1911 Encyclopædia Britannica/Bone Bed
BONE BED, a term loosely used by geologists when speaking generally of any stratum or deposit which contains bones of whatever kind. It is also applied to those brecciated and stalagmitic deposits on the floor of caves, which frequently contain osseous remains. In a more restricted sense it is used to connote certain thin layers of bony fragments, which occur upon well-defined geological horizons. One of the best-known of these is the Ludlow Bone Bed, which is found at the base of the Downton Sandstone in the Upper Ludlow series. At Ludlow itself, two such beds are actually known, separated by about 14 ft. of strata. Although quite thin, the Ludlow Bone Bed can be followed from that town into Gloucestershire for a distance of 45 m. It is almost made up of fragments of spines, teeth and scales of ganoid fish. Another well-known bed, formerly known as the “Bristol” or “Lias” Bone Bed, exists in the form of several thin layers of micaceous sandstone, with the remains of fish and saurians, which occur in the Rhaetic Black Paper Shales that lie above the Keuper marls in the south-west of England. It is noteworthy that a similar bone bed has been traced on the same geological horizon in Brunswick, Hanover and Franconia. A bone bed has also been observed at the base of the Carboniferous limestone series in certain parts of the south-west of England.