24-Pet-A1 Principles of Stratigraphy and Sedimentation · May 2018
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 17-Pet-A1 Principles of Stratigraphy & Sedimentation, 2018-May. 3 hours duration; closed book, no 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 5 marks each, for a Part B total of 30 marks – an 80-mark maximum (50 for Part A + 30 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, dolomitization); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial/deltaic systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, deep-marine and shelf systems); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, basin classification, 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.
Sedimentary basins are grouped by the plate-tectonic mechanism that creates their subsidence:
| Tectonic regime | Basin type | Description |
|---|---|---|
| Extensional (divergent) | Rift basin | Active crustal extension and thinning along normal faults; typically the first stage of continental breakup |
| Passive margin basin | Forms after rifting proceeds to full continental separation and seafloor spreading begins; the formerly active rift margin subsides thermally | |
| Aulacogen | A failed arm of a three-armed (triple-junction) rift that stops extending once spreading is established on the other two arms; continues to subside and fill as a fault-bounded trough | |
| Compressional (convergent) | Foreland basin | Forms by lithospheric flexure under the load of an adjacent fold-thrust belt |
| Fore-arc basin | Forms between the subduction trench and the volcanic arc, above the subducting slab | |
| Retro-arc (back-arc) basin | Forms on the continentward side of a volcanic arc, commonly by flexural loading of the arc or by localized extension | |
| Strike-slip (transform) | Pull-apart basin | Localized, often rhomb-shaped, rapidly subsiding basin formed at a releasing bend or stepover along a strike-slip fault system |
| Intracratonic (sag) | Intracratonic basin | Broad, slowly subsiding interior-craton depression driven mainly by long-term thermal or lithospheric-loading subsidence rather than active faulting at the time of its main fill; some initiate above an earlier, now-inactive rift |
