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Field meeting at Eastbourne
FIELD
MEETING
AT
EASTBOURNE.
10th July, 1937. Report by A.
J.
BULL,
Ph.D., M.Sc., F.G.S.
A PARTY of 23 members and friends proceeded from
Eastbourne Station up the East Dean Road past an old pit in lata Chalk to an exposure along a footpath behind the golf house. Here a map of the outcrops of the zones of the chalk in the district was exhibited and discussed. Specimens of Micraster and Echinocorys were shown which indicated that the Chalk was in the zone of M. cortestHdinariHm. A chart was exhibited which showed the shape variations of Echinocorys sCHtatHs from the zone of planHs up to m1tcronata, and it was demonstrated that the specimens found in this exposure fitted the appropriate zonal shape. The chart had been constructed from a large number of measurements made on zoned specimens by Mr. F. Gossling. This work was described to the Association some years ago, but has not so far been published. After specimens had been collected, the walk up East Dean Road was resumed, and the base of the M. coranguinum zone (as defined by A. W. Rowe for the coast section) was indicated in the road section. Rowe's corangHinum tabular band [11* and some pipes of Tertiary material in the Chalk were also seen. At the crest of the escarpment the party turned to the left and walked the two miles to Beachy Head. On the way some good views were obtained of the large coombes behind Eastbourne. The opinion was put forward that they had been formed under cold conditions, and were due to the same causes as the mountain cirques of the present day [2J which are occupied by snow. After tea at Beachy Head Hotel the party descended the steep path to Cow Gap where the passage from the Upper Greensand through the Chloritic Marl, here 4 feet thick, was well seen. The fossils in the Chloritic Marl are fairly well preserved and sponges, ammonites, etc. were collected. A walk of a quarter of a mile along the beach brought the party to Head Ledge which consists of Upper Greensand, and from this there is a fine view of the chalk cliffs of the headland. The cliffs are now much obscured by falls of chalk, and the detail cannot be so well seen as it was when last visited by the Association in 1925, but the westerly dip was distinctly visible especially in the sHbglobosHs Chalk. Beachy Head is the north-west limb of an anticline, the axis of which, is now occupied by sea. The complementary syncline is broad and shallow. Evidence of this had been seen in the distance during the steep descent to the beach in the bowing out to sea of the Upper Greensand reef opposite the Grand *
For list of References see p. 329.
FIELD MEETING AT EASTBOURNE.
Parade. The synclinal axis is indefinite, but funs through Meads to about Birling Gap. A good view was obtained of the faulted beach which flanks the eastern side of Beachy Head. This has been described and mapped [3J [4J. The outcrop of the Upper Greensand is repeated at least five times. When the writer described this beach, reference was made to the possibility of the faulting being due to deep seated movements. Now, however, that the district has been mapped in detail, there can be no doubt that it is merely superficial slip faulting such as occurs at the Warren, Folkestone, and elsewhere. That this was the cause of the structure was the opinion of Dr. S. \V. Wooldridge and the late G. W. Lamplugh. The Chalk rests on the weak bed of the Gault, but unlike the Warren the dip is here inland. It is probable that the movement was initiated along joints parallel to the coast, and at each successive slip a strip of Upper Greensand was thrust scawards acquiring a steep landward dip in the process. Two of these reefs arc still continuous with the main outcrop of Head Ledge and must therefore be narrow. \Vhile the superincumbent Chalk, the weight of which caused the movement, has largeh' been removed, slips arc still in progress in the low cliffs. The part.y returned to Eastbourne by the cliff path past Holvwell. REFERENCES. I.
3·
H.OWE, A. W. 1900. The Zones of the White Chalk of the English Coast, part 1. Proc. Ceol.•-1ssoc., Xyj, p. 28<). BULL, A.]. 1936. Studies in the Geomorphologv of the South Downs. Proc. Ceol. Assoc., xlyii, p. 99. . 1{EID, CLEMENT. 18'18. The Geology of Eastbournc. J-felll. Geo!. Sur.
BULL, A. ]. and ;\IILNEH, H. B. bourne-Hastings Coastline.
1925. ProG.
The Geology of the EastCeol. A 5S0C., xxxvi, p. 291.
MEETING
AT
EASTBOURNE.
10th July, 1937. Report by A.
J.
BULL,
Ph.D., M.Sc., F.G.S.
A PARTY of 23 members and friends proceeded from
Eastbourne Station up the East Dean Road past an old pit in lata Chalk to an exposure along a footpath behind the golf house. Here a map of the outcrops of the zones of the chalk in the district was exhibited and discussed. Specimens of Micraster and Echinocorys were shown which indicated that the Chalk was in the zone of M. cortestHdinariHm. A chart was exhibited which showed the shape variations of Echinocorys sCHtatHs from the zone of planHs up to m1tcronata, and it was demonstrated that the specimens found in this exposure fitted the appropriate zonal shape. The chart had been constructed from a large number of measurements made on zoned specimens by Mr. F. Gossling. This work was described to the Association some years ago, but has not so far been published. After specimens had been collected, the walk up East Dean Road was resumed, and the base of the M. coranguinum zone (as defined by A. W. Rowe for the coast section) was indicated in the road section. Rowe's corangHinum tabular band [11* and some pipes of Tertiary material in the Chalk were also seen. At the crest of the escarpment the party turned to the left and walked the two miles to Beachy Head. On the way some good views were obtained of the large coombes behind Eastbourne. The opinion was put forward that they had been formed under cold conditions, and were due to the same causes as the mountain cirques of the present day [2J which are occupied by snow. After tea at Beachy Head Hotel the party descended the steep path to Cow Gap where the passage from the Upper Greensand through the Chloritic Marl, here 4 feet thick, was well seen. The fossils in the Chloritic Marl are fairly well preserved and sponges, ammonites, etc. were collected. A walk of a quarter of a mile along the beach brought the party to Head Ledge which consists of Upper Greensand, and from this there is a fine view of the chalk cliffs of the headland. The cliffs are now much obscured by falls of chalk, and the detail cannot be so well seen as it was when last visited by the Association in 1925, but the westerly dip was distinctly visible especially in the sHbglobosHs Chalk. Beachy Head is the north-west limb of an anticline, the axis of which, is now occupied by sea. The complementary syncline is broad and shallow. Evidence of this had been seen in the distance during the steep descent to the beach in the bowing out to sea of the Upper Greensand reef opposite the Grand *
For list of References see p. 329.
FIELD MEETING AT EASTBOURNE.
Parade. The synclinal axis is indefinite, but funs through Meads to about Birling Gap. A good view was obtained of the faulted beach which flanks the eastern side of Beachy Head. This has been described and mapped [3J [4J. The outcrop of the Upper Greensand is repeated at least five times. When the writer described this beach, reference was made to the possibility of the faulting being due to deep seated movements. Now, however, that the district has been mapped in detail, there can be no doubt that it is merely superficial slip faulting such as occurs at the Warren, Folkestone, and elsewhere. That this was the cause of the structure was the opinion of Dr. S. \V. Wooldridge and the late G. W. Lamplugh. The Chalk rests on the weak bed of the Gault, but unlike the Warren the dip is here inland. It is probable that the movement was initiated along joints parallel to the coast, and at each successive slip a strip of Upper Greensand was thrust scawards acquiring a steep landward dip in the process. Two of these reefs arc still continuous with the main outcrop of Head Ledge and must therefore be narrow. \Vhile the superincumbent Chalk, the weight of which caused the movement, has largeh' been removed, slips arc still in progress in the low cliffs. The part.y returned to Eastbourne by the cliff path past Holvwell. REFERENCES. I.
3·
H.OWE, A. W. 1900. The Zones of the White Chalk of the English Coast, part 1. Proc. Ceol.•-1ssoc., Xyj, p. 28<). BULL, A.]. 1936. Studies in the Geomorphologv of the South Downs. Proc. Ceol. Assoc., xlyii, p. 99. . 1{EID, CLEMENT. 18'18. The Geology of Eastbournc. J-felll. Geo!. Sur.
BULL, A. ]. and ;\IILNEH, H. B. bourne-Hastings Coastline.
1925. ProG.
The Geology of the EastCeol. A 5S0C., xxxvi, p. 291.