24-Pet-A1 Principles of Stratigraphy and Sedimentation · May 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
EGBC National Exam — Petroleum Engineering, 98-Pet-A1 Principles of Stratigraphy & Sedimentation, 2013-May. 3 hours duration; closed book, no calculator permitted. Candidates answer any 10 of the 15 questions (10 marks each, 100 marks total) and are asked to illustrate answers with drawings wherever possible.
Reference texts: Boggs, S. Jr., Principles of Sedimentology and Stratigraphy, 5th ed., Pearson (texture classification, evaporites, clay minerals, sediment gravity flows, storm/shelf processes, bedforms, stable isotopes, geological time scale); Tucker, M.E., Sedimentary Petrology, 3rd ed., Blackwell (carbonate fabric, dolomitization, reef facies); Nichols, G., Sedimentology and Stratigraphy, 2nd ed., Wiley-Blackwell (depositional systems, transgression/regression, sequence stratigraphy); Reading, H.G. (ed.), Sedimentary Environments: Processes, Facies and Stratigraphy, 3rd ed., Blackwell (facies models); Selley, R.C. & Sonnenberg, S., Elements of Petroleum Geology, 3rd ed., Academic Press (source rock maturation, petroleum systems); 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.
The geological time scale (chronostratigraphy, Question 7) divides Earth's 4.54-billion-year history into a nested hierarchy of eons, eras, periods (and finer epochs/ages), each boundary fixed by international agreement at a GSSP wherever a well-preserved marker exists, or by a numerical (radiometric) age where no continuous rock record does.
| Boundary | Age (Ma) |
|---|---|
| Earth's formation (start of Hadean) | ≈4540 |
| Hadean–Archean | ≈4000 |
| Archean–Proterozoic | 2500 |
| Precambrian–Phanerozoic (base Cambrian) | 541 |
| Ordovician–Silurian–Devonian–Carboniferous | 485 / 444 / 419 / 359 |
| Paleozoic–Mesozoic (Permian–Triassic) | 252 – the end-Permian mass extinction, Earth's largest |
| Triassic–Jurassic–Cretaceous | 201 / 145 |
| Mesozoic–Cenozoic (Cretaceous–Paleogene) | 66 – the end-Cretaceous (dinosaur) mass extinction |
| Paleogene–Neogene–Quaternary | 23 / 2.58 |
The three Precambrian eons (Hadean, Archean, Proterozoic) together span roughly 88% of Earth history yet are divided into far fewer named units than the last 541 million years (the Phanerozoic, "visible life"), simply because complex, readily fossilizable organisms – the basis for fine biostratigraphic subdivision – did not exist before the Cambrian explosion; Precambrian time is instead subdivided chronometrically (by numerical age) rather than biostratigraphically.
