Correct Order of Paleozoic Periods: 24-Pet-A1 Principles of Stratigraphy and Sedimentation, December 2014, Q23

Question 23 of 24: Correct Order of Paleozoic Periods

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

Notes on this paper

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 23: Correct Order of Paleozoic Periods (5 marks)

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.

Answer: (c) Cambrian → Ordovician → Silurian → Devonian → Carboniferous → Permian. This is the standard, ICS-defined order of the six Paleozoic periods from oldest to youngest, with approximate base ages: Cambrian (541 Ma) → Ordovician (485 Ma) → Silurian (444 Ma) → Devonian (419 Ma) → Carboniferous (359 Ma) → Permian (299 Ma, ending at the 252 Ma Permian–Triassic boundary). All four distractors reorder two adjacent periods relative to this sequence: (a) and (e) both place Devonian first, ahead of Cambrian; (b) swaps Devonian and Carboniferous (placing Carboniferous, the younger period, before Devonian); and (d) swaps Devonian and Silurian relative to Carboniferous. (Note: options (b) and (c) are distinct, differing in whether Devonian precedes or follows Carboniferous, and only (c) is correct.)

Topic. Paleozoic period order and the geological time scale.

Key relations. Cambrian → Ordovician → Silurian → Devonian → Carboniferous → Permian (541–252 Ma), the six Paleozoic periods in ICS-defined order.

Why this works. The period boundaries are defined by GSSP markers tied to specific biostratigraphic and, where possible, radiometric age control, giving a single internationally-ratified order that is not open to interpretation – memorizing it (e.g. via a mnemonic such as "Camels Often Sit Down Carefully, Perhaps Their Joints Creak") is a standard exam-preparation aid.

Common pitfall. Confusing the order of Devonian, Silurian and Carboniferous – these three are the periods most often transposed by candidates; anchoring on "Devonian = the age of fishes, between the Silurian (early land plants) and the Carboniferous (coal swamps/amphibians)" helps fix the correct middle-Paleozoic order.

Source. International Commission on Stratigraphy, International Chronostratigraphic Chart.