sequences, and the time they took to accumulate.

(40%)

 b. 

You also have two gravity profiles, one each crossing each of the two basins. Thegravity profiles confirm your interpretation of one basin forming by extension, the

other by flexure. Sketch the two gravity profiles. (20%)

c.  With reference to the likely subsidence history you would observe in a basin of

each type, what kind of organic rich rocks might you expect to accumulate in each

case? (20%)

d.  With reference to the different tectonic origins of the two basins, would you

expect structural or stratigraphic traps to dominate petroleum systems in each

case? (20%)

3.  This is a question about the tectonics of the Tibetan Plateau.

a. 

In the 1980s, movements of parts of the Tibetan Plateau along prominentstrike-slip faults were famously modelled in the laboratory with the use of

‘plasticene’ modelling clay. How was the experiment interpreted in terms

of the process by which continental convergence in the India-Eurasia

collision zone is accommodated? (25%)

 b.  Sometime later, numerical modelling also recreated some of the features of

the plateau quite convincingly, but started by assuming the continental

convergence was accommodated by a very different process: describe the

 process and how the strike-slip faults may have been related to it. (35%)

c. 

Measurements made with GPS equipment have also been used to test these

two models; what have they shown? (20%)

8/16/2019 Exam Paper 2010

3/4

UL10/

Page 3 of 4

d.  Why might GPS measurements taken at the top surface of the upper crust

 be difficult to interpret in terms of the second (numerical) model for

convergence-related processes? (20%)

4.  This is a question about making and using paleogeographic maps.

a. 

Draw sketches illustrating how to use Euler rotations when creating paleogeographic maps for times during the last 180 million years, using

multiple fracture zones (10%) and magnetic anomalies (10%).

 b.  Why are paleogeographic maps showing times before 180 Ma less reliable?

(40%)

c.  The attached paleogeographic map (Figure 1) shows the South Atlantic

Ocean at 118 Ma. At the present day the Walvis Ridge is a submerged

 basaltic ridge, about 2-4 km deep, from which volcanic samples dating to

~130-120 Ma have been dredged. What significance might all this

information have for petroleum systems in the region north of the Walvis

Ridge? (40%)

8/16/2019 Exam Paper 2010

4/4

UL10/

Page 4 of 4

5.  This is a question about the places on Earth where continents on two neighbouring

 plates collide with each other.

a. 

Why is it that continental convergence can come to be accommodated over

very wide collision zones that do not resemble the narrow plate boundaries

seen in many other regions on Earth? (40%)

 b. 

Sketch or describe in words the ways in which continent-continentconvergence is accommodated in the following regions:

i) 

the Zagros mountains (15%);

ii) (NE Iran around the Dasht e Lut desert (15%),

iii) the Tibetan Plateau. (20%)

c.  Describe how the particular response to collision in the Zagros has helped

shape the petroleum system there. (10%)

END OF PAPER