August 31, 1882] 



NA TURE 



433 



to either Colwell Bay, or Headon Hill and Brockenhurst, and 

 not occurring at Barton; while there are twenty-six ' species 

 rommon to Colwell Bay and Headon Hill, and not occurring at 

 brockenhurst. It is clear, therefore, from all fossil and physical 

 >r slratigraphical evidence, that ihe position of the Brockenhurst 

 bed has been misconceived, and it would be fatal to re-name the 

 whole series of strata hitherto so well known and well deter- 

 mined as the Middle Marine or Middle Headon of the Isle of 

 Wight, aid call it the "Brockenhurst series." The classifica- 

 lion and nomenclature of the Geological Survey must therefore 

 be restored and maintained, all recent examination having 

 strengthened the previous labours of Forbes and Bristow, and 

 ihe later re- earches of Messrs. Tawney and Keeping, have still 

 more firmly established the succession and correlation of the 

 Middle Headon series of the bland, and affording a basis for 

 further research and analysis for the "Anglo-Parisian or Hamp- 

 shire Tertiary Basin." 



Mr. Tawney prepared an important paper upon the Upper 

 Bagshot Sands of Hordwell Cliff, which was read before the 

 Cambridge Philosophical Society, and published in their Pro- 

 ceedings. The object of the communication was to discuss the 

 affinities of ihe Bagshot series with a view to their classification, 

 and also to endeavour to show their correlation and equivalents 

 in the Paris basin. "All observers are agreed as to the actual 

 position of the sands being below the fresh-water Lower Headon. 

 Edward Forbes and the Geological Survey distinctly ally it to 

 the Marine Bagshot beds. They place it in the Middle Eocene 

 Bagshot series, terming it Upper Bagshot {instead of Headon 

 Hill Sands). Forbes noticed its containing Barton species at 

 Wliitecliff Bay. This leads to or shows its affinity to Uarton 

 beds. Dumont favoured a similar classification in his essay, and 

 in his table the Headon Hill sands are grouped with the Barton 

 clay as being respectively equivalent to the upper and Lower 

 divisions of the Belgian J.aekenian, while the Headon Hill 

 limestones and marls are ] laced 'longrien. Lately these views 

 have been questioned by the author ot the " Oligocene Strata of 

 the Hampshire Basin," in ihe Quarterly Journal of the Geo- 

 logical Socuty, vol. xxxvi., who regards them as constituting the 

 lowest member of the Headon group, stress being laid upon the 

 occurrence of Cerithium eoncavum as a test. The author also 

 places the whole of the I'pper Bagshot sands and the Lower 

 Middle Headon beds as the equivalents of the Mortefontaine 

 sands, placing them above the St. C'uen limestone ; these St. 

 Ouen beds representing perhaps the Osborne, and all three 

 Headon divisions, which come above the Mortefontaine beds. 

 Ceiithium eoncavum is said to occur both in the Bagshot and 

 Headon series. Careful research and examination shows that 

 the shell in question is Lamarck's C. pleurotomoides in the one 

 case, and not C. eoncavum, which species has evidently been 

 confounded with tie Lamarck ean shell. Examination of equi- 

 valent beds in France by Mr. Tawney, and the researches of 

 Prof. Herert and M. Murier-Chalmas clearly show that ihe 

 Mortefontaine sands do not contain Cerithium eoncavum, the 

 shell so common on that horizon being C. pleurotomoides 1 amk." 

 Comparison of the Headon shell with iho-e brought from near 

 Mortefontaine shows that the Long Mead End species agrees 

 with the French form. It would appear that there is much 

 greater parallelism between the French and English series than 

 we have hitherto expected. The Mortefontaine sands are the 

 upper part of the Sables de Beauchamp, representing our 

 Barton beds ; above this comes the Calcaire de St. Ouen, chiefly 

 of freshwater origin. Connected with the St. Ouen limestone 

 are sands and marls, containing at the top and bottom Cerithium 

 eoncavum abundanily. 



The St Ouen period, therefore, without doubt represents our 

 Headon series. " In our Hampshire basin the freshwater and 

 marine condition in the Headon series are not in the same order 

 as in the St. Ouen beds." "The marine fades in Hampshire, 

 with C. ectuavum, comes between the freshwater Lower and 

 Upper Lleadon deposits, near Montjavoult ; the bulk of the 

 freshwater limestone is in the centre or between two deposits with 

 this Cerithium eoncavum'' "In the Paris basin, therefore, the 

 zone of C. eoncavum is not connected with the zone of C. pleuroto- 

 moides, but comes immediately above it." Thus C. eoncavum 

 characterises the Middle Headon of Colwell Bay and Hordwell, 

 while C. pleurotomoides is found o:Jy in the Upper Bagshot of 

 Long Mead End. That the Long Mead End sands, and those 

 of Mortefontaine are equivalents few can doubt. Both succeed 

 or constitute the uppermost portion of the Barton beds, and 25 

 per cent, of the fossils are in common. These affinities show 



that the term Upper Bagshot sands is the most appropriate, and 

 expresses the relationship of these sands, since the Barton and 

 Bracklesham beds together are usually considered as the equi- 

 valents of the Middle Bagshots. The author believes, therefore, 

 that it would be wrong to reject Edward Forbes's name of 

 " Upper Bagshot" for the Long Mead End sands, and accept in 

 place of it the older term of Headon Hill sands. 



Mr. A. H. S. Lucas, M.A., in his concise but valuable paper 

 "On the Headon Beds of the Western Extremity of the Isle of 

 Wight" (Geological Magazine, n.s. decade ii. vol. ix.), correctly 

 states, upon referring to the recent " answer to the present 

 questioning of the hitherto accepted correlations of the beds of 

 the Lower fluvio-marine Tertiaries of the Isle of Wight and 

 South Hants, that it is obviously impossible for foreign geo- 

 logists to institute useful comparisons between British and foreign 

 subdivisions so long as we in England are quite at variance on 

 the stiatigraphical and pala:ontological facts of the beds in 

 question. 1 



"The general relation of the whole group can only be satis- 

 factorily determined after the primary question of the continuity 

 or discontinuity of the Colwell Bay and Lleadon Hill beds is 

 settled. At present there are two very definite, yet different 

 views, having a perfectly distinct issue ; first, that the brackish- 

 marine beds of Colioell Bay coy respond to the braekieh-manue beds 

 of Headon Hill which have been seen ; or, secondly, that they 

 correspond to some higher marine beds which have not been seen." 

 Both ihese views a> d arguments are now fairly before those 

 competent to judge. In 1SS0, however, Prof. Judd, in his paper 

 "On the Oligocene Strata of the Hampshire Basin" (Quarterly 

 Journal of the Geological Society, vol. xxxvi., p. 137, &c. ), 

 questioned and denied the succession as determined by Forbes 

 and the Survey ; this paper dealt with strata or higher marine 

 beds, stated above by Mr, Lucas as " not having been seen." On 

 the other hand, in 1S81, Messrs. Tawney and Keeping brought 

 to bear upon the question a mass of evidence in support of the work 

 of Edward Forbes and the Survey (Quarterly Journal of the 

 Geological Society, vol. xxxvii. p. S5), showing conclusively the 

 identity and continuity of the Colwell Bay and Lleadon Hill 

 fluvio-marine beds. Still more recently, however, Prof. Blake 

 (Proceedings of the Geological Association, vol. vii.) has " ad- 

 vanced an entirely new correlation, adducing stratigraphical 

 evidence in its favour." His observations do not agree in 

 certain cases either with tho-e of Prof. Judd or Messrs. Tawney 

 and Keeping. It is hoped, however, by or through evidence at 

 the present meeting, that the questh n of the succession will be 

 finally determined. Mr. Lucas does not attempt any solution as 

 to the relation of these beds at Colwell Bay and Headon 

 Hill to the deposits exposed at Hordwell, Brockenhurst, or 

 Whitecliff Bay ; they do not concern the succession. But the 

 standard or synthetic sections at different localities, like those 

 prepared by Messrs. Tawney and Keeping, have tended to clear 

 up the succession, fully testing the continuity of these beds under 

 di-pute under their several aspects along the plane of deposition. 

 This independent m >de fully bears out the exact work of the 

 Survev, showing differences in degree as regards accumulation, 

 yet continuity as regards succession. Mr. Lucas gives measured 

 sections of the freshwater beds, and the brackish marine series 

 (p 99 loe. eit.), which confirm the work of the above authors. 



The Headon beds were long ago "measured by Dr. Wright, 

 lately by the authors just quoted, and the Osboine series by 

 Edw ard Forbes, and the main divisions are so conspicuous that 

 there can he no doubt about the succession." A third paper 

 upon the fluvio-marine beds of the Isle of Wight was read 

 before the Geologists' Association in June 1SS1, under the title, 

 "On a Continuous Section of Oligocene Strata from Colwell 

 Bay to Headon Hill " (Proceedings of the Geological Associa- 

 tion, vol. vii.), by Prof. J. F. Blake, M.A., F.G.S. The 

 author contends for a difference between the fauna; of the 

 Colwell Bay beds and those of /laden Hill, and states that the 

 " fauna of the so-called Oligocene group is chiefly to be found 

 in the 'Venus bed" of Colwell Bay; but the assumed other 

 ' Venus bed ' at Headon Hill contains rather the fauna of the 

 uppermost Eocene, or zone of Cerithium eoncavum." The 

 question, however, turns upon the identity of the two so-called 

 Venus beds. In other words, the Colwell Bay "Venus bed" 

 1 A concise and important paper on "The Classification of the Tertiary 

 Deposits." by Prof, Judd, appeared in the Popular Science Rcz'iev' .or 

 1880, accompanied by a table showing the correlation of the Lower Tertiary 

 strata of Western Europe. The Headon and Brockenhurst beds are placed 

 under the Lower Oligocene, and the Eembridge and Hempstead series under 

 the Middle Oligocene. 



