On the Structure of the Crag-beds of Suffolk and Norfolk, with some Observations on their Organic Remains

Abstract

Conclusion In the former part of this paper, I remarked that the Coralline Crag had, during its latter stages, been subject to a process of slow elevation, but probably without rising above the sea-level. It had, however, emerged above the sea at the commencement of the Red-Crag period, as evinced by the shore-line at the base of the Red Crag at Sutton (see Pl. VI.), when the Coralline-Crag reef or islet stood some 40 feet or more above that shore-line. The difference of level between the lower shore-line and the surface of the London Clay under the Red Crag in the adjacent district is not more than a few feet, whence the Red Crag must have been accumulated in a shallow sea. Mr. Searles Wood, Jun., considers that the lower division of the Red Crag is arranged in successive beach-stages. There seems to me, on the contrary, to be an absence of definite order; and the lamination and bedding which he considers referable to beach-action, I think may in all cases be referred to the variable bedding and oblique lamination produced by the shifting of shoals and sand-banks at the bottom of the Red-Crag sea, as was the case with the upper division of the Coralline Crag ( ante , fig. 3, p. 120). Mr. Wood, Sen., has already expressed his opinion that the peculiar stratification of the Red Crag must b e owing to the constant shifting of the sands and shingle caused by variable and changing currents ; and this