18-Geol-A3 Sedimentation and Stratigraphy · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Geological Engineering, 04-Geol-A3, Sedimentation & Stratigraphy, 2018-May. Closed book, no calculator, 3 hours, 80 marks total. Part 1 (Questions 1–10, Sedimentology and Sedimentary Processes, 50 marks) instructs "Questions 1 and 2 must be answered (10 points each); answer any FIVE of Questions 3–10 (6 points each)." Part 2 (Questions 11–19, Stratigraphy, 30 marks) instructs "Answer any FIVE of Questions 11 to 19 (6 points each)."
Reference texts: Nichols, Sedimentology and Stratigraphy, 2nd ed. (depositional environments, facies models, sequence stratigraphy, biostratigraphy and correlation); Boggs, Petrology of Sedimentary Rocks, 2nd ed. (sandstone and carbonate classification, weathering, diagenesis); Bjorlykke, Petroleum Geoscience: From Sedimentary Environments to Rock Physics, 2nd ed. (basin settings, reservoir facies).
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.
| Continental environments | Marginal marine (transitional) environments | Marine environments |
|---|---|---|
| 1– Fluvial (alluvial channel/floodplain) | 1– Deltaic | 1– Shallow-marine shelf |
| 2– Aeolian (desert dune field) | 2– Estuarine / tidal flat | 2– Deep-marine (submarine fan / abyssal plain) |
Continental: fluvial systems (braided or meandering channels with adjacent floodplain/overbank fines) are deposited entirely above sea level by rivers, while aeolian systems (dune fields, sand sheets, interdune deflation flats) accumulate in arid, wind-dominated settings — both are recognized by exclusively non-marine sedimentary structures and the complete absence of marine trace/body fossils.
Marginal marine (transitional): deltas form where a river debouches into a standing body of water, interfingering fluvial and marine processes (distributary channels, mouth bars, prodelta muds); estuarine and tidal-flat systems occupy drowned river valleys or low-relief coastlines dominated by tidal currents, producing characteristic tidal bundling, flaser/wavy/lenticular bedding and a mix of brackish-tolerant fauna.
Marine: the shallow shelf (above storm/fair-weather wave base) is dominated by wave and storm reworking, bioturbation and a normal-marine fauna, grading offshore into the deep-marine realm — submarine fans and the abyssal plain — dominated by turbidity-current (Bouma-sequence, Question 8) and hemipelagic/pelagic deposition far below any wave influence.
