The Geologist/Volume 5/Proceedings of Geological Societies (January 1862)
PROCEEDINGS OF GEOLOGICAL SOCIETIES.
Geological Society of London.—December 4.—Sir R. I. Murchison, V.P.G.S., in the chair. The following communication was read:—"On the Bracklesham Beds of the Isle of Wight Basin." By the Rev. O. Fisher, M.A., F.G.S. After noticing the researches of Prestwich and Dixon, the author proceeded to state that most of the "Bracklesham beds" are displayed at low water at Bracklesham Bay; but other and higher beds belonging to the same series are to be observed in the New-Forest, at Stubbington, and in the Isle of Wight. By means of the fossils, for the most part, Mr. Fisher divides the series into four groups:— 1. The uppermost abounds in Gasteropoda, and has several fossil-beds. One of these, in the eastern part of its range, is full of Nummulina variolaria (No. 16 of Mr. Prestwich's Section of Whitecliff Bay, Quart. Journ. Geol. Soc. vol. ii. pl. 9); the N. variolaria bed of Selsea and of Stubbington; and the Shepherd's Gutter bed at Bramshaw, New Forest. The beds above the last-named are—1st, a portion of No. 19 of the Whitecliff Bay section and the coral-bed of Stokes Bay and Hunting Bridge (New Forest); and 2nd, the shell-bed at Hunting Bridge, and pebble-bed, with shell-casts, at Highcliff. The lowest bed of this group is the "Cypræa-bed" of Selsea, the "Cardita-bed" of Stubbington, and the Brook bed in the New Forest. 2. This group is more sandy than the last; it has two fossil-beds, one of which contains Cerithium giganteum (at Hillhead, Stubbington; and half a mile west of Thorney station, Bracklesham Bay). 3. This is a sandy group, and is remarkable for the profusion of Nummulina lævigata in its principal fossil-bearing beds. 4. This embraces the lowest fossiliferous sands of Bracklesham Bay. Its distinctive shells are Cardita acuticosta and Cypræa tuberculosa.
Some species of mollusks pass upwards from the Bracklesham into the Barton series; yet the Fauna of the Bracklesham beds has a sufficiently distinct facies; and the following species range through this series, and are confined to it—Cardita planicosta, Sanguinolaria Hollowaysii, Solen obliquus, Cytherea suberycinoides, Voluta Cithara, and Turritella sulcifera. Pecten corneus is also characteristic, but is met with higher up.
The Bracklesham beds seen at Whitecliff Bay were first treated of, and Mr. Prestwich's section referred to in detail. No. 6 (a pebble-bed) of this published section is regarded by Mr. Fisher as the base of the Bracklesham series; the upper limit being somewhere in No. 19. Descriptions followed of the beds seen at Bracklesham Bay; the eastern side of Selsea; at the Mixen Rocks; at well-sinkings near Bury Cross; at Stubbington (including the Cerithium-bed at.Hillhead, discovered by the author in 1856); Netley, Bramshaw, Brook, and Hunting Bridge (where H. Keeping has lately found a fossil-bed high in the series), in the New Forest. Indications of the western range of the marine shells of "Bracklesham" age were quoted as occurring at Lychett, near Poole, and as very rare (one Ostrea) near Corfe.
Bracklesham beds, containing marine forms, seen at Alum Bay, Isle of Wight, and at Highcliff, near Christchurch, were then described in full. The Bracklesham series is regarded by Mr. Fisher as commencing in both these sections a few feet beneath a dark-green clay (part of No. 29 of Mr. Prestwich's section of Alum Bay) containing a peculiar variety of Nummulina planulata and many shells of the Barton Fauna.
Remarks were also made on the estuarine condition of the lower Bracklesham beds in their western area; on the probable sources of their materials; on the successive deepenings of the old sea-bottom, and the formation of the pebble-beds; and lastly, on the fitness of the Bracklesham and Barton series as a field for research in the history of molluscan species.
The paper was illustrated by a series of specimens from the author's collection.
Specimens of gold in quartz-veins, of gold-dust, and of gold-ingots, from Nova Scotia, sent by Mr. Secretary Howe, were exhibited by Professor Tennant, F.G.S.