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Earth and Space Sciences · Glossary

What is Condensed section and incised valley?

Also known as: condensed section · incised valley

Definition 16.7 University Earth and Space Sciences — Year 3 · Chapter 16 — Sequence Stratigraphy

A condensed section is a thin interval deposited very slowly far from the shoreline while the sea floods the shelf and the sediment is trapped near the coast: a few centimetres or decimetres of clay, fossils, glauconite or phosphate that may record a long time. An incised valley is a river valley cut into the exposed shelf while relative sea level falls, and filled during the following lowstand and transgression.

Anatomy of a depositional sequence in a dip section (schematic, vertical scale much exaggerated). The sequence boundary (SB, red) is an unconformity on the shelf, with an incised valley, and a correlative conformity in the basin (dashed); here it is drawn above the falling-stage deposits. The transgressive surface (TS) caps the lowstand wedge; the maximum flooding surface (MFS) caps the thin transgressive tract and passes basinward into a condensed section; the highstand foresets downlap onto it.
Anatomy of a depositional sequence in a dip section (schematic, vertical scale much exaggerated). The sequence boundary (SB, red) is an unconformity on the shelf, with an incised valley, and a correlative conformity in the basin (dashed); here it is drawn above the falling-stage deposits. The transgressive surface (TS) caps the lowstand wedge; the maximum flooding surface (MFS) caps the thin transgressive tract and passes basinward into a condensed section; the highstand foresets downlap onto it.
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