Department of Civil & Environmental Engineering CVNG 1011 Geology ASSIGNMENT Due

Question

Department of Civil & Environmental Engineering CVNG 1011 Geology ASSIGNMENT Due Date: Monday 23 March, 2018 before 12:30 pm The information you'll need for this lab is, for the most part, in the course notes and in the extra reading material posted on the course website but you will need to dig around for some more background information, and you will need to use some engineering judgement to answer some of the questions. Consider the following geologic and stratigraphic features. Sequence of Events: The diagram above shows several types of rock bodies, unconformities, and crosscutting relationships. The major rock bodies, faults, and unconformities are labelled by letters, each representing a significant geologic event. These are shown in alphabetical, not chronological order in the column below. Study the diagram and list these events in their proper chronological order. Briefly justify your choice. Say why it is in that order giving reasons etc. A Inclined sequence of sedimentary rockG Igneous intrusion of dolerite B Igneous intrusion of granite C Erosional surface H Volcanic cinder cone Alluvial fan JLava flow K Erosional surface intrusion of granite E Metamorphic rock s intrusion of dolerite L Horizontal

Explanation / Answer

From the principle of cross cutting relationship we can infer the relative age of a bed or layer as the principle states that any rock layer or unit which cross cuts another layer or unit is younger than the layer which it cuts across. Again from the principle of horizontality, we know that under normal conditions, due to the action of gravity, layers of sediments are deposited originally in horizontal layers with the oldest layer neing at the bottom followed by the youngest layer being deposited at the top of the sequence. Using these two principles we can determine the relative age of the events. The igneous intrusion of granite (B) and (D) along with the Metamorphic rock (E) forms the basement and are located at the bottom which implies they are the oldest followed by the erosional surface (K) above it and the sedimentary rock sequence (A) deposited above it. The upper boundaries of the igneous intrusion of dolerite(F) and the sedimentary sequence (A) is truncated by the erosional surface (C) which implies A and F are older than the erosional surface (C). The sedimentary layers (L) have been deposited above the erosional surface (C) and the alluvial fan (I) overlies L, implying L is younger than C and I is younger than L. The igneous intrusion of dolerite (G) cuts across all the layers of A, C, L and reaches the surface which means G is younger than all of these layers. The lava flows lies above the alluvial fan thus implying that the flows are younger.

Thus, the sequence of the events in chronological order (from oldest to youngest) are:

Metamorphic rock (E)

Igneous intrusion of granite (B)

Igneous intrusion of granite (D)

Erosional surface (K)

Inclined sequence of sedimentary rocks (A)

Igneous intrusion of dolerite (F)

Erosional surface (C)

Horizontal sedimentary sequence (L)

Alluvial fan (I)

Igneous intrusion of dolerite (G)

Volcanic cinder cone (H)

Lava flows (J)

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