The Toarcian of Bredon Hill, and a Comparison with Deposits elsewhere

Abstract

I. Geology. The Upper Lias (G 3) of Bredon Hill is shown on the Geological-Survey map as more than 300 feet in thickness. It is said to be as much as 380 feet thick, whereas at Wotton-under-Edge, some 36 miles to the south, it is said to be only 10 feet. But at the former locality the Inferior Oolite (G 5) is represented as resting directly on the Upper Lias (G 3); at the latter locality there is shown, between Inferior Oolite and Upper Lias, a development of some 150 feet of strata called ‘Midford Sand’ (G 4)—the Cotteswold Sands overlain by the Cephalopod-Bed. The question often presented itself to my mind—Were the two so-called ‘series’ of Upper Lias the same, or was not the Upper Lias of Bredon Hill really much more than the Upper Lias of Wotton, so that there was not a true comparison? Was it not an argillaceous condition of the sands and the overlying Cephalopod-Bed? Some few years ago I was able to answer this question partly in the affirmative. On the north slope of Bredon Hill, I found in some argillaceous stones in a gateway, many feet below the yellow limestone of the Inferior Oolite, portions of ammonites indicative of beds contemporaneous with the Cephalopod-Bed of the Cotteswolds: they indicated strata of the hemerae Moorei, dispansi , and Struckmanni . When the Cotteswold Naturalists9 Field-Club visited Overbury on the south side of Bredon Hill, in 1902, the members found in the gravel-pit many ammonites confirming my