Geology of Kent

The geology of Kent in southeast England largely consists of a succession of northward dipping late Mesozoic and Cenozoic sedimentary rocks overlain by a suite of unconsolidated deposits of more recent origin.

These ridges are the remains of the Wealden dome, a denuded anticline across Kent, Surrey and Sussex, which was the result of uplifting caused by the Alpine movements between 10-20 million years ago.

[5] Dartford, Gravesend, The Medway Towns, Sittingbourne, Faversham, Canterbury, Deal and Dover are built on chalk.

[4] The Hastings Beds, which are resistant to weathering, leading to outcrops, such as High Rocks Tunbridge Wells, and sterile soil only suited to heathland and forests of Scots Pine.

The Wealden dome is a Mesozoic structure lying on a Palaeozoic foundation, which usually creates the right conditions for coal formation.

[10] The river is tidal as far as Allington lock, but in earlier times cargo-carrying vessels reached as far upstream as Tonbridge.

The oldest rocks to appear at the surface in Kent are the mudstones, limestones, siltstones and sandstones of the Wealden Group which underpin the wooded landscape of The Weald.

These are in turn overlain by the sandstones of the Lower Greensand Group, the Upper Greenstone Formation and the mudstone of the Gault.

The Thanet Formation is the oldest of these and occupies an area from the coast near Sandwich east through Canterbury to Sittingbourne, Rochester and, intermittently, to Dartford.

North of this outcrop, and stratigraphically above it, is a thinner band of pebbly, shelly sands and clays ascribed to the Lambeth Group.

The youngest Palaeogene strata is a patch of late Eocene sand, silt and clay around Eastchurch and Minster on the Isle of Sheppey.

The fold arises from the continuing Alpine orogeny and results in the general northward dip of the rock strata in most of Kent.

There are extensive spreads of coastal and estuarine alluvium on the Thames Estuary coast, in the low ground surrounding the Isle of Thanet and across Romney Marsh.

Loessic deposits, of Aeolian origin, i.e., windblown, are common in east Kent, especially on the northern slopes of the Downs where they are known as brickearths.