Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/113

Rh LATER TERTIARY GEOLOGY OF E^ST AKGLIA. 75 times twenty feet thick, did they present any traces of the Chilles- ford Clay over them." In some of the excavations for the extraction of phosphatic nodules (coprolites) these sands seem to pass down into the Red Crag by thin seams of comminuted shell ; but in others they present an appearance which, in the case of other formations, would be regarded as clearly indicative of unconformity ; for their stratification is wholly indepen- dent of the shelly crag beneath them, while the sands themselves often overlap and envelop the latter. In some instances (but these are the exception) they present the same oblique stratification which is possessed by the greater part of the shelly beds of the Red Crag. In others, such as that shown in section III. (page 81), detached and apparently disconnected portions of the shelly crag are imbedded in these sands, just as though they were transported masses imbedded while the sands were being accumulated. Fig. 1. — Section I., in a Coprolite-pit one mile and a half north- west of Waldr'uiQ 'field church. (Scale 10 feet to the inch.) a. Eed Crag, unaltered and full of shells. b. Red stratified sands, being a altered and restratified. c. Pipe filled with sand traversing both the altered and unaltered Crag. The above section (I.) represents the usual way in which these sands overlie the shelly crag, so far as their stratification is con- cerned ; but in that section another stratification occurs in a band of pebbles which, while conformable to that of the shelly crag where it is included in that material, cuts obliquely across the horizontal stratification of the unfossiliferous sands. It has long been known, and it is mentioned by Mr. Prestwich in his paper on the Eed Crag *, that these sands occasionally include ironstone casts of Crag shells. These we have found loose in them. Mr. Whi taker also, about two years ago, discovered in a pit three quarters of a mile N.E. of Kesgrave church, some bands of ironstone in these unfossiliferous sands which contained numerous and well- preserved impressions of Red -Crag shells, to which he called the attention of one of us, expressing his opinion that the sands in which these bands of ironstone occur had once been fossiliferous like the shelly crag, but had been deprived of their shells by the action of acidulated waters. The difficulties in the way of that view appeared to us to be, that the line dividing the shelly crag from these sands was abrupt, no
 * 1) . Seam of flint-pebbles.
 * Quart. Journ. Geol. Soc. vol. xxvii. p. 330.