Sandstone Formation: Burial Compaction & Cementation (2D)

Deposition & Burial

Initial porosity φ₀ 40%

Deposition rate 300 m/Myr

Diagenesis

Compaction coeff. c (Athy's law) 0.55 /km

Cementation rate k 0.020 /Myr

Live Readout

Geologic time

0.0 Myr

Burial depth

0 m

Surface porosity

40.0%

Deepest porosity

40.0%

Layers buried

Cement loss (base)

0.0 pp

How it works

Each new sand layer buries the ones beneath it, adding overburden. Porosity is driven by two independent diagenetic processes acting on every buried layer:

Compaction (Athy's law):
  φ_mech(z) = φ0 · e^(−c·z)     z in km

Cementation (1st-order precipitation
kinetics, driven by time-in-burial t):
  φ(z,t) = φ_mech(z) · e^(−k·t)   t in Myr

Compaction depends only on current burial depth — mechanical grain rearrangement under the weight of everything deposited above. Cementation depends only on time spent buried — pore-fluid mineral precipitation is a slow chemical process, so an old, slowly-buried layer cements more than a young one at the same depth. Raising the deposition rate buries sand faster, which lowers cementation (less time to precipitate) but raises compaction sooner (depth grows faster) — a real trade-off geologists use to read burial history from porosity logs.

Cross-section — stratigraphic column; colour = current porosity of each bed (pale = porous sand, dark = tightly cemented sandstone).
Porosity–depth chart — dashed line is the instantaneous compaction-only trend (Athy's law); the solid line is the actual modelled porosity of every deposited layer, including its own cementation history.

High porosity (loose sand) Low porosity (cemented rock) Athy's-law reference (dashed)