Slumping in the chalk
A slumping indicates the travel of a mass of laminated, partially strengthened sediments, under the influence of the gravity, following a slope of the sea bed. During this travel, deformations (wrinklings, cuttings) affect the slid mass which takes the name of slump.
In broad outline, the slumping can be:
- Translationnel, when the travel is made according to a plane surface, generally a plan of stratification;
- Rotational, when the discontinuity surface is concave upward, splitting the stratification.
In reality, most of the slumpings are mixed.
The upstream part of the slump (or head) contains generally one or several concave steep slopes, scars of tearing and strata coiled (pinch and swell structure))
The part approval (or foot) contains folds and overlappings propagating chronologically towards the approval.
The submarine slumps is often activated by a fast variation of the interstitial pressure, for example a wave of tide or a seismic shaking.
Slidings synsédimentaires (slumping) in the chalk
The chalk is a sediment particularly sensitive to the break, because it is porous and its essential particles very weakly cemented only.
The most beautiful examples of slumping observe in the case of a sedimentary trained bottom of "hillocks and basins", particularly developed in upper Turonien - lower Coniacien of the Block of Callus. Multiple examples are present since the valley of the Seine (careers of Tancarville) until Yport. The majority of slumpings are introduced on the more stiff side is from hillocks.