24-Pet-A1 Principles of Stratigraphy and Sedimentation · Undated paper
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 17-Pet-A1 Principles of Stratigraphy & Sedimentation, 2019-May. 3 hours duration; closed book, approved Sharp/Casio calculator permitted. The paper has two parts: Part A (Questions 1–10, Sedimentology and Sedimentary Processes) – Questions 1 and 2 are mandatory (10 marks each, 20 marks), plus any five of the remaining eight (3–10) at 6 marks each (30 marks), for a Part A total of 50 marks; and Part B (Questions 11–19, Stratigraphy and Sedimentary Basin Analysis) – answer any six of the nine at 6 marks each, for a Part B total of 36 marks – an 86-mark maximum (50 for Part A + 36 for Part B).
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 (sandstone/carbonate classification, diagenesis, porosity); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial/deltaic/deep-marine systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, alluvial fans, deltas, deep-marine systems); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (basin analysis, well-log correlation, seismic/acoustic impedance); 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.
Definitions. A conglomerate is a lithified gravel (>2 mm clasts) in which the clasts are predominantly rounded, recording significant transport/abrasion. A breccia is a lithified gravel with predominantly angular clasts, recording minimal transport or a non-fluvial (mechanical) origin. A diamictite is a non-sorted or very poorly sorted terrigenous rock containing clasts spanning a wide size range (clay to boulders) set in a muddy/sandy matrix; the term is purely textural/descriptive and carries no genetic implication – a diamictite can be a tillite (glacial), a debris-flow deposit, or a mass-wasting deposit, and its true origin must be established from other evidence (striated/faceted clasts, associated facies) before a genetic name is applied.
| Rock | Process | Diagnostic character |
|---|---|---|
| Conglomerate | Fluvial channel-lag/bar | Imbricated, rounded clasts; sorting depends on transport distance |
| Beach/shoreface gravel | Well-rounded, well-sorted by wave winnowing/reworking | |
| Glaciofluvial outwash | Rounded, stratified, deposited by meltwater beyond the ice front | |
| Breccia | Talus/scree (sedimentary) | Angular clasts at a slope base; essentially no lateral transport |
| Fault/tectonic breccia | In-situ shattering of rock along a fault zone | |
| Collapse/solution breccia | Roof collapse over a cave, or founder of strata over dissolved evaporite/carbonate | |
| Volcanic breccia | Fragmental pyroclastic ejecta, or autobrecciation of a cooling lava flow | |
| Intraformational (edgewise) breccia | Storm/current reworking of penecontemporaneous, still-soft mud rip-up clasts – angular, very short transport |
