24-Pet-A1 Principles of Stratigraphy and Sedimentation · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 98-Pet-A1 Principles of Stratigraphy & Sedimentation, 2016-May. 3 hours duration; closed book, no calculator permitted. The paper has two parts: Part 1 (Questions 1–12, Sedimentology and Sedimentary Processes – 10 marks each; answer any eight of the twelve, 80 marks total) and Part 2 (Questions 13–20, Stratigraphy and Sedimentary Basin Analysis – 10 marks each; answer any five of the eight, 50 marks total) – a 130-mark maximum (80 for Part 1 + 50 for Part 2).
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, coastal processes); 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.
Dunham's (1962) scheme classifies carbonate rocks by depositional texture – mud content, grain support and whether original components were organically bound – rather than by grain composition. Embry & Klovan (1971/72) extended it to name coarse (>2 mm) allochem fabrics and to subdivide the boundstone category by binding mechanism.
| Term | Support / fabric | Distinguishing feature |
|---|---|---|
| Mudstone | Mud-supported | <10% grains – almost pure lime mud |
| Wackestone | Mud-supported | >10% grains, but grains "float" within a load-bearing lime-mud matrix |
| Packstone | Grain-supported | Grains touch and form the load-bearing framework, but lime mud still fills the intergranular pores |
| Grainstone | Grain-supported | No lime-mud matrix – pores are empty or cement-filled; indicates thorough winnowing |
| Floatstone (Embry & Klovan) | Mud-supported, coarse | >10% grains coarser than 2 mm, "floating" in a finer (mud or grain) matrix |
| Rudstone (Embry & Klovan) | Grain-supported, coarse | Grain-supported fabric of allochems coarser than 2 mm |
| Bafflestone (Embry & Klovan) | Organically bound | Sediment baffled/trapped in place by upright, branching or stalk-like organisms |
| Bindstone (Embry & Klovan) | Organically bound | Sediment bound in place by encrusting/laminar organisms (e.g., algal mats) |
| Framestone (Embry & Klovan) | Organically bound | Rigid, in-place skeletal framework built by colonial organisms (corals, stromatoporoids, rudists) |
