Stratigraphic unit

Geological and lithological features

BARRIER IV

Lagoonal deposits

Fine-grained sands and silts interlayered with variable proportions of organic matter and clay being deposited close to Lagoa dos Patos.

Dunefield Barrier

Transgressive Dune Sheets (TDS) and Transgressive Dunes (TD) developed by NE onshore winds.

Alluvial fan

Fans of sand due to erosion by drainage cutting across the fault escarpment.

Beach ridges

Narrow and very elongated sand ridges, intercalated with narrow depressions of mud and marsh, both parallel to shoreline.

Pleistocene Barrier III

Fine to medium-grained sands, mostly horizontal, parallel stratification, slightly compacted, and impregnated by Fe³⁺ hydroxides and clay.