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Excursion to Tilburstow Hill
EXCURSION TO TILBURSTOW HILL.
From Writtle Wick the party made its way to Chelmsford Railway Station, time not permitting a visit to the pits in Glacial Gravel, at Writtle, or to the Brickearth sections in which the jaw of the Mammoth was discovered last year. The Director has pleasure in acknowledging the services rendered by Mr. W. Cole, Hon. Sec. Essex Field Club, and by Mr. H. Mothcrsole, for information respecting the sections of the district, etc. REFERENCES. Geological Survey Map, Sheet ISS'). IS'!/,
I,
N.E. (Drift Edition).
or
\YHITAKER, \V.-" The Geology London," etc . .VOIt. Ceo!. SU)'1·/:1'. i\!O:
vol. x ii.
EXCURSION TO TILBURSTOW HILL. SATURDAY, 15Tl-i JUNE, 1895. Director: THOS. LEIGHTOK, F.G.S. (Report by THE DIRECTOR.)
THE object of this excursion was to examine the geology of the eastern portion of the district recently described by the director in a paper read before the Geological Society." In this paper the author stated that he had been unable to place the sections exposed at the north of the Tilburstow Hill district in the succession of beds made out a few miles to the west, whilst in the programme issued for this excursion, t it was further stated that the director had now an opinion to offer on the subject. Full details of the various sections visited on this occasion in the neighbourhood of Tilburstow Hill, will be found in the paper referred to above, published by the Geological Society. The director stated that he had now arrived at the conclusion, both upon stratigraphical and lithological evidence, that the beds exposed in the three large pits of the Tilburstow Hill Plantation (north of the high road), were approximately on the horizon of Meyer's Folkestone Stone-Beds of the Redhill district (i.e., " Stone-Beds and Fullers' Earth" of Fig. 4 of the table appended to the author's paper already referred to.) In the Redhill district, the Geological Survey places these beds in its" Sandgate" division, but in the neighbourhood of Tilburstow H ill Plantation, the official information of both map and memoir is too meagre for identification. The present writer's Local Group No. I, has the beds in question for its upper members in both districts. Strat(r;rafltiml Evidence.- The level and dip of the massive chert beds exposed behind Rabbitsbcath Cottages are not incompatible with their passage under the beds exposed in the three pits to the north. The Fullers' Earth has been admitted by * Quart./ourn. Geol. Soc., \'01. li , 1895. t Circular, dated 17th May, 1895.
NOVEMBER, 1895.J
19 2
EXCURSION TO T1LBURSTOW H [LL.
all geologists to lie in basins, not mathematically on the same horizon, but always about the same horizon; hence the presence of Fullers' Earth above the massive cherts of the "Fault Pit," near the Roman Road, may be of no stratigraphical importance. Likewise, the presence of thick Fullers' Earth above the calcareous beds in the Plantation Pits, whilst at Nutfield the thick Fullers' Earth lies below similar beds. cannot be taken as an argument against the two series of beds (Fullers' Earth and" associated rocks") lying on the same horizon. Lithological Evidence. -The correct horizon of the beds of the Plantation Pits becomes clearer. however, when the nature of the rocks associated with the Fullers' Earth, exclusive of the blue stone, is examined. The beds described by the present writer as "Calcareous clayey greensand "* will be found to bear a strong family likeness to the twenty-six feet of "Stonebeds" at Nutfield, mentioned on page 1I4 of the same paper, wllilst similar beds are found nowhere else in this part of the series, certainly not in any part of the underlying chert beds. It has also to be remembered that both at Nutfield and Tilburstow Hill the iron-sands of the Folkestone Beds follow upon the series under discussion. Dr. G. J. Hinde stated that he believed the chert of the Plantation Pits, described by the director as "blue stone," to be the same as that seen behind Rabbitsheath Cottages and in the" Fault Pit" near the Roman Road. the difference in the chert seen in the first and two other exposures being due to weathering. The director stated that he had, following Dr. Hinde, t favoured that view when writing his paper, there were some stratigraphical points which supported it. However, he considered that the absence of wbat he had described as the "associated rocks" from the two last-named exposures, rendered his present explanation, viz., that the Plantation Pits displayed a slightly higher horizon, the more acceptable. It should he noticed that should the view favoured by Dr. Hinde eventually turn out to be the correct one, the writer's present explanation of the succession of beds at Tilburstow Hill will remain unaltered, but the thickness of the cherty series will be slightly reduced. REFERENCES. Geolorrirnl Survey Map, Sheets 6 and 8 (Drift Edition). New Ordnance Survey Map. Sheet 286. Six-Inch Ordnance Survey Map, Surrey, Sheets 27 and 35.
1866.
r875. 1895.
ME\'ER, C. J. A.-" Noles on the Correlation of the Cretaceous Rocks of the South East and West of England." CeDI. lvIa.t::. vol. iii. TOPLEY, W.-" Geology of the Weald." lvIem. Ceo!. Survey. LEIGHTON, T.-" The Lower Greensand . . . of East Surrey." Quart. Journal Ceo!. Soc., vol. Ii. * OJ. cit., p, 117. t J>hil. 1 rans., r88s.
From Writtle Wick the party made its way to Chelmsford Railway Station, time not permitting a visit to the pits in Glacial Gravel, at Writtle, or to the Brickearth sections in which the jaw of the Mammoth was discovered last year. The Director has pleasure in acknowledging the services rendered by Mr. W. Cole, Hon. Sec. Essex Field Club, and by Mr. H. Mothcrsole, for information respecting the sections of the district, etc. REFERENCES. Geological Survey Map, Sheet ISS'). IS'!/,
I,
N.E. (Drift Edition).
or
\YHITAKER, \V.-" The Geology London," etc . .VOIt. Ceo!. SU)'1·/:1'. i\!O:
vol. x ii.
EXCURSION TO TILBURSTOW HILL. SATURDAY, 15Tl-i JUNE, 1895. Director: THOS. LEIGHTOK, F.G.S. (Report by THE DIRECTOR.)
THE object of this excursion was to examine the geology of the eastern portion of the district recently described by the director in a paper read before the Geological Society." In this paper the author stated that he had been unable to place the sections exposed at the north of the Tilburstow Hill district in the succession of beds made out a few miles to the west, whilst in the programme issued for this excursion, t it was further stated that the director had now an opinion to offer on the subject. Full details of the various sections visited on this occasion in the neighbourhood of Tilburstow Hill, will be found in the paper referred to above, published by the Geological Society. The director stated that he had now arrived at the conclusion, both upon stratigraphical and lithological evidence, that the beds exposed in the three large pits of the Tilburstow Hill Plantation (north of the high road), were approximately on the horizon of Meyer's Folkestone Stone-Beds of the Redhill district (i.e., " Stone-Beds and Fullers' Earth" of Fig. 4 of the table appended to the author's paper already referred to.) In the Redhill district, the Geological Survey places these beds in its" Sandgate" division, but in the neighbourhood of Tilburstow H ill Plantation, the official information of both map and memoir is too meagre for identification. The present writer's Local Group No. I, has the beds in question for its upper members in both districts. Strat(r;rafltiml Evidence.- The level and dip of the massive chert beds exposed behind Rabbitsbcath Cottages are not incompatible with their passage under the beds exposed in the three pits to the north. The Fullers' Earth has been admitted by * Quart./ourn. Geol. Soc., \'01. li , 1895. t Circular, dated 17th May, 1895.
NOVEMBER, 1895.J
19 2
EXCURSION TO T1LBURSTOW H [LL.
all geologists to lie in basins, not mathematically on the same horizon, but always about the same horizon; hence the presence of Fullers' Earth above the massive cherts of the "Fault Pit," near the Roman Road, may be of no stratigraphical importance. Likewise, the presence of thick Fullers' Earth above the calcareous beds in the Plantation Pits, whilst at Nutfield the thick Fullers' Earth lies below similar beds. cannot be taken as an argument against the two series of beds (Fullers' Earth and" associated rocks") lying on the same horizon. Lithological Evidence. -The correct horizon of the beds of the Plantation Pits becomes clearer. however, when the nature of the rocks associated with the Fullers' Earth, exclusive of the blue stone, is examined. The beds described by the present writer as "Calcareous clayey greensand "* will be found to bear a strong family likeness to the twenty-six feet of "Stonebeds" at Nutfield, mentioned on page 1I4 of the same paper, wllilst similar beds are found nowhere else in this part of the series, certainly not in any part of the underlying chert beds. It has also to be remembered that both at Nutfield and Tilburstow Hill the iron-sands of the Folkestone Beds follow upon the series under discussion. Dr. G. J. Hinde stated that he believed the chert of the Plantation Pits, described by the director as "blue stone," to be the same as that seen behind Rabbitsheath Cottages and in the" Fault Pit" near the Roman Road. the difference in the chert seen in the first and two other exposures being due to weathering. The director stated that he had, following Dr. Hinde, t favoured that view when writing his paper, there were some stratigraphical points which supported it. However, he considered that the absence of wbat he had described as the "associated rocks" from the two last-named exposures, rendered his present explanation, viz., that the Plantation Pits displayed a slightly higher horizon, the more acceptable. It should he noticed that should the view favoured by Dr. Hinde eventually turn out to be the correct one, the writer's present explanation of the succession of beds at Tilburstow Hill will remain unaltered, but the thickness of the cherty series will be slightly reduced. REFERENCES. Geolorrirnl Survey Map, Sheets 6 and 8 (Drift Edition). New Ordnance Survey Map. Sheet 286. Six-Inch Ordnance Survey Map, Surrey, Sheets 27 and 35.
1866.
r875. 1895.
ME\'ER, C. J. A.-" Noles on the Correlation of the Cretaceous Rocks of the South East and West of England." CeDI. lvIa.t::. vol. iii. TOPLEY, W.-" Geology of the Weald." lvIem. Ceo!. Survey. LEIGHTON, T.-" The Lower Greensand . . . of East Surrey." Quart. Journal Ceo!. Soc., vol. Ii. * OJ. cit., p, 117. t J>hil. 1 rans., r88s.