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.
Each phrase (i–xii) matches exactly one term (a–l):
| Phrase | Term | Why it matches |
|---|---|---|
| i. Sloping surfaces of prograding strata | k) Clinoform | A clinoform is precisely the inclined depositional surface (and the body of strata built on it) produced by lateral (progradational) sediment supply, e.g. a delta-front or shelf-margin slope |
| ii. Zone where sediments can accumulate | l) Accommodation space | Accommodation space is defined exactly as the available space, below base level, for sediment to fill |
| iii. Equivalence of rock units of similar lithology and stratigraphic position | d) Lithocorrelation | Lithocorrelation is correlation based on matching lithology/rock character between sections |
| iv. Boundary of a unit whose age differs by location | e) Diachronous | A diachronous boundary is, by definition, one whose age varies from place to place (e.g., a migrating shoreline sand) |
| v. Minor gap shorter than biostratigraphic resolution | i) Diastem | A diastem is defined in the stratigraphic codes as a depositional pause too brief to be resolved biostratigraphically – distinct from a true unconformity |
| vi. Similarity of fossil content and biostratigraphic position | c) Biocorrelation | Biocorrelation is correlation based on matching fossil content/biostratigraphic position |
| vii. Landward migration of the shoreline | f) Transgression | Transgression is defined as landward shoreline migration (relative sea-level rise outpacing sediment supply) |
| viii. Identifying correspondence of strata in age | a) Chronocorrelation | Chronocorrelation (time correlation) matches strata by age rather than by lithology or fossil content |
| ix. Lithodemic unit next higher than lithodeme | j) Suite | In lithodemic (igneous/metamorphic) classification, a suite is the rank immediately above a lithodeme, analogous to a formation in stratified-rock nomenclature |
| x. Classification, nomenclature, correlation, interpretation of stratified rocks | b) Stratigraphy | This phrase is the standard definition of the discipline of stratigraphy itself |
| xi. A unit that wedges out beyond its parent unit's boundary | g) Tongue | A tongue is a subdivision of a formation that extends (wedges out) beyond the main body of the unit it belongs to, into another unit |
| xii. Combination of several reference sections to demonstrate range/totality of a unit | h) Composite-stratotype | A composite stratotype is used precisely when no single exposed section demonstrates the full range of a stratigraphic unit, so multiple reference sections are combined |
