24-Pet-A1 Principles of Stratigraphy and Sedimentation · December 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 98-Pet-A1 Principles of Stratigraphy & Sedimentation, 2014-Dec. 3 hours duration; closed book, no calculator permitted. The paper has three parts: Part A1 (Questions 1–7, sedimentary processes, 5 marks each, answer any 4 of 7 for 20 marks), Part A2 (Questions 8–15, brief/multiple-choice, 3 marks each, answer any 5 of 8 for 15 marks), and Part B (Questions 16–24, stratigraphy, 5 marks each, answer any 6 of 9 for 30 marks) – a 65-mark maximum.
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 (carbonate classification, diagenesis, dolomitization); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (fluvial systems, sequence stratigraphy, stratigraphic units); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models, trace fossils); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rocks, 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.
Lithostratigraphic units are rock bodies distinguished and delimited purely on the basis of observable lithological (physical/mineralogical) character – independent of age, fossil content, or time significance – and are organized in a formal hierarchy of four ranks:
| Rank | Definition |
|---|---|
| Supergroup | Two or more associated groups sharing significant lithological features, grouped for convenience of regional description. |
| Group | Two or more associated, contiguous or interbedded formations with unifying lithological character; the fundamental unit for regional mapping/correlation. |
| Formation | The FUNDAMENTAL, basic mappable unit of lithostratigraphy – a body of rock identified by distinctive, consistent lithological character (or a distinctive combination of characters) that distinguishes it from adjacent units, mappable at the Earth's surface or traceable in the subsurface. |
| Member | A named lithologically distinct subdivision of a formation, not necessarily mappable everywhere the formation is present. |
| Bed | The smallest formal lithostratigraphic unit – a distinctive, usually thin, single layer identifiable within a member or formation (e.g. a marker bed, a coal seam). |
The Formation is the basic unit of the whole hierarchy – every group is built up of formations, and members/beds are optional finer subdivisions used only where extra resolution is practically useful, so a rock succession can, at minimum, always be validly described purely in terms of formations even where no formal members or beds have been designated.
