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.
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. Contour lines depicting thickness of a formation/rock unit | l) Isopach map | An isopach map shows lines of equal true stratigraphic thickness of a specified unit |
| iii. Sedimentary data reflecting paleoslope and sediment-source direction | d) Paleocurrent analysis | Paleocurrent analysis plots directional sedimentary data (cross-bed dips, ripple/flute orientation) to reconstruct paleoslope and provenance direction |
| 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 a depositional pause too brief to be resolved biostratigraphically – distinct from a true unconformity |
| vi. Soil horizon preserved in the stratigraphic record | c) Paleosol | A paleosol is a fossil (buried, preserved) soil horizon |
| vii. Seaward migration of the shoreline | f) Regression | Regression is defined as seaward shoreline migration (sediment supply outpacing relative sea-level rise) |
| viii. Intertidal sedimentary structure | a) Herringbone cross-bedding | Herringbone cross-bedding – opposing-dip cross-set pairs produced by reversing flood/ebb tidal currents – is a classic intertidal indicator |
| ix. Lithodemic unit next higher in rank to lithodeme | j) Suite | In lithodemic (igneous/metamorphic) classification, a suite is the rank immediately above a lithodeme |
| x. Study of sedimentary rocks based on stacking patterns from accommodation-space change | b) Sequence stratigraphy | This phrase is the standard definition of the discipline of sequence 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 |
