SOUTH EASTERN KENYA UNIVERSITY
UNIVERSITY EXAMINATIONS 2014 / 2015
THIRD YEAR EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE IN GEOLOGY
SGL 303:
DATE:
SEDIMENTARY PETROLOGY
24TH APRIL 2015
INSTRUCTIONS:
•
Answer ALL Questions From SECTION A.
•
Answer any TWO Questions from SECTION B
•
Illustrate your answers by means of carefully drawn sketches and diagrams.
TIME: 2Hours
SECTION A (30 MARKS)
1.
Explain the Principle of Faunal Succession
(3Mrks)
2.
Identify and explain the THREE kinds of system tracts
(3Marks)
3.
List THREE economic minerals commonly found within delta depositional environments
(3Marks)
4.
Describe the FOUR main types of coal
5.
Highlight the FIVE attributes or characteristics of grains observed when classifying
sediments or sedimentary rocks
6.
(4Mrks)
(5Marks)
The river shown in the diagram below carries sediments composed of sand, silt and clay.
The table that follows gives the percentage share of the total mass of sediment carried at a
particular height above the river bed.
Figure 1: sediment flow in river
Figure 2: Share of mass of sediments above river bed
a.
i. Complete the table above by computing the values of (a) and (b) to show the percentage
share of clay that is carried at 2 and 3 metres above the river bed
(1Mark).
ii. Using the attached graph paper plot a graph to show the percentage of sand, silt and clay
carried at each height above the river bed
(4Marks).
iii. Describe the general relationship shown by the graph for silt
(1Mark)
iv. Explain why the greatest mass of sediment being transported by the river is within the
first metre above the river bed
7.
(1Mark).
Referring to the case study you did during course work, outline the main contents of the
study based on the following guidelines;
Title of the study, Geological setting, main objective of the study and what geo-scientific
problems it solves, location of the study, geo-scientific method(s) used to test explore,
Results and conclusion
(5Marks)
SECTION B (40 MARKS)
1. Two boreholes A and B were sunk to establish the stratigraphy of a coastal area. The
stratigraphy for borehole A is given in column A (Fig4) below and besides it column B is
blank.
a.
i. Using the information given in the table below (Fig 3) complete the diagram (column
B) for borehole B (Fig 4)
(3Marks)
Figure 3: Information for borehole B
Figure 4: Stratigraphic correlation for borehole A&B
ii. Draw lines between the column for borehole A and B to correlate the sequence of
rocks
(2Marks)
iii. Give a brief geological history of the area
(2Marks).
b. Distinguish between bedding and lamination
(4Marks)
c. Explain the use of ‘heavy minerals’ in provenance studies
(9Marks)
(i) Discuss the FIVE different modes of physical weathering
(ii) Identify the THREE categories of inorganic sedimentary structures
(17Marks)
(3Marks
2.
3. Consider the diagram below (Fig 5) and answer the following questions
Figure 5: Combined depositional environments
a.
(i) How was feature Q formed?
(1Mark)
(ii) What feature suggests that the flints were formed after the chalk? (1Mark)
(iii) Give two pieces of evidence that suggest that bed P was deposited in a delta and
not in a desert environment
(2Marks)
b. Outline the FIVE zones that beach environments can be divided into. (5Marks)
c. Distinguish between Volcaniclastics and Pyroclasts
d. Distinguish between debris flow and turbidite deposits
(2Marks)
(4Mark)
e. With the aid of a diagram explain the stratigraphic order of the FOUR main horizons
of a soil profile
(5Marks)
4.
a. Deltas are classified into three main categories namely; fluvial-dominated, tide
dominated, and Wave-dominated. Write brief notes on any TWO of these categories
(10Marks)
b. Outline the SIX modes of sediment grain movement in a body of water (3Marks)
c. Explain the difference between sedimentology and stratigraphy
(4Marks)
d. Distinguish between Arenites and Wackes
(3Marks)
5.
a) Identify and briefly explain the THREE classifications of carbonate sediments and
sedimentary rocks
(6Marks)
b) Explain the formation of evaporites and identify at least FOUR examples giving their
economic importance
(4Marks)
c)
i. Name and describe the type of structures shown in the photos bellow (Fig 6&7)
below giving the number of unconformities depicted
(2Marks)
Figure 6
Fig 7
ii. State the type of ancient depositional information that can be extracted from the
structure in the photo Fig 7 above
(1Mark)
d) With the aid of diagrams, if necessary, describe the different possible types of
grading in beds
(2Marks)
a. Study Fig 7 below and answer the questions that follow
Figure 7
(i) All the columns above have one thing in common. What is it
(1mark)
(ii) Identify and explain the columns which show:
(2Marks):
1. Long break in sedimentation period(record)
2. Short break in sedimentation period(record)
(iii) Apart from the break in sedimentation period, some of the figures can be grouped
together based on their relationships. Identify TWO different possible categories and
distribute the members accordingly explaining your decision
(2Marks):
Graph paper for Question 6 Section A