Monday, May 31, 2010
Nautiloid shell calculations
Since the view of the middle whorl of the Cimomia shell from Kingsley Wood was tangential the breadth of 63 mm measured near the umbilicus is about five chambers and a quarter whorl beyond the smaller septum seen to have edges in the median plane of symmetry 21 and 45 mm from the axis of coiling. The whorl expansion rate W = 45/21 in 360° when converted to a natural logarithm and multiplied by 0.25, and then used as an exponent of e = 2.17 etc. will predict the subsequent increase in breadth and therefore the likely true breadth of the hidden small septum (i.e. it is 63/1.21 – 52 mm). By the same calculation, but going backwards for half a whorl, the radius 45 mm is reduced to 31 mm. The shell diameter is then 45+31 = 76 mm where the breath is 52 mm and the median height 45-21 = 24 mm. One can, however, see that the next whorl expands less and this can be measured as W = 97/63 more reliably than on the partly missing venter (r= 68 mm or more). Using the lower rate the breadth corresponding to a diameter of 76 mm becomes 56 mm or about 74%. Using these revised measurements the shell looks a more normal shape, but still develops a depressed and slowly expanding outer whorl with a more semicircular cross-section. The following museum specimens of Cimomia imperialis are of that variety, if clearly mature with more closely spaced final septa, with relatively pyrite-free calcite rim cements for probably Highgate material. The mature shell of 82.3 mm diameter and 57 mm breadth is labelled Highgate IPM B2155g in the Paris Nat. Hist. Mus. The only specimen, which I saw in Saffron Walden Museum, is almost certainly the one from G.S. Gibson (1818-1883) listed as “Nautilus centralis from Eocene Higate”. It showed a breadth of 59 mm at 65.5 mm. Oxford University Museum specimen 595/2 had no locality but was an old donation with measurement 63 mm at 80 mm. Other specimens from the pyrite-filled variety of Highgate septaria and Essex division E sites on the M11 and M25 are considerably larger, and become more not less compressed on the outer whorl.
Kingsley Wood Fossils Rayleigh
On April 6, 2010, I visited the cutting of the London Clay Formation near Kingsley Wood in Rayleigh on the Southend Arterial road (A127) for the first time as a pedestrian. My first memories of the site were provided by the moving ‘city coach’ from Grove Road in Woodford to Southend in the summer of 1953. Since I seldom went that way since and the novelity of the scene declined, the visual images must date from then. Looking from the north side of the coach, there was a succession of wooden posts supporting power lines beside the cycle track in the plain, which gave way to woods and a curved ascent below a bare slope with yellow sands at the top. Looking the other way, with more difficulty, the traffic returning from Southend was to be seen down below beside woods.
On July 7, 1966, on a school coach ride from Southend to Portsmouth armed with the British Geological Survey 10 miles to the inch map of England, I made the following initial comments in my notebook: “Eastwood London Clay, Progress Road,….Rayleigh Weir, Bagshot sands, farmland arable.’’
Before 1922, the Ordnance Survey mapped a lane rising from 144 feet O.D. (44 m) at a bend in the western plain mapped previously by B.G.S. at the base of the Bagshot Beds, past 164.6 feet (50 m O.D.) at the lowest corner of Kingsley Wood, where later B.G.S. maps mark the base of the revised boundary termed lower Claygate Beds (Bristow et al. 1980), to an eastern summit height of 228 feet (69 m) on the only part of this lane which now exists. It is now a footpath between the west end of Kingsley Avenue and the eastern end of the south cutting made in 1922-3.
It must have been here, where there is a modern O.S. spot height in the A127 road surface 60.4 m O.D., 110 m N.W. of the end of the cutting at the truncated lane, that Eocene fossils were dug up by spadework in 1922-3. The present south cutting, now mature woodland with soil cover, was made then by loading the clay directly on to narrow gauge railway waggons, transporting it along what is now the south cycle track to an embankment in the western marshy plain. According to the resident road engineer, Mr. Thomson, “all the fossils come from one thin bed which was encountered at the base of the cutting at the highest point of the road (200 ft. O.D.)” (Wooldridge & Berdinner 1925). This is not literally the highest point, which was at around 230 feet beyond the cutting where the unweathered partly pyritic and largely uncemented marine aragonitic shell would not have been preserved. However, it is also not at the Grid Reference TQ 7940 8986 cited for the fossils by Bristow et al. (1980), about 150 m to the N.W. on the upper slope of the north cutting.
A photograph taken around 1930 from the end of the truncated lane shows both cutting with a thin cover of grass and denser older vegetation on a 2 m bank starting at a lane on the west end of the south cutting (photograph 108 of Lane & FitzGerald 1991). That marks an old field boundary, since removed and on my visit consisting of a small extension of the cycle track with barren brown clay and bricks dumped in it. The opposite side of the road is seen in profile on the photograph slightly nearer to the camera as a steep rise, followed by a more concave grass slope rising at about 55 m O.D. into a more gentle slope still covered with a line of dense bushes then not removed. Above them was the power lines remembered from my youth and present in 2010 on replaced poles running across a cleared corner of the enlarged 1938 cutting (from posts 13 to 15 on the edges of it). Slumped orange sands and clays are present in that corner of the cutting rising to the 70 m O.D. contour line. It was made in 1938 to add a north lane and cycle track up to 2m above the south lane of the A127 on the curved illustrated slope, removing a lower part of Kingsley Wood (not appearing to have large trees on it in photograph) and the upper line of bushes running eastwards.
My interest in visiting these cutting started on March 17, 2010 when I was shown a Cimomia imperialis (J. Sowerby) aragonite nautiloid shell, collected there in 1922 by W. H. Borke. He worked for the Rayleigh Builder J. T. Byford rather than as part of the labour force travelling from London on this Government make-work-project. The outermost septum on three half-whorls of the internally unbroken, hollow phragmocone, had an undistorted breadth of 97 mm, an incomplete venter to coiling axis radius of 68 mm. The next whorl had corresponding dimensions of 63 mm breadth half a whorl beyond a 45 mm radius showing around one of about 8 mm blocked by grey claystone. There measurements are adjusted in my entry on nautiloid shell calculations a height in the median plane of 24 mm. The third whorl with a radius of 23 mm showed the siphuncle between a tangential view of the septa. The 18 mm diameter umbilicus was open.
Doubts had previously been raised about the stratigraphy of these fossils, said to come from the Claygate Member of the London Clay Formation in current B.G.S. nomenclature based on Bristow et al. (1980). In the Hadleigh (Sand Pit Hill) B.G.S. borehole, only three km to the south, the glauconitic sands defining the base of the Claygate Member were 132 m above the base of the London Clay, with both pyrite and calcite septarian concretions in clays around 135 m, and sands with iron pan cementation defining the base of the Bagshot Formation at 149.6 m (Lake et al. 1987, p. 70-71). But according to a reliable well record, from Burches Farm in Whitaker & Thresh (1916), marked on B.G.S. 1:50,000 series sheet 258/259 0.4 km west of the Esso station at the A127 opposite Kingsley Wood, the base of the pure London Clay at –68.8 m O.D. would only be about 120 to 140 below the Claygate Member and Bagshot sands mapped there. Elsewhere in the Rayleigh Hills, Eastwood and in the Southend cliffs, I had recognized from septarian calcite marker beds that mapped correlations based on similar-looking sand layers and spring lines were not correct when they opposed the well data in this way. In central Rayleigh there were three occurrences of septaria, 1) a sandy unlaminated variety weathering yellowish orange ( 10YR 7/6) around a darker brown core in the highest levels of Rayleigh Station Carpark, 2) a fine-grained claystone with an orange (10YR 8/4) exterior, around a rather dull-looking interior (10YR 7/4 – 10YR 6/4) contrasting with thick moderate yellow brown (19YR 5/4) calcite veins and dark olive grey (5Y 3/1) jointing, at 60 Love Lane, 6 metres higher than the lowest of the carpark fins and 3) septaria of intermediate grain size, with Chondrites burrows more strongly weathered out than at Love Lane and containing Teredolites borings in wood, in a thin clay layer close to the 217 foot O.S. spot height on the Hockley Road, in the new entrance to Rosedale Court. This entrance also showed dumped bricks etc. But when the adjacent field was excavated in May, it also showed Eocene clays at 66 m O.D. The Cimomia shell was only cemented by a thin film of locally hemispherical pyrite, covered by a 5 mm of grey fine-grained and internally smooth calcite rim cement, and like benthic shells seen in November 1991 in the Essex Field Club collection at Stock Street (West Ham) did not come from any kind of large claystone concretion at Kingsley Wood. However, it did seem worthwhile looking to see if the cited altitude corresponded to these markers or other features here.
On going to the area on April 10, I found that three different temporary excavations yielded samples of interest, near but not in the A127 cuttings. The highest level of Rayleigh Carpark had again been dug up and showed parts of the septaria seen before higher up the same bank with some sands and silts, above brown clays. Probably it’s this horizon which B.G.S. takes as the base of the Claygates on the A127, perhaps with a local increase in sand thickness there. I would correlate it with unit SH-11b of King (1984) and my MacMurdo Road bed. A clay ditch (less than one m) had been dug from the fence of the A127, 40 of my paces (0.84m) N. W. from the old field boundary with the clay dumped in it at 55 of my paces from the next old field boundary defined now by the edge of the Esso Station on a nursery exit. Exactly under the fence there was a relatively fine-grained and wet clay, yielding a large fragment of a septarium of the Love Lane type matching the colour of the host brown clays when wet and inconspicuous. A decayed pyrite nodule and a smaller similar fragment of probably the same concretion were found loose in the bank disturbed by the exit of digging machine. When dried the larger fragment showed a tabular exterior surface of 2-4 mm, diameter low Chondrites coloured greyish orange (10YR 7/4) like interior matrix surfaces between the open septarian cracks of 10 mm width, showing olive grey (5Y 4/1) jointing around harder 3 mm, fine-grained smooth white calcite rim cements. When broken open the claystone matrix was locally white and more generally coloured yellowish brown (10YR 6/4), with no obvious sedimentary lamination or macrofossils. The upper parts of the ditch, extending for 170 paces, was of interest in showing none of the sand layers seen slumped down below the top of it on the opposite slope.
A third sampled exposure was for new gas mains along Rayleigh High Road and included a shallower branch also of only about one metre depth into Weir Farm Road where the surface altitude can be deduced to be at 66 m O.D. from a spot height at 67.4 m O.D. on the adjacent yellowish orange (10YR 6/6) sandy ridge where Glassey Road joins the High Road. The lower excavation showed some of these sands and iron pan; but mainly consisted of a well sorted 0.1 mm diameter quartz sand, with abundant similar-sized black and scarce green grains of less altered glauconite, giving it a homogeneous yellowish grey (5Y 7/4) colour when dry, and locally black when dug up. This lithology looked like glauconitic sands at Springwater Road in Eastwood, which has previously been mapped a few metres above the base of the Claygate Beds, rather than just under the Bagshot Beds. Later in April 2010, I attempted to level across from the septarium site on to the opposite north cutting, where both loose septaria fragments and slumped overlying sand ridges were observed. The highest and most interesting concretion was three of my nominally 1.78 m eye levels about the septaria site and 59 paces from the north cycle track, about level with the lowest ridge containing sand at the higher of two bends in the Kingsley Wood boundary fence at power line post 15, five eye-levels and three sand ridges below the top of the slope along that fence trending W.N.W. – E.S. E. This septarium was stained green mainly by moss and by a decayed film of hemispherical pyrite. The claystone matrix had weathered into sharply defined one mm and 5 mm diameter burrows between thin pale orange (10YR 8/2) calcite veins. Where there was no green stain, the claystone had weathered light brown (5YR 6/4), between the greyish red to brown joint colours produced by pyrite oxidation (measured on dry clean joints as 10YR 6/6), 10YR 5/4, 5R 4/2 and 10R 4/6). When fractured the claystone matrix was still light brown and showed a section of an aragonite gastropod shell, without a pyrite cement, resembling the Scaphander polysarcus illustrated by Rayner et al. (2009) from Kent, but smooth. An adjacent fragment of a septarium matching the trace fossil preservation, but lacking the pyrite weathering staining, probably came from the same concretion. This fragment resembled the Rosedale Court septaria colouration being brown (5YR 5/2) to orange grey (10YR 7/2).
The approximate elevations of the Love Lane and lower A127 ditch septaria were respectively deduced from contours on the 1999 O.S. Explorer 1:25,000 series map 175 to be 50 to 54 m O.D. A third site outside 286 Eastwood Road in Rayleigh was estimated from spot heights along that road on the 1:2500 senses O.S. map to be one metre below the central road elevation there of c.52.0 m O.D. Other finds were in ploughed fields south of Bull Lane only rising to about 47 or 48 m O.D., some distance below the ridge and springs taken to be the basal Claygates on B.G.S. maps there. Putting this altitude data together, these septaria finds define a dip gradient around one in 282 to the north of a strike of about 113° E. of N., implying that they are about 123.3 m above the base of the London Clay when projected to the Burches well. The same type of septaria, separated by small decayed and haematite-replaced pyrite nodules in an otherwise barren 3m clay insitu face, occurs at about 24 m O.D. beside the Wilson Road Flagpole in Southend. Since that site was found my me first I have tended to call all of these septaria the Wilson Road bed and to try and deduce their elevation up the London Clay from a Southend well record of the base at –96.7 m O.D. The dip there is clearly to the S.E., but the angle is rather unclear near the potentially deformed old cliff. However, estimates from both areas around 123 m up the London Clay would place the Wilson Road bed within ten metres of the top of the London Clay s.s. at Hadleigh, in unit SH-12 of King (1984) in Kent, with the Kingsley Wood fossil bed right at the top of SH-12 if at 61 m O.D. as reported.
Further Reading
BRISTOW, C.R., ELLISON, R.A. & WOOD, C.J. 1980. The Claygate Beds of Essex. Proceedings of the geologists’ Association 91(4): 261-277.
KING, C. 1984. The stratigraphy of the London Clay Formation and Virginia Water Formation in the coastal sections of the Isle of Sheppey (Kent, England) Tertiary Research 5(3): 121-158.
LAKE, R.D., ELLISON, R.A., HENSON, M.R. & CONWAY B.W. 1986. Geology of the country around Southend and Foulness. Memoir for 1:50000 sheets 258 and 259, New Series. British Geological Survey vii + 85 pp.
LANE, E.H. & FITZGERALD E. 1991. Rayleigh a Pictorial History. Phillimore Chichester 124 pp.
RACKHAM, O. 1986 The ancient woodland of England. The woods of South- East England. Rockford District Council iii & 120 pp.
RAYNER, D., MITCHELL, T., RAYNER M. & CLOUTER, F. 2009 London Clay fossils from Kent and Essex. Medway Fossil and Mineral Society Rochester 228 pp.
WHITAKER, W. & THRESH, J.C. 1916. The water supply of Essex, from underground sources. Memoirs of the Geological Survey of Great Britain, 1-510. Pl.1-4.
WOOLDRIDGE, S.W. 1923. The Geology of the Rayleigh Hills, Essex with a report on excursion Saturday June 23rd 1923. Proceedings of the Geologist’s Association, 34(4): 314-322.
WOOLDRIDGE, S.W. 1924. The Bagshot Beds of Essex, Proceedings of the Geologist’s Association 35(4): 359-383.
WOOLDRIDGE, S. W. & BERDINNER, H.C. 1925. On a section at Rayleigh, Essex showing a transition from the London Clay to Bagshot Sand Essex Naturalist 21: 112-118.
On July 7, 1966, on a school coach ride from Southend to Portsmouth armed with the British Geological Survey 10 miles to the inch map of England, I made the following initial comments in my notebook: “Eastwood London Clay, Progress Road,….Rayleigh Weir, Bagshot sands, farmland arable.’’
Before 1922, the Ordnance Survey mapped a lane rising from 144 feet O.D. (44 m) at a bend in the western plain mapped previously by B.G.S. at the base of the Bagshot Beds, past 164.6 feet (50 m O.D.) at the lowest corner of Kingsley Wood, where later B.G.S. maps mark the base of the revised boundary termed lower Claygate Beds (Bristow et al. 1980), to an eastern summit height of 228 feet (69 m) on the only part of this lane which now exists. It is now a footpath between the west end of Kingsley Avenue and the eastern end of the south cutting made in 1922-3.
It must have been here, where there is a modern O.S. spot height in the A127 road surface 60.4 m O.D., 110 m N.W. of the end of the cutting at the truncated lane, that Eocene fossils were dug up by spadework in 1922-3. The present south cutting, now mature woodland with soil cover, was made then by loading the clay directly on to narrow gauge railway waggons, transporting it along what is now the south cycle track to an embankment in the western marshy plain. According to the resident road engineer, Mr. Thomson, “all the fossils come from one thin bed which was encountered at the base of the cutting at the highest point of the road (200 ft. O.D.)” (Wooldridge & Berdinner 1925). This is not literally the highest point, which was at around 230 feet beyond the cutting where the unweathered partly pyritic and largely uncemented marine aragonitic shell would not have been preserved. However, it is also not at the Grid Reference TQ 7940 8986 cited for the fossils by Bristow et al. (1980), about 150 m to the N.W. on the upper slope of the north cutting.
A photograph taken around 1930 from the end of the truncated lane shows both cutting with a thin cover of grass and denser older vegetation on a 2 m bank starting at a lane on the west end of the south cutting (photograph 108 of Lane & FitzGerald 1991). That marks an old field boundary, since removed and on my visit consisting of a small extension of the cycle track with barren brown clay and bricks dumped in it. The opposite side of the road is seen in profile on the photograph slightly nearer to the camera as a steep rise, followed by a more concave grass slope rising at about 55 m O.D. into a more gentle slope still covered with a line of dense bushes then not removed. Above them was the power lines remembered from my youth and present in 2010 on replaced poles running across a cleared corner of the enlarged 1938 cutting (from posts 13 to 15 on the edges of it). Slumped orange sands and clays are present in that corner of the cutting rising to the 70 m O.D. contour line. It was made in 1938 to add a north lane and cycle track up to 2m above the south lane of the A127 on the curved illustrated slope, removing a lower part of Kingsley Wood (not appearing to have large trees on it in photograph) and the upper line of bushes running eastwards.
My interest in visiting these cutting started on March 17, 2010 when I was shown a Cimomia imperialis (J. Sowerby) aragonite nautiloid shell, collected there in 1922 by W. H. Borke. He worked for the Rayleigh Builder J. T. Byford rather than as part of the labour force travelling from London on this Government make-work-project. The outermost septum on three half-whorls of the internally unbroken, hollow phragmocone, had an undistorted breadth of 97 mm, an incomplete venter to coiling axis radius of 68 mm. The next whorl had corresponding dimensions of 63 mm breadth half a whorl beyond a 45 mm radius showing around one of about 8 mm blocked by grey claystone. There measurements are adjusted in my entry on nautiloid shell calculations a height in the median plane of 24 mm. The third whorl with a radius of 23 mm showed the siphuncle between a tangential view of the septa. The 18 mm diameter umbilicus was open.
Doubts had previously been raised about the stratigraphy of these fossils, said to come from the Claygate Member of the London Clay Formation in current B.G.S. nomenclature based on Bristow et al. (1980). In the Hadleigh (Sand Pit Hill) B.G.S. borehole, only three km to the south, the glauconitic sands defining the base of the Claygate Member were 132 m above the base of the London Clay, with both pyrite and calcite septarian concretions in clays around 135 m, and sands with iron pan cementation defining the base of the Bagshot Formation at 149.6 m (Lake et al. 1987, p. 70-71). But according to a reliable well record, from Burches Farm in Whitaker & Thresh (1916), marked on B.G.S. 1:50,000 series sheet 258/259 0.4 km west of the Esso station at the A127 opposite Kingsley Wood, the base of the pure London Clay at –68.8 m O.D. would only be about 120 to 140 below the Claygate Member and Bagshot sands mapped there. Elsewhere in the Rayleigh Hills, Eastwood and in the Southend cliffs, I had recognized from septarian calcite marker beds that mapped correlations based on similar-looking sand layers and spring lines were not correct when they opposed the well data in this way. In central Rayleigh there were three occurrences of septaria, 1) a sandy unlaminated variety weathering yellowish orange ( 10YR 7/6) around a darker brown core in the highest levels of Rayleigh Station Carpark, 2) a fine-grained claystone with an orange (10YR 8/4) exterior, around a rather dull-looking interior (10YR 7/4 – 10YR 6/4) contrasting with thick moderate yellow brown (19YR 5/4) calcite veins and dark olive grey (5Y 3/1) jointing, at 60 Love Lane, 6 metres higher than the lowest of the carpark fins and 3) septaria of intermediate grain size, with Chondrites burrows more strongly weathered out than at Love Lane and containing Teredolites borings in wood, in a thin clay layer close to the 217 foot O.S. spot height on the Hockley Road, in the new entrance to Rosedale Court. This entrance also showed dumped bricks etc. But when the adjacent field was excavated in May, it also showed Eocene clays at 66 m O.D. The Cimomia shell was only cemented by a thin film of locally hemispherical pyrite, covered by a 5 mm of grey fine-grained and internally smooth calcite rim cement, and like benthic shells seen in November 1991 in the Essex Field Club collection at Stock Street (West Ham) did not come from any kind of large claystone concretion at Kingsley Wood. However, it did seem worthwhile looking to see if the cited altitude corresponded to these markers or other features here.
On going to the area on April 10, I found that three different temporary excavations yielded samples of interest, near but not in the A127 cuttings. The highest level of Rayleigh Carpark had again been dug up and showed parts of the septaria seen before higher up the same bank with some sands and silts, above brown clays. Probably it’s this horizon which B.G.S. takes as the base of the Claygates on the A127, perhaps with a local increase in sand thickness there. I would correlate it with unit SH-11b of King (1984) and my MacMurdo Road bed. A clay ditch (less than one m) had been dug from the fence of the A127, 40 of my paces (0.84m) N. W. from the old field boundary with the clay dumped in it at 55 of my paces from the next old field boundary defined now by the edge of the Esso Station on a nursery exit. Exactly under the fence there was a relatively fine-grained and wet clay, yielding a large fragment of a septarium of the Love Lane type matching the colour of the host brown clays when wet and inconspicuous. A decayed pyrite nodule and a smaller similar fragment of probably the same concretion were found loose in the bank disturbed by the exit of digging machine. When dried the larger fragment showed a tabular exterior surface of 2-4 mm, diameter low Chondrites coloured greyish orange (10YR 7/4) like interior matrix surfaces between the open septarian cracks of 10 mm width, showing olive grey (5Y 4/1) jointing around harder 3 mm, fine-grained smooth white calcite rim cements. When broken open the claystone matrix was locally white and more generally coloured yellowish brown (10YR 6/4), with no obvious sedimentary lamination or macrofossils. The upper parts of the ditch, extending for 170 paces, was of interest in showing none of the sand layers seen slumped down below the top of it on the opposite slope.
A third sampled exposure was for new gas mains along Rayleigh High Road and included a shallower branch also of only about one metre depth into Weir Farm Road where the surface altitude can be deduced to be at 66 m O.D. from a spot height at 67.4 m O.D. on the adjacent yellowish orange (10YR 6/6) sandy ridge where Glassey Road joins the High Road. The lower excavation showed some of these sands and iron pan; but mainly consisted of a well sorted 0.1 mm diameter quartz sand, with abundant similar-sized black and scarce green grains of less altered glauconite, giving it a homogeneous yellowish grey (5Y 7/4) colour when dry, and locally black when dug up. This lithology looked like glauconitic sands at Springwater Road in Eastwood, which has previously been mapped a few metres above the base of the Claygate Beds, rather than just under the Bagshot Beds. Later in April 2010, I attempted to level across from the septarium site on to the opposite north cutting, where both loose septaria fragments and slumped overlying sand ridges were observed. The highest and most interesting concretion was three of my nominally 1.78 m eye levels about the septaria site and 59 paces from the north cycle track, about level with the lowest ridge containing sand at the higher of two bends in the Kingsley Wood boundary fence at power line post 15, five eye-levels and three sand ridges below the top of the slope along that fence trending W.N.W. – E.S. E. This septarium was stained green mainly by moss and by a decayed film of hemispherical pyrite. The claystone matrix had weathered into sharply defined one mm and 5 mm diameter burrows between thin pale orange (10YR 8/2) calcite veins. Where there was no green stain, the claystone had weathered light brown (5YR 6/4), between the greyish red to brown joint colours produced by pyrite oxidation (measured on dry clean joints as 10YR 6/6), 10YR 5/4, 5R 4/2 and 10R 4/6). When fractured the claystone matrix was still light brown and showed a section of an aragonite gastropod shell, without a pyrite cement, resembling the Scaphander polysarcus illustrated by Rayner et al. (2009) from Kent, but smooth. An adjacent fragment of a septarium matching the trace fossil preservation, but lacking the pyrite weathering staining, probably came from the same concretion. This fragment resembled the Rosedale Court septaria colouration being brown (5YR 5/2) to orange grey (10YR 7/2).
The approximate elevations of the Love Lane and lower A127 ditch septaria were respectively deduced from contours on the 1999 O.S. Explorer 1:25,000 series map 175 to be 50 to 54 m O.D. A third site outside 286 Eastwood Road in Rayleigh was estimated from spot heights along that road on the 1:2500 senses O.S. map to be one metre below the central road elevation there of c.52.0 m O.D. Other finds were in ploughed fields south of Bull Lane only rising to about 47 or 48 m O.D., some distance below the ridge and springs taken to be the basal Claygates on B.G.S. maps there. Putting this altitude data together, these septaria finds define a dip gradient around one in 282 to the north of a strike of about 113° E. of N., implying that they are about 123.3 m above the base of the London Clay when projected to the Burches well. The same type of septaria, separated by small decayed and haematite-replaced pyrite nodules in an otherwise barren 3m clay insitu face, occurs at about 24 m O.D. beside the Wilson Road Flagpole in Southend. Since that site was found my me first I have tended to call all of these septaria the Wilson Road bed and to try and deduce their elevation up the London Clay from a Southend well record of the base at –96.7 m O.D. The dip there is clearly to the S.E., but the angle is rather unclear near the potentially deformed old cliff. However, estimates from both areas around 123 m up the London Clay would place the Wilson Road bed within ten metres of the top of the London Clay s.s. at Hadleigh, in unit SH-12 of King (1984) in Kent, with the Kingsley Wood fossil bed right at the top of SH-12 if at 61 m O.D. as reported.
Further Reading
BRISTOW, C.R., ELLISON, R.A. & WOOD, C.J. 1980. The Claygate Beds of Essex. Proceedings of the geologists’ Association 91(4): 261-277.
KING, C. 1984. The stratigraphy of the London Clay Formation and Virginia Water Formation in the coastal sections of the Isle of Sheppey (Kent, England) Tertiary Research 5(3): 121-158.
LAKE, R.D., ELLISON, R.A., HENSON, M.R. & CONWAY B.W. 1986. Geology of the country around Southend and Foulness. Memoir for 1:50000 sheets 258 and 259, New Series. British Geological Survey vii + 85 pp.
LANE, E.H. & FITZGERALD E. 1991. Rayleigh a Pictorial History. Phillimore Chichester 124 pp.
RACKHAM, O. 1986 The ancient woodland of England. The woods of South- East England. Rockford District Council iii & 120 pp.
RAYNER, D., MITCHELL, T., RAYNER M. & CLOUTER, F. 2009 London Clay fossils from Kent and Essex. Medway Fossil and Mineral Society Rochester 228 pp.
WHITAKER, W. & THRESH, J.C. 1916. The water supply of Essex, from underground sources. Memoirs of the Geological Survey of Great Britain, 1-510. Pl.1-4.
WOOLDRIDGE, S.W. 1923. The Geology of the Rayleigh Hills, Essex with a report on excursion Saturday June 23rd 1923. Proceedings of the Geologist’s Association, 34(4): 314-322.
WOOLDRIDGE, S.W. 1924. The Bagshot Beds of Essex, Proceedings of the Geologist’s Association 35(4): 359-383.
WOOLDRIDGE, S. W. & BERDINNER, H.C. 1925. On a section at Rayleigh, Essex showing a transition from the London Clay to Bagshot Sand Essex Naturalist 21: 112-118.
Mammoth bones from Southend Beach
My walk of May 19, 2009 was along all the Southend-on-Sea beaches at the latest high tide mark (relatively low 4.6 m predicted range). It started with the discovery of a fossil elephant limb bone fragment on East Beach near the Sea Life Centre. Although formal identification depends on the discovery of the teeth, it seems probable from the size and degree of secondary post-depositional dark phosphate cementation of the white bone, that it came from the Steppe Mammoth Mammuthus trogontherii Pohlia. Mammoth species are not generally as large as modern African Elephants, but this particular species was as large as the largest known specimens in the larger sample known to Big Game Hunters and culls in Africa. It was at least 14 feet (14.3m) high at the shoulder and yielded a more intact thigh bone (femur) from Mundesly Beach (Norfolk coast) with a length of 5 feet (1.5m) [A. Lister & P. Bahn Mammoths, MacMillan N.Y. 1994, p.24 x 68]. The East Beach fragment looks like the part of this femur, which is anticlastically curved as it expands into the base of the epiphyses. It has a transverse radius of curvature of 0.116 metres, indicative of a circumference approaching 0.73 m even on the narrower shaft. The axial length parallel to the trabeculae (spaced 1.0± 0.2 mm apart) is 125 mm and a width around 80 mm. The hidden thickness of the bone around the missing marrow cavity is 25 to 30 mm. It shows a transition from a smooth cortex to the pores with 0.3 mm sand, cemented by hydrated iron oxides. The Mundesly bone photograph suggests that a circumference in the unfolded anticlastic region near the epiphyses of around 0.73 m, is equivalent to a minimum shaft circumference around 0.55 m in a femur of 1.5 m length.
A second bone fragment came from the strandline between Walton and Lynton Roads, during a walk on June 26, 2009. This represents the more externally porous surface of an epiphysis with a radius of curvature of only 30 mm. Being less cemented it probably came from a younger Pleistocene deposits than the Cromer Forest-Bed yielding M. trogontherii and the straight Tusked Elephant Palaeoloxodon antiquus (Falconer & Cautley)[another possible source of large bone fragments]. This smaller bone fragment (63 by 38 by 34 mm dimensions) could easily be confused with the pebbles of aerated concrete building blocks often seen in the same strandline; but it differs from them in being denser than seawater and having elongated pores.
The reason why these bones occur at Southend is that gravel was dredged from the North Sea and pumped from the dredgers to reinforce the beach in a large diameter pipeline. The pipeline was moved west from St. Thorpe Hall Avenue to Southend East Beach during the summer of 2002. I visited East Beach showing underlying London Clay when this was going on in June 21, 2002. Due to the gradual process of deposition of new gravel (from east to west if my memory is correct) there are different fossils and concretions related to particular spots along the strandline, even though all of them have been dredged from the North Sea sites. One can deduce that the source seabed was a thin or partial cover of flint and sarsen gravel on London Clay containing concretions, some concretions were bored in the North Sea by the modern bivalve Barnea pendula Pennant. According to Jeff Saward, who collected from the Southend beach in the winter of 2002-3, this source area was “12 miles of Felixstowe” and yielded a mammoth tooth as well as mammoth bone to him then (see report on his talk of September 2003 by Roger Coleman on pages 3-4 of Essex Rock and Mineral Society Newsletter, Number 237, October 2003)
Outside the area between central Thorpe Bay and Southend Pier, gravel has been added from time to time by trucks from other sources, which do not appear to contain large fossils. Here the London Clay is still present on the beach and is still a source of the grey insitu finds still also available at East Beach in 2010.
A second bone fragment came from the strandline between Walton and Lynton Roads, during a walk on June 26, 2009. This represents the more externally porous surface of an epiphysis with a radius of curvature of only 30 mm. Being less cemented it probably came from a younger Pleistocene deposits than the Cromer Forest-Bed yielding M. trogontherii and the straight Tusked Elephant Palaeoloxodon antiquus (Falconer & Cautley)[another possible source of large bone fragments]. This smaller bone fragment (63 by 38 by 34 mm dimensions) could easily be confused with the pebbles of aerated concrete building blocks often seen in the same strandline; but it differs from them in being denser than seawater and having elongated pores.
The reason why these bones occur at Southend is that gravel was dredged from the North Sea and pumped from the dredgers to reinforce the beach in a large diameter pipeline. The pipeline was moved west from St. Thorpe Hall Avenue to Southend East Beach during the summer of 2002. I visited East Beach showing underlying London Clay when this was going on in June 21, 2002. Due to the gradual process of deposition of new gravel (from east to west if my memory is correct) there are different fossils and concretions related to particular spots along the strandline, even though all of them have been dredged from the North Sea sites. One can deduce that the source seabed was a thin or partial cover of flint and sarsen gravel on London Clay containing concretions, some concretions were bored in the North Sea by the modern bivalve Barnea pendula Pennant. According to Jeff Saward, who collected from the Southend beach in the winter of 2002-3, this source area was “12 miles of Felixstowe” and yielded a mammoth tooth as well as mammoth bone to him then (see report on his talk of September 2003 by Roger Coleman on pages 3-4 of Essex Rock and Mineral Society Newsletter, Number 237, October 2003)
Outside the area between central Thorpe Bay and Southend Pier, gravel has been added from time to time by trucks from other sources, which do not appear to contain large fossils. Here the London Clay is still present on the beach and is still a source of the grey insitu finds still also available at East Beach in 2010.
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