18-Geol-A3 Sedimentation and Stratigraphy · December 2017
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Geological Engineering, 04-Geol-A3, Sedimentation & Stratigraphy, 2017-Dec. Closed book, 3 hours, no calculator permitted.
Reference texts: Nichols, Sedimentology and Stratigraphy, 2nd ed. (depositional environments, facies models, flow regime and bedforms, carbonate platforms, stratigraphic principles, correlation, sequence stratigraphy); Boggs, Petrology of Sedimentary Rocks, 2nd ed. (weathering, sandstone and carbonate classification, diagenesis); Allen & Allen, Basin Analysis, 3rd ed. (basin classification, subsurface mapping); Tearpock & Bischke, Applied Subsurface Geological Mapping, 2nd ed. (structure-contour, isopach and lithofacies mapping, syndepositional structures).
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.
| Sub-discipline | Fundamental unit | Defined by |
|---|---|---|
| Lithostratigraphy | Formation | A body of rock unified by distinctive, mappable lithologic character |
| Biostratigraphy | Biozone | Strata characterized by a defined fossil content/range (Question 16 covers the four biozone types) |
| Magnetostratigraphy | Magnetozone (polarity zone) | Strata recording a specific interval of consistent geomagnetic polarity |
| Chronostratigraphy | Stage | The rock record deposited during a specific interval of geologic time (a time-rock, not a time, unit) |
Lithostratigraphic units form a strict hierarchy of rank, each rank built from the one below it:
| Rank | Description |
|---|---|
| Supergroup | Two or more associated groups sharing a broadly similar lithologic character or origin |
| Group | Two or more associated, mappable formations sharing significant lithologic features |
| Formation | The basic, fundamental mappable lithostratigraphic unit — a body of rock with distinctive, consistent lithologic character |
| Member | A named, lithologically distinct part of a formation, not necessarily mapped everywhere the formation occurs |
| Bed | The smallest formally recognized lithostratigraphic unit — a single, distinctive, traceable layer within a member or formation |
