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Report of an excursion to Aylesbury, Hartwell and Stone
A. MORLEY DAVIES,
254
REPORT OF AN EXCURSION TO AYLESBURY, HARTWELL AND STONE. SATURDAY, JULY 27TH, 1912. By A. MORLEY DAVIES, D.Sc., F.G.S., Director of the Excursion. ARRIVING at Aylesbury about half-past two, the party of nineteen made their way to the famous Locke's Brick-pit at Hartwell, the classical exposure of Hartwell Clay. The director explained that this clay, not separated from the Kimmeridge Clay on the map, was probably at a higher horizon than any part of the clay of Kimmeridge cliffs, though its superposition on the Orbiculoidea latissima beds (found at Stewkley, 7t miles away) was nowhere
~
V7:"71
LL-L..d
Kimmer idge and Hartwell Cla ys .
Portland Sa nd ami
Purbeck.
~ Aptia n.
Gault .
St o lle .
FIG. 4o.-SKETCH MAP OF DISTRICT WEST OF AYLESBURY.
Scale: I inch to a mile. (From the Geological Survey Map, Sheet 46 S.W.)
actually proved. Its characteristic ammonites, of the species pallasianus and allied forms, were generally placed in the genus Olcostephanus, but some specimens he had lately found, in which the inner whorls were preserved, certainly belonged to the genus Perisphinctes. Many of the characteristic fossils were found, or purchased from the workmen, including, besides the ammonites, Astarte hartwellensis, A. soemanni, Trz;l.;onia, Perna, Protocardia,
255
EXCURSION TO AYLESBURY.
ft. in.
ft. in.
Stony cIay
Grey and greenish marls and clays with limestone bands .. ... ._. ... ...
10
0
to
It
o
o
I
0
4 9
I
7
o
0
Creamy, blue-hearted marly and shelly limestone, Natica, etc.
7
0
Hard greenish-grey gritty limestone
I
8
...
5
0
Rubbly white limestones with abundant fossils ...... ... ••• ••• ••• ...
8
0
Yellow and greenish sands with con" glomerate or Iydite-bed at base
ID
0
-
-,
l:
/'
1""-
...
Greenish yellow sands...
I' _ .!-lI
...
._. ...
\_ -
\1
I
Micaceous, sandy and glauconitic days, many f 055i15 ••• ••• ••• ••• ••• . ..
SECTION AT AYLESBURY.-H. B, some Modifications by A. M. Davies.
FIG. 4I.-GENERAL
base not seen
Woodward, 7vith
(" Memoir on Jurassic Rocks of Britain," Geol. Survey, vol. v, p. 224.)
256
A.
MORLEY DAVIES, EXCURSION TO AYLESBURY.
etc. No trace of the overlying lydite-bed could be found, except for a few pebbles in the soil. The road was then followed to the famous Bugle Pit, repeatedly visited by the Association, the last occasion however being fifteen years ago, when the late Mr. Emary acted as co-director. It is to be feared that this year's visit will be the last, as the pit is no longer worked, and is being gradually filled up with rubbish. The general succession shown in Fig. 2 was made out down to bed No.6. The most interesting feature was the well-marked "wash-out" in the Purbeck marls and limestones, filled by an unstratified clay. From the ostracods recorded from these beds the director inclined to the opinion that the unstratified clay was of Middle Purbeck age, the beds in which the hollow that it occupies is scooped out being Lower Purbeck, but the evidence is not quite clear. Mr. Whitaker said that these sections were amongst the first that he had seen on a geological excursion, when a student at University College under Prof. Morris, the others being the Charlton pit and the Grays brickyard, both now closed. At that time, about fifty-eight years ago, the sections were vertically of more extent than now. He well remembered how the learned Dr. Lee, who then lived at Hartwell House, entertained the party and distributed a large collection of fossils amongst them. On apologising to this kind host for the dirt which he carried into the house on his person, he was most courteously told" 'it is honourable dirt," an expression not to be forgotten. The Windmill Pit at Stone was next visited, where was seen the white sand of probable Aptian age, with beautiful falsebedding and occasional pebble-bands, overlain by clays and ironstone (see Plate 38). From here a good view of the vale at the foot of the Chiltern escarpment was obtained, and the principal features pointed out. After tea in the garden of the Bugle Inn, the return was made to Aylesbury by way of the" Egyptian spring," where the road-cutting gave a fair exposure of the Portland Sands, at the junction of which with the Hartwell Clay the water is thrown out. A pleasant walk through Hartwell Park completed a successful excursion, exceptionally favoured by the weather in this wet summer. Mr. Douglas Leighton was the Excursion Secretary on this occasion. REFERENCES. Geological Survey Map, t-in. scale. Sheet 46 S.W. Price 5s. 3d. Geological Survey Index Map, Old Series, Sheet 12. New Series, Sheet IS. Price as, 6d. Ordnance Survey Map, r-in, scale. Sheet 237. Price IS. r880. BLAKE, J. F.-" Portland Rocks of England." QUa1·t. yourn. Geol. Soc., vol. xxxvi, p. 189.
PROC. GEOL.
Assoc.,
VOL.
XXIII.
PLATE
38.
[Photo by T. W. Reader. SECTION SHOWING FALSE-BEDDING IN THE APTIAN SANDS, WINDMILL PIT, STONE.
To face page 256.
EXCURSION TO MOUNT SORREL AND DISTRICT.
257
1895.
WOODWARD, H. B.-" Jurassic Rocks of Britain." Mem. Geol, SUI'V., vo!. V, pp. 220-229, 278-280. 1897. DAVlRS, A. M .. AND EMARY, P.-" Excursion to Aylesbury, Hartwell and Stone." Proc, Geol. Assoc., vo!. xv, pp. 90'97. Price 6d. 1899. DAVIES, A. M.-" Contributions to the Geology of the Tharne Valley," Proc. Geo], Assoc., vo!. xvi, Price IS. 1909. - - - - - - - . - " Buckinghamshire" in Geology in the Field, Other earlier references will be found in these papers.
REPORT OF AN EXCURSION TO MOUNT SORREL, BUDDON WOOD, BRAZIL WOOD, AND DISTRICT. THURSDAY, AUGUST 29TH, 1912. By F. W. BENNETT, M.D., B.Sc., AND E. E. LOWE, B.Sc., F.L.S., Directors of the Excursion. O~ arriving at Mount Sorrel from Sileby, at 1 p.m., the party, numbering fifteen, ascended Castle Hill to take a general view of the district. Here it was pointed out that, whereas the variation in composition of the rock in and around Mount Sorrel has been frequently noted, it has not been definitely ascribed to any particular cause. The suggestion was made that it is in all probability merely a case of "differentiation in place," the acceptance of this theory carrying further interesting suggestions with it. For instance, the granite.exposed along the north-eastern edge of the mass, i.e., at Castle Hill, in the main quarry, and at Hawcliff and Cocklow Quarries, is more acid than any other found in the district. Hence the mass must be regarded as incomplete on this side if the previous existence of a completely encircling basic outer fringe be granted. This incompleteness could be accounted for by a fault parallel to the north-eastern border, of which the well-known steepness of the granite on this side may be considered suggestive. The fault would be parallel to the strike of the great dolerite dyke in the main quarry, afterwards inspected by the members. The well-known inclusions or segregation-masses in the granite of the main quarry were examined, and the evidence which has led to their being regarded as the former rather than the latter was discussed. Plate 39.A, from a photograph by Mr. D. Leighton, shows a basic dyke in the granite, and Plate 39.B, illustrating the jointing, is from a photograph by Mr. T. W. Reader. Felsite veins with chilled edges were pointed out. The Keuper Marls were seen lying undisturbed upon the
254
REPORT OF AN EXCURSION TO AYLESBURY, HARTWELL AND STONE. SATURDAY, JULY 27TH, 1912. By A. MORLEY DAVIES, D.Sc., F.G.S., Director of the Excursion. ARRIVING at Aylesbury about half-past two, the party of nineteen made their way to the famous Locke's Brick-pit at Hartwell, the classical exposure of Hartwell Clay. The director explained that this clay, not separated from the Kimmeridge Clay on the map, was probably at a higher horizon than any part of the clay of Kimmeridge cliffs, though its superposition on the Orbiculoidea latissima beds (found at Stewkley, 7t miles away) was nowhere
~
V7:"71
LL-L..d
Kimmer idge and Hartwell Cla ys .
Portland Sa nd ami
Purbeck.
~ Aptia n.
Gault .
St o lle .
FIG. 4o.-SKETCH MAP OF DISTRICT WEST OF AYLESBURY.
Scale: I inch to a mile. (From the Geological Survey Map, Sheet 46 S.W.)
actually proved. Its characteristic ammonites, of the species pallasianus and allied forms, were generally placed in the genus Olcostephanus, but some specimens he had lately found, in which the inner whorls were preserved, certainly belonged to the genus Perisphinctes. Many of the characteristic fossils were found, or purchased from the workmen, including, besides the ammonites, Astarte hartwellensis, A. soemanni, Trz;l.;onia, Perna, Protocardia,
255
EXCURSION TO AYLESBURY.
ft. in.
ft. in.
Stony cIay
Grey and greenish marls and clays with limestone bands .. ... ._. ... ...
10
0
to
It
o
o
I
0
4 9
I
7
o
0
Creamy, blue-hearted marly and shelly limestone, Natica, etc.
7
0
Hard greenish-grey gritty limestone
I
8
...
5
0
Rubbly white limestones with abundant fossils ...... ... ••• ••• ••• ...
8
0
Yellow and greenish sands with con" glomerate or Iydite-bed at base
ID
0
-
-,
l:
/'
1""-
...
Greenish yellow sands...
I' _ .!-lI
...
._. ...
\_ -
\1
I
Micaceous, sandy and glauconitic days, many f 055i15 ••• ••• ••• ••• ••• . ..
SECTION AT AYLESBURY.-H. B, some Modifications by A. M. Davies.
FIG. 4I.-GENERAL
base not seen
Woodward, 7vith
(" Memoir on Jurassic Rocks of Britain," Geol. Survey, vol. v, p. 224.)
256
A.
MORLEY DAVIES, EXCURSION TO AYLESBURY.
etc. No trace of the overlying lydite-bed could be found, except for a few pebbles in the soil. The road was then followed to the famous Bugle Pit, repeatedly visited by the Association, the last occasion however being fifteen years ago, when the late Mr. Emary acted as co-director. It is to be feared that this year's visit will be the last, as the pit is no longer worked, and is being gradually filled up with rubbish. The general succession shown in Fig. 2 was made out down to bed No.6. The most interesting feature was the well-marked "wash-out" in the Purbeck marls and limestones, filled by an unstratified clay. From the ostracods recorded from these beds the director inclined to the opinion that the unstratified clay was of Middle Purbeck age, the beds in which the hollow that it occupies is scooped out being Lower Purbeck, but the evidence is not quite clear. Mr. Whitaker said that these sections were amongst the first that he had seen on a geological excursion, when a student at University College under Prof. Morris, the others being the Charlton pit and the Grays brickyard, both now closed. At that time, about fifty-eight years ago, the sections were vertically of more extent than now. He well remembered how the learned Dr. Lee, who then lived at Hartwell House, entertained the party and distributed a large collection of fossils amongst them. On apologising to this kind host for the dirt which he carried into the house on his person, he was most courteously told" 'it is honourable dirt," an expression not to be forgotten. The Windmill Pit at Stone was next visited, where was seen the white sand of probable Aptian age, with beautiful falsebedding and occasional pebble-bands, overlain by clays and ironstone (see Plate 38). From here a good view of the vale at the foot of the Chiltern escarpment was obtained, and the principal features pointed out. After tea in the garden of the Bugle Inn, the return was made to Aylesbury by way of the" Egyptian spring," where the road-cutting gave a fair exposure of the Portland Sands, at the junction of which with the Hartwell Clay the water is thrown out. A pleasant walk through Hartwell Park completed a successful excursion, exceptionally favoured by the weather in this wet summer. Mr. Douglas Leighton was the Excursion Secretary on this occasion. REFERENCES. Geological Survey Map, t-in. scale. Sheet 46 S.W. Price 5s. 3d. Geological Survey Index Map, Old Series, Sheet 12. New Series, Sheet IS. Price as, 6d. Ordnance Survey Map, r-in, scale. Sheet 237. Price IS. r880. BLAKE, J. F.-" Portland Rocks of England." QUa1·t. yourn. Geol. Soc., vol. xxxvi, p. 189.
PROC. GEOL.
Assoc.,
VOL.
XXIII.
PLATE
38.
[Photo by T. W. Reader. SECTION SHOWING FALSE-BEDDING IN THE APTIAN SANDS, WINDMILL PIT, STONE.
To face page 256.
EXCURSION TO MOUNT SORREL AND DISTRICT.
257
1895.
WOODWARD, H. B.-" Jurassic Rocks of Britain." Mem. Geol, SUI'V., vo!. V, pp. 220-229, 278-280. 1897. DAVlRS, A. M .. AND EMARY, P.-" Excursion to Aylesbury, Hartwell and Stone." Proc, Geol. Assoc., vo!. xv, pp. 90'97. Price 6d. 1899. DAVIES, A. M.-" Contributions to the Geology of the Tharne Valley," Proc. Geo], Assoc., vo!. xvi, Price IS. 1909. - - - - - - - . - " Buckinghamshire" in Geology in the Field, Other earlier references will be found in these papers.
REPORT OF AN EXCURSION TO MOUNT SORREL, BUDDON WOOD, BRAZIL WOOD, AND DISTRICT. THURSDAY, AUGUST 29TH, 1912. By F. W. BENNETT, M.D., B.Sc., AND E. E. LOWE, B.Sc., F.L.S., Directors of the Excursion. O~ arriving at Mount Sorrel from Sileby, at 1 p.m., the party, numbering fifteen, ascended Castle Hill to take a general view of the district. Here it was pointed out that, whereas the variation in composition of the rock in and around Mount Sorrel has been frequently noted, it has not been definitely ascribed to any particular cause. The suggestion was made that it is in all probability merely a case of "differentiation in place," the acceptance of this theory carrying further interesting suggestions with it. For instance, the granite.exposed along the north-eastern edge of the mass, i.e., at Castle Hill, in the main quarry, and at Hawcliff and Cocklow Quarries, is more acid than any other found in the district. Hence the mass must be regarded as incomplete on this side if the previous existence of a completely encircling basic outer fringe be granted. This incompleteness could be accounted for by a fault parallel to the north-eastern border, of which the well-known steepness of the granite on this side may be considered suggestive. The fault would be parallel to the strike of the great dolerite dyke in the main quarry, afterwards inspected by the members. The well-known inclusions or segregation-masses in the granite of the main quarry were examined, and the evidence which has led to their being regarded as the former rather than the latter was discussed. Plate 39.A, from a photograph by Mr. D. Leighton, shows a basic dyke in the granite, and Plate 39.B, illustrating the jointing, is from a photograph by Mr. T. W. Reader. Felsite veins with chilled edges were pointed out. The Keuper Marls were seen lying undisturbed upon the