Brick clay and limestone are abundant, and there are on the south coast a sand marl rich in phosphates and productive salt deposits.
Geological research shows that the land surrounding the lake consists of gneiss, quartz and schistose rocks, covered, in the higher regions, with marl and red clay, and in the valleys with a rich black loam.
The Chloritic Marl in the Wealden district furnishes much phosphatic material, which has been extensively worked at Froyle.
When the subsoil is too compact to be pervious to water, effectual drainage must be resorted to; when it is very loose, so that it drains away the fertile ingredients of the soil as well as those which are artificially supplied, the compactness of the stratum should be increased by the addition of clay, marl or loam.
The most fertile soils of the state lie in the clay and marl region, a belt from 10 to 20 m.
But not alone has this Leviathan left his pre-adamite traces in the stereotype plates of nature, and in limestone and marl bequeathed his ancient bust; but upon Egyptian tablets, whose antiquity seems to claim for them an almost fossiliferous character, we find the unmistakable print of his fin.
The Maltese Islands consist largely of Tertiary Limestone, with somewhat variable beds of Crystalline Sandstone, Greensand and Marl or Blue Clay.
The oak grows most luxuriantly on deep strong clays, calcareous marl or stiff loam, but will flourish in nearly any deep well-drained soil, excepting peat or loose sand; in marshy or moist places the tree may grow well for a time, but the timber is rarely sound; on hard rocky ground and exposed hillsides.
In the Coralline Limestone the following fossils have been noted :- Spondylus, Ostrea, Pecten, Cytherea, Arca, Terebratula, Orthis, Clavagella, Echinus, Cidaris, Nucleolites, Brissus, Spatangus; in the Marl the Nautilus zigzag; in the Yellow, Black and Greensand shells of Lenticulites complanatus, teeth and vertebrae of Squalidae and Cetacea; in the Sandstone Vaginula depressa, Crystallaria, Nodosaria, Brissus, Nucleolites, Pecten burdigallensis, Scalaria, Scutella subrotunda, Spatangus, Nautilus, Ostrea navicularis and Pecten cristatus (see Captain Spratt's work and papers by Lord Ducie and Dr Adams).
The prairies of south-western Louisiana have much yellow marl underlying them.