Thursday, February 08, 2007

Comparison of Rayleigh and Eastwood Churches

December 22 2006. Measure all the London Clay concretions seen in the exterior of St. Lawrence and All Saints Church, Eastwood in Essex for comparison with Prittlewell Priory who held it as a chapel from about 1110 to the establishment of a rector in 1248. Probably this means that the Cluniacs were given what is now the Norman Nave built a few years earlier and that no further work was done with the tithes until the independent rector added the present Tower, Chancel and South Aisle walls, described as early 13th Century in architectural guidebooks. There are some later walls and an entirely red brick 16th Century South Porch which contain no London Clay materials; the bricks probably being made for sands and flint gravels of the second terrace mapped by the Geological Survey around the brook 0.3 to 1.1 km west of the church. These bricks have a similar colour on fresh faces (10R 6/6) to those made from well sorted coarse silts and very find sands of the Eocene Claygate Member in the Rayleigh South Porch, but contain obvious white and black pebbles in old bricks of dimensions 214 mm by 105 mm by 57 to 62 mm. Associated finer-grained bricks with dimensions 226 mm by 105 mm by 47 mm also have Pleistocene-derived flints in them. The Rayleigh South Porch is said to date from just before 1497 and has a granule-grade grog consisting of iron oxide concretions, yellow laminated sand clasts and similar sandy clay flakes; all of which could have come from the Claygate Member of the London Clay exposed around Rayleigh Church and Castle. The average and more uniform brick dimensions in that porch are 218 mm by 116mm by 58.5 mm. Previously measured Rochford Church tower bricks of similar age averaged 233 mm by 116 mm by 58.5 mm, and are derived from Pleistocene silts and sands in the Rochford Buried Channel under both Rochford and Eastwood Churches. At Rochford the coarse particles or grog included by the brickmakers consists of white and grey sandy clasts of dimensions 6 mm by 5 mm presumably made from calcareous concretions or previously dried silts of Pleistocene age. The Rochford tower was built for the grandfather of Anne Boleyn who died in 1515 and unlike the Eastwood and Rayleigh Churches his brickmakers made additional black bricks of similar size to produce diapers on the red brick tower. At Rayleigh this pattern was made in or shortly after 1515 by placing black flints among the Kentish Ragstones and septaria of the Alen Chapel, east chancel wall and some buttresses. It was not attempted in the South Porch probably because it was built before that fashion had developed and it was attempted at Eastwood.

Turning now to the London Clay concretions there is just one seen in the largely hidden walls of the Norman Nave. Since it contains no thick veins on the original exterior and differs in colour from those in the 13th Century walls it may perhaps be regarded as a questionable septarian record. The average colour measured from three parts of it in the freezing fog is 5.0YR 3.67/3.33 and in a previous visit in the bright afternoon weather of October 3 2005 it averaged 6.67 YR 4.00/3.33. Two parts of it were recorded as dark yellowish orange (10YR 6/6) and blackish red (5R 2/2) in both weather conditions by holding the Rock Colour Chart colours in the same light as the wall enveloped by the grey background cardboard of the chart. A third area of the concretion was recorded as Greyish Red (5R 4.2) in the sunshine and as the reddish brown (10R 3.2) today. With more experience I think that this concretion is from the London Clay, probably from Southend, and matches the red variety seen in Leigh Church tower, the Norman walls at South Church and Sutton churches and some of the Prittlewell Priory and Rayleigh Church septaria. By contrast the London Clay concretions in the Chancel and South Aisle at Eastwood are of a different colour and provinance with an average colour of their matrix measured today from 8 fragments and 24 areas of colour as 7.708 YR 6.208/3.33, changing to 7.692 6.269/3.341 with the addition of two vein colours seen on one of them (marginal prisms 5Y 8/1, central prisms of upsplit 4 mm thick vein 10 YR 6/6). Bearing in mind how small and scarce these concretion fragments were one should not assume that they do not come from thicker veined concretions seen at Southend, or were not bored by modern beach organisms. On December 14 and 18 I revisited Rayleigh Church and recorded all the colours on the London Clay concretions in the lower external wall of the most eastern of the four bays in the South Aisle, and also in what appears to be a later wall built around the post-1394 Ragstone tower forming a thicker west wall of the western bay to the South Aisle. The eastern bay include previously fallen concretion fragments showing Eocene high spired microgastropods (perhaps Litopia sp. or Spiratella tutulina (curry) and the west wall shows some calcite replaced wood with bivalve borings of Eocene age in it (3 mm diameter Teredolites longissimus Kelly and Bromley. The claystone matrix of the fallen fragments, of both grey unweathered and red veined lithology is full of coarse silt and very fine sand in a bioturbated clay matrix. The veins all have a pale yellow prismatic margin, followed by dark orange as at Eastwood, and then when thick enough another pale layer of open scalecohedral calcite prisms with a dark surface on the open vein. In one case this dark manganiferous oxide layer was overgrown by a 20 mm diameter rostette of white barite fibers, as at Prittlewell Priory. In terms of the average colours of the matrix and jointing in the western wall of the South Aisle was 2.22 Y 6.833/2.500 (18 determinations), the new insitu measurements of east bay 8.65 YR 6.294/3.024 (85 determinations) and the December 4 Choir Vestry 10.0 YR 6.229/3.057 (35 determinations). They all show the same sequence of veins and I do not doubt that all these walls were built from the same concretions, probably present on the site and perhaps left institu in the east bay wall when the church was repaired and extended in 1394. The sequence of vein cements is most characteristic at Rayleigh and obviously produced a variable average vein colour there recorded as follows: west wall (5) 9.00 YR 6.200/4.800. East Bay (20) 0.30Y 6.100/2.900, choir vestry (4), 2.50Y 7.500/3.000. This was an exposure of highly disturbed brown London Clay with similar thick-veined septaria of grey to brownish red colour on the upper beach about 110 metres east of Crowstone Avenue on December 20th and I intend to compare the samples to these similar-looking Rayleigh and Eastwood Church septaria over the holiday when dried.