WJEC Geology GL5 Quaternary Geology — Papers & Mark Schemes

Oxygen isotope analysis is central to Quaternary geology. Understand the principle: during glacial periods, light oxygen-16 is preferentially locked in ice sheets, enriching ocean water (and marine fossils) in heavy oxygen-18. The resulting δ18O curve from deep-sea sediment cores provides a continuous record of global ice volume. Practise reading these curves: higher δ18O values indicate glacial conditions, lower values indicate interglacial warmth. Glacial landform questions test your ability to connect process to product. For erosional landforms (cirques, arêtes, U-shaped valleys, roches moutonnées), explain the specific processes — plucking, abrasion, freeze-thaw weathering — that created each feature. For depositional landforms (moraines, drumlins, eskers, outwash plains), explain how ice dynamics and meltwater behaviour controlled sediment deposition. Sea-level change questions require distinguishing between eustatic (global, driven by ice volume and ocean temperature), isostatic (local, driven by crustal loading and unloading), and tectonic causes. Know how raised beaches, submerged forests, and drowned river valleys provide evidence for relative sea-level change, and how to interpret shoreline displacement diagrams.