Lacustrine Sediment

Lacustrine sediment is material deposited in a lake, distinct from marine and fluvial sediment by its still-water setting and freshwater fauna. It is typically fine-grained mud and silt, often finely laminated, and can preserve annual layers called varves that give a year-by-year record. Organic-rich lake muds, diatomite, and carbonate marls are common types. In coastal and continental-margin sequences, lacustrine layers mark former lakes drowned by a marine transgression or isolated behind a barrier, so they help reconstruct sea-level and environmental change. Cores through such layers let analysts separate freshwater from marine phases in a margin’s history.