5.6.5 The structual stone

by G.D. Gaunt


A little over two tonnes of stone was recorded during the 1994 excavation. Most of the stone was recovered from later Roman contexts alongside the Roman road, particularly the excavated foundations of Building A (Period 4.1) and the dumps to the south (Period 5.1). A smaller concentration of stone came from Building C (Period 3.2).

Constructional stone

The vast bulk of the in situ building stone was Jurassic Oolitic Limestone. In the trans-Humber region oolitic limestone of this type occurs only in the upper part of the Middle Jurassic Lincolnshire Limestone. For historical reasons this stone is called the Hibaldstow Limestone in northern Lincolnshire and the Cave Oolite in south-eastern Yorkshire (Gaunt et al. 1992, 46-52). Outcrops of Cave Oolite between South Cave and Brough have been extensively quarried; some of the quarries are thoroughly degraded and obviously of considerable age. With this ready availability of Cave Oolite so near to Brough, it is assumed that the stone came from a local source rather than from outcrops of Hibaldstow Limestone south of the Humber estuary.

Although Jurassic Oolitic Limestone could be easily squared into blocks, it was often employed unshaped in low-status structures. The latter is largely the case on this site, where it primarily formed the footings of Building A and the post-hole packings in Building C. The exception is a fragment that appears to have been shaped on one surface, but this was in the late Roman roadside dumps and was probably derived from the walled area (1065). There was also a possible pot lid (1019, sf207). Several fragments have thin, slabby shapes that suggest use as roofing material, but this usage is unknown elsewhere, and the Cave Oolite does include layers that are thin-bedded. The oolitic limestone may have been used in the production of mortar, as another stone has mortar containing ooliths adhering to it.

Of the other stone types, Jurassic Minutely Bioclastic Limestone was the most common with less than 200kg. This stone underlies the Jurassic Oolitic Limestone on either side of the Humber, and it is assumed that it was extracted locally rather than in Lincolnshire. It would have been exposed in the quarries north of Brough by even shallow quarrying for oolitic limestone. Although of inferior quality to the latter as building stone, it would have been an adequate substitute as unshaped pieces used in low-status buildings or in foundations. This appears to be the case on this site, as it was found in conjunction with the oolitic limestone in Building A and the late Roman dumps. However, it is not present elsewhere on the site, including Building C. This could mean that it was not exploited until the later 3rd century after the oolitic limestone beds had been exhausted, although the small sample size leaves this open to debate. None of the pieces show any signs of deliberate shaping, although the shape of one item (1046, sf173) would lend itself to use as a pot lid.

A small quantity of Elland Flags-type Sandstone was recovered. This type of sandstone is present in many parts of the Upper Carboniferous Coal Measures of the Yorkshire-Derbyshire coalfield. Because of its fissility, it was used as a high-quality roofing material and, to a much lesser extent, as paving or flooring during the Roman period; it is a common find on sites in York. This high-quality building material was found in the late Roman roadside dumps, which suggests that it was derived from high-status buildings within the walled area. The large surfaces of one fragment (from context 1019) may have been used for honing.

Erratics and other incidental types

The Humber gap area contains a wide variety of erratics in the local Quaternary deposits (Gaunt et al. 1992, 109-27). The erratics were derived from sources throughout north-east England and south-east Scotland. Most of the stone items from this site that have shapes diagnostic of erratics, including belemnites and a Gryphaea bivalve, represent lithologies that are present in the local erratic suite.

Fragments of mudstone (from contexts 1000, 2061 and 2088) are almost certainly derived from either Upper Carboniferous or Lower Jurassic sources. Coal items (from contexts 1294 and 1390) are probably from Coal Measures sources (Gaunt et al. 1992, 54). Both mudstone and coal are generally too fragile to survive as erratics. On the other hand, it is unlikely that they would have been brought in from a distant source; the local clays would have been much more suitable than the mudstone for ceramic production, and there was insufficient coal to suggest acquisition for fuel. However, there are local concentrations of mudstone and coal in the Humber area, so a local source is the most likely explanation for the presence of these items.

Two Oolitic Ironstone fragments (from contexts 1098 and 2094) are from Lower Jurassic ironstone sources. These outcrop mainly to the south of the Humber, although there is an outcrop of Marlstone Rock near South Cave. In fact, the shape of the item from context 2094 suggests that it is an erratic, so it is conceivable that they were glacially derived from the Lower Jurassic Cleveland Ironstone in north-eastern Yorkshire. Eight items (from contexts 1001, 1040, 1132, 1149, 1206, 1465, 2001 and 2051) are stones of uncertain origin that have been subjected to heating. Two of the pieces (from contexts 1465 and 2051) appear to be partly roasted Lower Jurassic oolitic ironstones.


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Last updated: Tue Nov 28 2000