Herringbone Cross-Lamination: 24-Pet-A1 Principles of Stratigraphy and Sedimentation, December 2014, Q10

Question 10 of 24: Herringbone Cross-Lamination

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 10: Herringbone Cross-Lamination (3 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.

Herringbone cross-lamination is a distinctive structure in which successive cross-bed sets dip in opposing (roughly 180° reversed) directions, giving a herringbone-like pattern in vertical section. It forms where bedform migration direction periodically reverses under a bidirectional current regime – most diagnostically, the flood and ebb phases of a tidal current reworking sand waves or dunes in a tidal channel or tidal sand bar. Because a river or a unidirectional wind can only build cross-sets dipping one way, herringbone cross-lamination is one of the most reliable single indicators of a tidally-influenced depositional environment (tidal flat, estuary, tidal delta).

Topic. Herringbone cross-lamination as a tidal indicator.

Key relations. Opposed-dip cross-sets → bidirectional flow reversal → tidal (flood/ebb) current regime.

Why this works. A cross-bed's foreset dip direction records the migration direction of the bedform that built it; only a genuinely reversing current (as opposed to a unidirectional river or wind, or even a wave-dominated setting without strong net reversal) can build two directly-opposed sets in vertical succession at one location.

Common pitfall. Assuming any two opposed cross-set dips prove tidal influence – a single reversal could reflect a local, one-off flow change (e.g. channel avulsion); a genuinely diagnostic herringbone signature requires a REPEATED, cyclic alternation, ideally paired with other tidal indicators (mud drapes, rhythmic bundling).

Source. Nichols, Sedimentology and Stratigraphy, 2nd ed., ch.12 (tidal environments); Boggs, Principles of Sedimentology and Stratigraphy, 5th ed., ch.8.