24-Pet-A1 Principles of Stratigraphy and Sedimentation · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 98-Pet-A1 Principles of Stratigraphy & Sedimentation, 2014-Dec. 3 hours duration; closed book, no calculator permitted. The paper has three parts: Part A1 (Questions 1–7, sedimentary processes, 5 marks each, answer any 4 of 7 for 20 marks), Part A2 (Questions 8–15, brief/multiple-choice, 3 marks each, answer any 5 of 8 for 15 marks), and Part B (Questions 16–24, stratigraphy, 5 marks each, answer any 6 of 9 for 30 marks) – a 65-mark maximum.
Reference texts: Boggs, S. Jr., Principles of Sedimentology and Stratigraphy, 5th ed., Pearson (grain texture, sediment transport, bedforms, carbonate/evaporite systems, sequence stratigraphy, unconformities, stratigraphic principles); Tucker, M.E., Sedimentary Petrology, 3rd ed., Blackwell (carbonate classification, diagenesis, dolomitization); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, trace fossils); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, reservoir quality); International Commission on Stratigraphy, International Chronostratigraphic Chart (geological time scale).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Earth scientists establish relative age using a small set of logically self-evident principles: original horizontality (sediments are deposited in essentially horizontal layers under gravity, so tilted/folded strata were deformed after deposition); superposition (in an undisturbed sequence, the oldest layer is at the bottom and each successive layer above it is younger); lateral continuity (sediment layers extend laterally in all directions until they thin to a natural depositional edge or are cut off, so correlatable units on either side of an eroded valley were once continuous); cross-cutting relationships (a feature that cuts across a rock body – a fault, a dyke, an unconformity surface – must be younger than the rock it cuts); inclusions (a rock fragment included within another rock body must be older than the host rock that encloses it); and faunal succession (fossil assemblages succeed one another in a recognizable, non-repeating vertical order through geologic time, so matching assemblages can be used to correlate and order strata even across widely separated areas without direct physical continuity).
