Archeologie in Vlaanderen IV - 1994, 237-251

Petrology and Provenance of Unworked Stone from the Medieval Fishing-Village at (mun. of Oostende, prov. of West )

Paul De Paepe1 & Marnix Pieters

1 Introduction from Westende to Oostende. Testerep was separated from the mainland by the Groot Geleed, a creek Since the spring of 1992 a team of the Institute that joined the river IJzer to the west. for the Archaeological Heritage (I.A.E) conducted During the 14th-15th centuries Testerep was by the second author and working in close collab­ repeatedly ravaged by high spring-tides and storms oration with the Provincial Government of West which badly damaged the former coastline. Many Flanders has been carrying out archaeological ex­ pieces of land, including parts of Walraversijde, dis­ cavations at Raversijde2. The excavation site is pardv appeared with their settlements into the sea4. In located in die Provincial Domain of Raversijde and diese places the resident population had to move uncovers remains of a medieval fishing-village inland to save their lives and belongings. The con­ 1 Universiteit Gent, Vak­ known in historical sources as Walmversijde'*. struction of the 'Gravejansdyke' probably has to groep Geologie en Bodem­ kunde, Laboratorium voor Archaeological records of the sixties and seven­ be situated in this context. Mineralogie, Petrologie en ties with regard to the present-day beach of Raver­ The archaeological finds fit in with these historic Micropedologie, Krijgslaan sijde, made by E. and A. Cools-Mortier, suggest events. Coins recovered from the site of Walraver­ 281, Gebouw S8, B-9000 that the earliest human occupation at Walraversijde sijde were mainly struck during die reign of John Gent, . 2 the Fearless (1405-1419) and his son and successor Pieters 1993 & 1994. dates back to the 10th-12th century. At that time 3 Verhulst 1964. the village was situated on the former island Philip the Good (I4I9-I467). They testify that the 4 Choqueel 1950. Testerep, which faced the coastline and extended inhabitation of the inland area began with the build­ ing of the Gravejansdyke in die earl}' 15di century. The area under study was left again towards the end of the 15th century. This may be linked up widi the military troubles with Maximilian of Austria at that time in the Franc of Bruges. About 50 ares of the inland pan of the mediev­ al settlement of Walraversijde have been unearthed thus far, revealing the ground-plan of fifteen houses and a variety of mobile archaeologica. The latter include pottery of both local and exotic origin, metal artefacts, vegetable remains, bone material, shells, pit-coal and other rock material, many of them being related to fishing activities (fish-hooks, weights for fishing-nets, piercers, etc.).

1 The rock concentration uncovered in the ditch located between buildings 1 and 10. De concentratie stenen ontdekt in de grachtopvulling tussen de gebouwen 1 en 10.

237 P. DE PAEPE & M. PIETERS

As the application of techniques from the phys­ 2 Aims and scope of the study ical sciences to archaeological finds provides an in­ dependent means of unlocking information about The eighty-four stones examined were collected man's past and our palaeoenvironment, it was de­ in the 3 to 4 metres wide ditch which parcels out cided by I.A.E to call in the expertise of analytical the thus far unearthed part of the medieval dwelling scientists to investigate organic and anorganic site of Walraversijde into three 'dwelling islands'. materials assembled within the framework of the They were recovered between building 1 and build­ research programme presented above. This paper ing 10, where they formed a unique rock concen­ deals exclusively with data emerging from the pet- tration (fig. 1 en 2). The stones show no working rologic study of rock samples found in the course traces and are thought to have been rounded by of the second excavation campaign (April-Octo­ geological agents. The function of the finds still ber 1993). remains uncertain although it has been suggested5 that they could have been used as ballast for ships by local fishermen. It is the main purpose of the present work to describe briefly the main categories of rock excav­ ated, to characterize them by petrographical and 2 Ground-plan of the thus far unearthed area with location of the analysed rock con­ geochemical methods, and to pin-point as closely centration. as possible their potential source area(s). Doing so, Grondplan van de reeds onderzochte zone met we hope to contribute to a better knowledge and aanduiding van de vindplaats van de bestudeer­ undersranding of the commercial practices or de stenen.

Pieters 1994, 293

238 Petrologv end Provenance of Unworked Stone from the Medieval Fishing-Village at Raversijde

Table 1 entary and metamorphic. As evidenced by table 1, The number (N) and percentages of all analvsed some rock categories occur in great proportions, stones from Raversijde according to rock type whereas others are very poorly represented. Most samples of igneous origin appear very Rock type N % similar to each other in macroscopic features. They comprise basaltic and derivative volcanic rocks and Igneous rocks 47 55.9% their hypabvssal equivalents (dolerites). A grey to volcanic (28) dark grey colour is highly characteristic and the hypabyssal (18) material is massive, rather homogeneous and fine- plutonic (I) to medium-grained depending on emplacement Sedimentary rocks 33 39.3% conditions (at or below the surface of the earth). rudaceous (1) Among the sedimentary rocks sandstones and arenaceous (16) limestones are widely distributed. Most commonly, calcareous (11) the former have greenish grev or reddish to violet siliceous (5) hues and display a complete gradation in particle Metamorphic rocks 4 4.8% size. The great majority of the limestone fragments metapelitic (2) are creamy, compact and very fine-grained. The meta-arenaceous (2) third common type of sedimentary rock is cher- tified material. The rare metamorphic specimens Total 84 100.0% forming part of the investigated collection are dissimilar as far as colour, grain size and fabric are concerned. trading activities of the inhabitants of the medieval fishing-community of Walraversijdc. 3.2.1 Igneous rock types

3 Petrology This major group is composed of twenty-eight pieces of lava, eighteen hypabvssal rock fragments 3.1 ANALYTICAL TECHNIQUES (dyke rocks) and one specimen of intrusive origin.

The rock specimens available for the present study are complete or fragmented detrital clasts in Volcanic rocks (fig. 3: a-d) the range of 1 to 20 cm that derive from pebble and cobble deposits. They show varying degrees Twelve stones exhibit an aphantic texture. The of rounding. All were thin-sectioned and examined remainder are either plagioclase phyric, olivine by transmitted light under the polarizing micro­ phyric or hornblende phyric. These direc phenocryst- scope. In addition to petrographic analysis, the bearing variants are represented by seven, eight and whole-rock chemistry of a restricted number of one piece(s) of rock respectively. specimens, selected on the basis of texture, size and weathering state, was determined using a Perkin- Mineral phases occurring in aphyric samples (AR Elmer 2380 flame atomic absorption spectropho- 4966, AR5053, AR5054, AR505'6, AR5058, AR to-meter (AAS). The method employed was devel­ 5068, AR5069, AR5071, AR5073, AR5074, AR oped bv Van Hende (1976) and calibrated using 5075 and AR5076) include variable but appreciable international reference materials. Procedural details quantities of plagioclase, opaque ore, clino-py- are beyond the scope of this work. Chemical anal­ roxenes, olivine, chlorite and calcite, which occa­ yses, CIPW norms and some useflü petrochemical sionally are associated with traces of biotite, apatite parameters (differentiation index Dl, solidification and quartz. The texture is typically intergranular, index SI and anorthitc content of the normative though in 50% of the analysed specimens the feld­ plagioclase) are given in table 2 and 3. spar ladis show a distinctive fluxion (or trachytoi- Samples numbers (from AR4965 to AR4989 dal) texture. Vesicles are uncommon, small-sized, and from AR5043 to AR5101) refer to the register and completely filled with calcite, euhedral quartz, of the Laborator}' of Mineralogy, Petrology and opaques and/or chlorite minerals. In some sec­ Micropedology (LMPM) of the University of Gent, tions intergranular and subophitic textures are seen headed by Prof. Dr. G. Stoops, where the stones side by side. are presendy stored and kept available for comp­ Plagioclase microlites are unaltered or partially arative analvtical research. replaced bv various secondary minerals, the major decomposition products being veinlets and clots of calcite and albitic feldspar. Fresh clinopyroxene 3.2 PETROGRAPHIC AND CHEMICAL DATA crystals are colourless, pale brown, purplish brown or deep lilac. Clinopyroxene pseudomorphs appear Thin-section analysis shows that the lithic mat­ to be particularly widespread and essentially made erial is of three main categories: igneous, sedim­ up of minerals of the chlorite group. Opaque ores

239 P. DE PAEPE & M. PIETERS

240 Petrology end Provenance of Unworked Stone from the Medieval Fishing-Village at Raversijde

3 Thin sections of unworked stones from Raversijde under the polarizing microscope. Slijpplaatjcs van dc nict-bewcrkte stenen uit Raversijde onder de polarisatiemicroscoop.

(a) Aphyric basaltic lava (sample AR5053). Essentially composed of (b) Plagioclase phytic basaltic lava (sample AR 4972). sub-parallel plagioclase laths, olivine entirely altered to chloritic and/or Phenocrysts of sericitized plagioclase feldspar in an intergranular iddingsite-like material, iron ore and interstitial titaniferous augite. matrix of plagioclase, augite, iron ore and interstitial chlorite. Cross-polarized light. The longer side of the view measures 5 mm. Plane-polarized light. The longer side of the view measures 5 mm. Atierische bazaltischc lava (gesteente AR5053). Bestaat hoofdzakelijk uit Bazaltischc lava met plagioklaasfcnokristen (gesteente AR4972). plagioklaaslattcn met nagenoeg evenwijdige rangschikking, olivijn dat volle­ Fenokristen van gesericitiseerde plagioklaas in ccn intergranulaire grond­ dig tot chloriet en/of iddingsiet is omgezet, ijzererts en interstitiële ritaan- massa die uit plagioklaas, augiet, ijzererts en intcrstiticel ontwikkelde augiet. chloriet bestaat. Gekruiste nicols. De lengte van de lange zijde van de opname bedraagt 5 Evenwijdige nicols. De lengte van de lange zijde van de opname bedraagt mm. 5 mm.

(c) Plagioclase phyric basaltic lava (sample AR5082). Phenocrysts of plagioclase and microphenocrysts of augite and iron ore in agroundmass of plagioclase, granular iron ore, chlorite and calcite. An amygduk with highly irregular outline filled with chlorite in the (d) Olivine phytic basaltic lava (sample AR5081). middle of the section. The cavity-filling chlorite displays a fibroradial Phenocrysts of olivine, which are entirely altered to chloritic material, pattern. enclosed in a matrix of plagioclase, granular augite, iron ore and Plane-polarized light. The longer side of the view measures 5 mm. interstitial patches of chlorite. Bazaltischc lava met plagioklaasfcnokristen (gesteente AR5082). Plane-polarized light. The longer side of the view measures 5 mm. Fenokristen van plagioklaas en mikrofenokristen van crtsmineralen en augict Bazaltischc lava met olivijnfenokristen (gesteente AR5081). in een grondmassa die uit plagioklaas, ijzcrertskorrels, chloriet en calciet Olivijnfenokristen, die volledig tot chlorietmineralcn zijn omgevormd, zijn bestaat. Een onregelmatige holte is opgevuld met chloriet (in het midden opgenomen in ccn grondmassa die uit plagioklaas, augict, ijzererts en intet- van de foto). De chlorietvulling is waaiervormig ontwikkeld. stiticlc chloriet bestaat. Evenwijdige nicols. De lengte van de lange zijde van de opname bedraagt 5 Evenwijdige nicols. De lengte van dc lange zijde van dc opname bedraagt 5 mm. mm.

(f) Subfeldspathic arenite (AR5090). (e) Hypabyssal basaltic rock (sample AR5060). Larger grains of quartz and microcline in an interlocking mosaic of Composed of sericitized plagioclase, subophitic augite, iron ore, hom­ quartz, white mica, microcline, iron oxide, calcite and a little pla­ blende, biotite and chlorite. gioclase. Plane-polarized light. The longer side of the view measures 5 mm. Cross-polarized light. The longer side of the view measures 5 mm. Bazaltisch ganggesteente (gesteente AR5060). Subveldspathisehe arcniet (gesteente AR5090). Samengesteld uit gesericitiseerde plagioklaas, subophitische augiet, ijzererts, Tamelijk grote kwarts- en mikroklienkorrels liggen vervat in een mozaiek hoornblendc, biotiet en chloriet. van kwarts, witte glimmer, mikroklien, ijzererts, calciet en wat plagioklaas. Evenwijdige nicols. Dc lengte van de lange zijde van dc opname bedraagt 5 Gekruiste nicols. De lengte van dc lange zijde van de opname bedraagt 5 mm. mm.

(h) Porphyroblastic schist (sample AR4987). Skeletal garnet porphyroblasts embedded in an aggregate consisting (g) Quartz arenite with caleite cement (sample AR4986). chiefly of quartz grains and biotite flakes. Angular quartz grains firmly cemented with granular calcite. Plane-polarized light. The longer side of the view measures 1.25 mm. Plane-polarized light. The longer side of the view measures 1.25 mm. Porficroblastische schist (gesteente AR4987). Kwartsareniet met calcietcement (gesteente AR4986). Skeletvormig ontwikkelde granaatporficroblast in een grondmassa die Hoekige kwartskorrels die aaneengekit zijn door korrelige calciet. hoofdzakelijk uit kwartskorrels en biotictlamellen bestaat. Evenwijdige nicols. De lengte van de lange zijde van de opname bedraagt Evenwijdige nicols. De lengte van dc lange zijde van de opname bedraagt 1,25 mm. 1,25 mm.

241 P. DE PAEPE & M. PIETERS

are typically granular, needle-like or dendritic. Petro­ which may form fibroradial aggregates. In some graphic evidence indicates that the primary mineral samples the latter is associated with calcite. Except assemblage of various aphyric volcanic samples in­ for AR4977, the primary olivine crystals are always cluded olivine as a major constituent. However, completely replaced by alteration products and the relicts of unaltered olivine have been detected in large variety of olivine decomposition products none of the studied sections. Olivine replacements (serpentine, calcite, chlorite, opaque ore) is a most consist of an iddingsite-like material, calcite, chlor­ striking feature of these rocks. In specimen AR ite, iron ores, serpentine minerals and/or saponites. 5051 the olivine phenocrysts form clusters giving They mimic the external crystal form of the replac­ to the rock a glomeroporphyritic texture. ed phase. Prisms of apatite were found only once In view of a more detailed characterization, four (AR4966). Sparse minute biotite flakesar e enclos­ olivine phyric samples (AR4977, AR505I, AR5064 ed in three samples (AR5056, AR5068 and AR and AR508I) displaying variable degrees of alterat­ 5076). The)- display a moderate to strong pleo- ion were analysed for their major element contents. chroism and a reddish orange maximum absorp­ The rock analyses, listed in order of increasing Si02 tion colour. content, together with a calculation in terms of the Microscopically, the aphyric volcanic rock samples standard compounds of the CIPW norm are given may be described as tholeiitic basalts (widiout oliv­ in table 2. The alkaline parentage of the analysed ine pseudomorphs in the groundmass) and alkali specimens, as evidenced by the petrographic data basalts (with Carich, more or less titaniferous augitc (in the first place the titaniferous lime-rich nature and abundant altered olivine microlites in the of the clinopyroxenes as suggested by their violet- mineral assemblage). purple colour and the widespread occurrence of The plagioclase phytic samples (AR4968, AR olivine crystals in the groundmass) is also corrob- 4971, AR4972, AR5061, AR5062, AR5065 and AR5082) are moderately to strongly porphvritic with abundant large plagioclase phenocrysts and sparse olivine and magnetite microphenocrysts set Table 2 in an intergranular matrix. The latter chiefly con­ Major element contents and CIPW norms (in wt.%) of volcanic basaltic rocks sists of plagioclase, iron ore, colourless to purplish from Raversijde (Anal. J. Van Hende). Oxide percentages were recalculated brown clinopyroxene, olivine pseudomorphs with to 100 anhydrous before assigning within the norm and normative the characteristic lozenge-shaped outline, and chlo­ compositions are calculated assuming a uniform Fe20,/FeO ratio of 0.15. rite minerals. Calcite, reddish brown biotite and sphene occur in minor proportions. Some rocks dis­ AR5081 AR5051 AR4977 AR5064 play a ver}- low vesiculation. Void fillings enclose quartz, chlorites, calcite and hematite. The sizes of Si02 44.50 45.78 47.06 47.06 the plagioclase phenocrysts van' from 0.5 mm up Ti02 1.99 1.89 2.04 2.09 to 7 mm. Some are very strongly corroded at their A1203 14.02 13.53 13.94 13.91 margins or crowded with minute glassy or opaque Fe203 6.10 3.66 3.34 5.27 inclusions. Plagioclase is variously affected by alter­ FcO 5.91 6.92 7.45 5.09 ation. The replacements include albite, sericite, and MnO 0.38 0.11 0.19 0.10 much more rarely calcite. Olivine phenocrysts and MgO 8.15 9.12 9.65 7.21 microphenocrysts (<0.5 mm) are converted into CaO 9.55 8.49 8.43 9.76 irregular aggregates of chlorite, calcite and quartz. Na20 1.93 1.60 3.01 2.14 Vein fillings are composed of quartz, chlorite and K20 1.06 1.21 1.42 0.95 opaque ore. By lack of chemical data great diffic­ P205 0.30 0.35 0.42 0.37 ulty is found to give a correct name to this second H20+ 3.62 4.75 2.25 3.19 variety of volcanic rocks. It is likely however that H20- 1.51 1.73 0.31 2.16 they mainly derive from an alkalic magma series (mosdy alkali olivine basalts) and that at least part CIPW Norms of them might properly be referred to as hawaiite or 6.68 7.74 8.68 6.01 and/or mugearite. ab 17.41 14.63 24.62 19.35 an 28.35 28.29 21.00 27.29 The examined olivine phytic samples (AR4975, nc - - 0.92 AR4977, AR5046, AR505I, AR5057, AR5064, di 16.68 12.15 15.94 17.99 AR5072 and AR5081) share the same general mi- hv 9.71 26.03 - 21.24 neralogical and textural characteristics. They carry oi 13.47 3.79 21.27 0.45 variable but usually important quantities of pseudo- tnt 2.94 2.66 2.62 2.55 morphoscd olivine phenocrysts and micropheno- il 4.05 3.87 4.01 4.23 crysts, up to 4 mm in diameter, in an intergranular 0.77 0.91 1.01 0.94 matrix of plagioclase, brown clinopyroxene, opaque ap ore, altered olivine, chlorite, brown glass and inter­ DI 24 22 34 25 stitial zeolites. Vesiculation is very low and vesicles SI 35 41 39 35 are completely filled with secondary minerals. The chief mineral phase in the amygdules is chlorite. PI (An%) 62 66 46 59

242 Petrology end Provenance of Unworkcd Stone from the Medieval Fishing-Village at Raversijde

orated by the major element composition of AR opaque granules and pseudomorphs after clinopyr- 4977, the only olivine phytic sample available for oxene (?) associated with rare apatite and brown the present study enclosing a high proportion of biotite. The phenocrystal hornblende, with tints fresh olivine and relatively few alteration products. from hazel-nut brown to almost colourless, is part­ An alkali olivine basalt composition for all olivine ially or completely transformed into chlorite, biotite phyric specimens is therefore likely and yellow epidote grains. The alkali feldspars are As compared to AR4977, the three other rock invariably strongly sericitized. The results of the analyses presented in Table 2 are lower in MgO petrographic analysis of AR5049 are consistent with and total alkalis, but higher in total iron and CaO. a quartz trachytic composition. 'Loss on ignition' values and FcjO^/FeO ratios are also significandy higher for AR5051, AR5064 and AR5081. This is in perfect agreement with die Hypabyssal rocks (fig. 3: e) microscopic observations which show that the lat­ ter arc fairly rich in hydrated secondary minerals From the textural point of view the analysed (chlorite, serpentine, zeolites, etc.) which replace hypabyssal rock samples present a rather uniform partially or almost entirely the primary ferromagnc- appearance under the microscope. Their average sian compounds of the lava. grain size ranges from 0.8 to 1 mm in the fine­ Sample AR5049 is pale grey in hand specimen, grained varieties and from 1.2 to 2.2 mm in those non-vesicular and hornblende phyric. Dispersed of medium size. There is a very large proportion of phenocrysts of hornblende (up to 5 mm in length), stones (at least 15 out of the 18 samples included opaque minerals and severely altered feldspars are in this group) composed of an interlacing network set in a fine-grained mesostasis composed of relicts of plagioclase laths, stumpy colourless or very pale of alkali feldspars, quartz, chloritized hornblende. greenish clinopyroxene grains, ore minerals in skel­ etal or individualized forms, rare pseudomorphosed olivine and irregular quartz grains, enclosed ophit- Table 3 ically by coarse plates of colourless to pale green Major element contents and C1PW norms (in wt.%) of hypabyssal basaltic clinopyroxene. In addition, intergrowths of quartz rocks from Raversijde (Anal. J. Van Hende). Oxide percentages were recal­ and plagioclase may also occur. Another minor con­ culated to 100 anhydrous before assigning within the norm and normative stituent of some sections is interstitial reddish brown compositions are calculated assuming a uniform Fe20,/FeO ratio of 0.15. biotite. In several samples the pyroxene pseudo­ morphs are heavily stippled with minute subround- AR4984 AR5059 AR5063 AR5045 AR4978 AR5070 ed sphene crystals. AR5050 is the most finegrained sample of the group and shows a prominent Si02 45.78 49.20 49.63 50.05 50.91 50.92 amygdaloidal texture. The larger amvgdules are up Ti02 3.22 2.68 2.88 2.33 2.38 2.48 to 5 mm across and filled by chlorite, calcite and A1203 16.29 13.57 13.64 13.65 13.72 13.30 quartz. Smaller ones only contain chlorite. Though Fe203 7.52 6.86 9.01 4.52 3.17 4.70 the ophitic-textured specimens have suffered severe­ FeO 6.42 6.31 4.48 7.54 9.06 7.74 ly from albitization, sericitization, calcitization and/ MnO 0.19 0.22 0.24 0.18 0.17 0.18 or chloritization, many are thought to be tholeiitic MgO 3.97 5.85 5.01 4.73 5.36 4.94 doleritcs in virtue of their primary mineralogy and CaO 6.87 7.17 6.88 9.25 6.14 6.32 texture. Na20 3.62 2.94 3.38 2.35 3.08 3.20 The group of hypabyssal rocks also includes a K20 1.42 1.58 1.18 0.53 1.13 1.91 small number of aphyric to moderately porphyritic, P205 0.53 0.37 0.42 0.32 0.28 0.28 subophitic-textured samples with strongly resorbed H20+ 2.62 2.18 2.28 2.81 3.16 2.44 phenocrystal plagioclase, up to 5 mm in length. They H20- 0.95 0.83 0.50 0.88 0.98 0.74 bear a close resemblance to some of the plagioclase phyric basaltic lavas described above. The clino­ CIPW Norms pyroxene is usually pale brown to brown purplish q - - 0.96 6.73 4.22 1.71 and in some sections olivine is a major constituent or 8.79 9.69 7.29 3.28 7.01 11.80 of the mesostasis. These petrographical features ab 32.15 25.80 29.79 20.92 27.32 28.27 are suggestive of an alkali olivine dolerite composi­ an 25.18 19.95 19.30 26.40 21.28 17.05 tion. di 6.14 12.18 11.31 16.45 7.44 11.62 One subophitic-textured rock (AR4984) and hv 2.27 22.38 21.51 17.87 24.30 20.97 five ophitic-textured samples (AR4978, AR5045, ol 14.48 0.76 - - - - AR5059, AR5063 and AR5070) were analysed mt 3.36 3.13 3.17 2.94 3.03 3.03 chemically. The results are given in table 3. The il 6.42 5.28 5.69 4.66 4.75 4.92 plagioclase phyric rock AR4984 (table 3, column ap 1.31 0.91 1.04 0.81 0.67 0.67 1) is characterized by a relative high content of DI 41 35 38 31 39 42 Al-,03, Ti02 and alkalis coupled with relativelv low SI 17 25 22 24 25 22 MgO. It difters markedly from the other samples which reveal a remarkable uniformity in the bulk PI (An%) 44 44 39 56 44 38 composition (table 3, columns 2 to 6). Unlike the

243 P. DE PAEPE & M. PIETERS

other tholeiitic doleritcs examined, AR5045 has a constituents include apatite, sphene, epidotc fairly high CaO content. This reflects the presence (pistacite) and quartz. Euhedral plagioclase pheno- of considerable calcite in interstices and cavity fillings crysts are fairly abundant, partially saussuritized and in the rock. up to 8 mm long. Hornblende phenocrysts are much smaller, less common and either euhedral or corroded. Partial replacement of hornblende by Plutonic rocks chlorite is unusual. Augite phenocrysts occur in very small quantity and are marginally converted As stated previously, this group is of litde im­ into uralite. We suspect that the primary mineral portance, one sample only (AR5048) having been assemblage of die rock contained biotitc as a major identified. In thin section it consists of phenocrys- phase but the mineral is now thoroughly altered tal plagioclase, brown hornblende and colourless into a mixture of chlorite, epidote and sphene. clinopvroxene in a dense matrix rich in plagioclase, AR5048 is termed a diorite porphyry, because of orthodase, chlorite, iron ore and actinolite. Minor its porphyritic texture and mineralogy.

4 Schematic geological map of the British Isles. Schematische geologische kaart van de Britse Eilan­ den. 1. Pliocene, Oligocene and Eocene. Pliocecn, Oligoceen en Eoceen. 2. Cretaceous. Krijt. 3. Jurassic. Jura. 4. Triassic. Trias. 5. Permian, Carbonifer­ ous and Devonian. Perm, Carboon en De- voon. 6. Silurian, Ordovician and Cambrian. Siluur, Ordovicium en Cambrium. 7. Torridonian, etc. Torridoniaan, enz. 8. Schists and gneisses. Schistcn en gncisscn. 9. Volcanic rocks: basalts, etc. Vulkanische gesteenten: bazalten, enz. 10. Intrusive rocks: grani­ tes, etc. Dieptegcstccnten: granie­ ten, enz. 11. Lough Neagh. Hct Ncagh-meer.

244 Petrology end Provenance of Unworked Stone from the Medieval Fishing-Village at Raversijde

3.2.2 Sedimentary rock types cline, plagioclase feldspar, muscovite, iron ore, tour­ maline, staurolitc, colourless garnet and exception­ The thirty-three sedimentary rock samples have ally lithic fragments (muscovite-bearing granite, been divided into four main groups: ruditcs, sand­ myrmekite, chert, phyllitic-looking aggregates). stones, carbonate rocks and siliceous rocks. The The calcite content of AR4970 is distinctly lower microscopical properties of at least one represent­ than in the foregoing rock sample although the ative sample of each group are summarized below. mineralogies of the framework grains of both are indistinguishable. The framework of AR5086, the third rock belonging to the group of quartz arenites Rudaceous rocks with calcite cement, offers a rich suite of heavy min­ erals, including essentially zircon, colourless garnet, AR4988 is die coarse-grained equivalent of a clinozoisite, epidote, sphenc, rutile, tourmaline and feldspathic arcnitc. It is composed of a chaotic as­ apatite. semblage of scattered subrounded and rounded As stated above AR4969, AR5078, AR5079 quartz, K-feldspar and quartzite grains of granule and AR5090 are rather immature sandstone variet­ size (from 2 to 4 mm across) set in a dominant ies and are interpreted as subfeldspathic and feld­ matrix of quartz, K-feldspars (including intergrowths spathic arenites. The presence of hematite in the of quartz and feldspar), sodic plagioclase, flaky dc- interstitial matrix imparts to some of these rocks trital micas (brown biotite being much more com­ (AR5079, AR5090) an intense deep reddish colour. mon than muscovite), opaques and accessory zircon. Hematite-bearing varieties are relatively coarse­ The K-feldspar clasts are usually subrounded, per- grained and may carry lithic fragments or abundant thitic and perfecdy fresh, whereas sodic plagioclase large broken microcline crystals. The lithic grains grains are subangular, twinned according to the al- embedded in AR5079 predominandy derive from bite law and occasionally sericitized. The coarser altered microcrystalline basaltic rocks. The domin­ quartz grains are either monocrystalline, with un- ant feldspar in AR5090 is perfecdy fresh microcline dulatory extinction, or polycrystalline, with sutured up to 1.5 mm across. The colour of the other feld­ crystals or individuals forming polygonized mosaics. spar-rich arenites is greenish (AR4969) or yellowish grey (AR5078). AR4969 is a poorly sorted subfeld­ spathic variety with subangular framework grains of Sandstones (fig. 3: f-g) intermediate size. The latter consist essentially of quartz and albite-twinned plagioclase and are set in Within this group of closely related rocks several an interstitial matrix rich in fibrous chlorite. This phyl- varieties could be distinguished using the amount litic mineral is accompanied with detrital distorted, of interstitial argillaceous matrix (<30 /x fraction) bent and frayed muscovite flakes,opaqu e iron ore, and the mineralogical composition of the frame­ zircon, sericite, and more sporadically with calcite. work grains (quartz, feldsparan d lithic or rock frag­ Sample AR4980 is a coarse-grained reddish vol- ments) as primary discriminators for classification6. caniclastic rock7. The lithoclasts were produced by Relying on these two criteria the analysed sand­ weathering and mechanical erosion of igneous, stones from Raversijde comprise the following var­ sedimentary and metamorphic rocks. They consist ieties: quartzites (AR4973, AR5084 and AR5087), overwhelmingly of a mixture of aphyric trachytoi- quartz arenites with calcite cement (AR4970, AR dal-textured volcanic fragments in combination with 4986 and AR5083), subfeldspathic and feldspathic porphyritic rocks of basic, intermediate and more arenites (AR4969, AR5078, AR5079 and AR felsic composition, intermediate types being largely 5090), sublithic and lithic arenites (AR4980, AR predominant. Many lava fragments are partially or 5080 and AR5085), quartz wackes (AR4967 and completely replaced by carbonate minerals. We note AR4976) and feldspathic wackes (AR5052). also a significant proportion of nonvolcanic particles, On a freshly fractured surface the colour of the including granite, chert, quartzite, micaschist, and quartzites is a very pale grey to weakly yellowish a nonfossiliferous type of carbonate rock. with occasionally some irregular orange patches. The rock fragments that are scattered through­ These rocks are microscopically almost identical out the sublidiic arenite AR5085 mainly derive from and consist of a tightly interlocking mosaic of very granitic and metamorphic sources. Detrital micas well-sorted quartz crystals 0.12 to 0.2 mm across. (both muscovite and brown biotite) are fairly abun­ In order of decreasing abundance the accessory dant and, isolated in the matrix, we have noted a minerals include opaque compounds, muscovite large garnet porphyroblast with S-shaped trails of flakes, plagioclase, microcline and zircon. quartz inclusions. AR5080 is a transitional rock The analysed calcite-cemented quartz arenites type displaying well-rounded grains of quartz cem­ are pale grey or yellowish brown in hand specimen ented by either interfering syntaxial quartz over­ 6 Classitleation elaborated depending on calcite content. AR4986 has a frame­ growths in optical continuitv or carbonate minerals. bv Dott 1964 and modified work of relatively well-sorted but irregularly shaped AR4967 and AR4976 are two pale grey quartz by Petti John « «/. 1987. According to the definit­ monocrystalline quartz grains, with an average size wackes containing a sand-size fraction that is made ion given bv Fisher 1961 and of about 0.25 mm, cemented by microcrystalline up predominandy of quartz grains of variable shape, Fisher 1966. calcite. Minor framework minerals comprise micro­ up to 2.5 mm across. Most of the quartz grains

245 P. DE PAEPE & M. PIETERS

display undulatorv extinction. Other detrital part­ eous sponge spicules and diagenetically silicified icles are rare and composed of muscovite, plagio- foraminifers and shell biodasts. Imperfectly silicif­ clase, perthite, chlorite, iron ore, tourmaline, zircon ied tests are found but appear to be extremely rare. and rutile. Lithoclasts are very uncommon. Some Very fine carbonaceous matter is randomly distrib­ derive from micaceous calc-schist deposits. The ma­ uted throughout some sections. As the samples trix of both samples consists of a microcrystalline contain originally calcareous fossil forms they are to fine-grained intergrowth of chlorite, sericite, obviously of secondary replacement origin (prob­ quartz and more occasionally carbonate minerals. ably chertified chalk and chertificd calcarenite). The only member of the group of the feldspath- ic wackes is AR5052. It is grey, very poorly sorted, with detrital grains up to 5 mm across, consisting 3.2.3 Metamorphic rock types (fig. 3: h) dominantlv of quartz with undulatory extinction. Feldspar grains comprise both sodic plagioclase and Only four samples were available for petro- K-feldspars. Plagioclase is typically twinned and in graphical analysis. AR4965 is a low-grade pelitic some instances altered to sericite. Minor detrital schist. The typical assemblage of this pale green elements include micas (mostly muscovite flakes), schistose rock is chlorite-muscovite-quartz, with opaque substances and rare zircon. The matrix is albite, opaques, calcitc, and both tourmaline and built by an aggregate of quartz, sericite and chlorite. zircon as accessory minerals. AR4982 is a white metaquartzitic rock consisting of a granoblastic- polygonal aggregate of quartz combined with sub­ Carbonate rocks ordinate (chloritized) red-brown biotite, muscovite, microcline, albite, opaques, apatite and zircon. The Three types have been recognized: calcilutites plagioclases show incipient sericitization whereas (AR4981, AR4983, AR4985, AR5086, AR5092, microcline is always unaltered. Biotite may carry AR5093, AR5096, AR5097 and AR5098), biocal- minute needle-like rutile crystals ('sagenite'). carenites (AR5099) and dolostone (AR5067). AR4987 is another pelitic schist. It contains The calcilutites listed above arc petrographic- sparse small garnet porphyroblasts, crowded with ally similar and creamy in hand specimen. They quartz inclusions, in an assemblage of quartz, un- consist of a cryptocrystalline groundmass of micrite twinned but sericitized albite, (strongly chloritiz­ in which occur randomly scattered globular tests ed) red-brown biotite, muscovite, with apatite and of pelagic (?) micro-organisms with internal micro- zircon as die commonest accessories. Some biotite sparite filling, angular silt-sized grains of detrital crystals are also sagenite-bearing. AR5047, finally, quartz and some opaque substances, including pyrite. is a poorly sorted subfeldspathic arenite of low meta­ Mica flakes are very rare. The non-carbonate con­ morphic grade. The principal constituents of the stituents are volumetrically unimportant. In one rock are quartz and less frequently twinned albite sample (AR4983) the detrital quartz fraction reaches and K-feldspars. The foliation is marked by thin 10 to 20 % of the rock volume whereas in another bands of chlorite, muscovite and (rare) brown bi­ (AR4985) the micro-organisms build about a third otite. Accessory minerals include calcite, zircon, of the rock mass. apatite and sphene. The analysed biocalcarenite AR5099 is yellow­ ish white to creamy and distinctly bedded. The abundant biodasts, displaying a vast spectrum of 4 Provenance shapes and sizes (up to 2.5 mm across), are set in an interstitial sparite cement. They are entirely com­ As die analysed stones probably derive from a posed of carbonate minerals. There is no admix­ gravel deposit which was built mainly or partly by ture of detrital quartz grains. pebble- and cobble-sized clasts, a distinction has AR5067 is a very dark brown, finely crystalline to be made between the source of the raw materials dolostone consisting of rounded silt-sized dolom­ of the clasts and that of the gravel. ite particles enclosing rare detrital quartz grains of the silt-size fraction, minute thin muscovite flakes, opaque constituents and shell debris. 4.1 RAW MATERIALS OF THE CLASTS

4.1.1 Igneous rocks Siliceous rocks Alkalic and tholeiitic basalts and their coarse­ In hand specimen the chert samples encount­ grained equivalents (dolerites) are by far the com­ ered at Raversijde (AR4989, AR5088, AR5089, monest igneous rock types amongst the archaeolo­ AR5094 and AR5100) display either pale brown gical finds available for the present study. They are or ver)' pale grey to dark grey hues with a mottled associated with some weakly to moderately evolved appearance. They primarily consist of granular and lavas (hawaiites, mugearites), a rare siliceous differ­ fibrocrystalline aggregates of chalcedony and micro- entiate (quartz trachyte) and a subvolcanic horn­ crystalline quartz with patches occupied by silic­ blende diorite porphyry which from the petrologic

246 Petrology end Provenance of Unworkcd Stone from the Medieval Fishing-Village at Raversijdc

and genetic point of view may be intimately related vinces of Precambrian or Phanerozoic age which to the basaltic samples. As all examined igneous rock are built by rocks having now here alkalic, now samples were subjected to intense mineralogical there tholeiitic affinities are fairly uncommon in changes it is unlikely in our opinion that they derive Western Europe and completely lacking in Belgium from a Quaternary volcanic province. and most of the adjoining countries. It is well known that basalt is the most wide­ It is nevertheless true that there are two areas spread volcanic rock type on earth and forms in within relatively close geographical proximity to diverse crustal settings. Representatives of the con­ the Belgian coast that are typified by alkaline and trasting alkalic and tholeiitic magma series arc found tholeiitic extrusives and intrusives (dykes, sills and world-wide. In continental terrains, rocks of both larger intrusive bodies). Both are located in the suites are generally associated in a hot spot environ­ British Isles (fig. 4: 5). The first area extends from ment or in zones of tectonic tension and rifting the Midland Valley of Scodand to Northern Eng­ (continental rift volcanism). Extensive volcanic pro­ land. Here lavas were poured out in great prof-

5 The British Isles, with indication of the localities and regions mentioned in the present study. De Britse Eilanden met aan­ duiding van dc in de tekst ver­ meide plaats- en strceknamen.

247 P. DE PAEPE & M. PIETERS

usion during different periods of the Palaeozoic formations of North, North-Wcst or South-West Era and their emplacement was accompanied with England, Wales, the Midland Valley and Southern intrusion of vast amounts of igneous material Uplands of Scotland (fig. 4: 5), or, although less (dolerites). The second district corresponds to the probably, Brittany, in France. British Tertian' Volcanic Province8 (BTVP). It is As far as the cherts and the samples of calcilutite restricted mainlv to the Inner Hebrides (from Skye and biocalcarenite are concerned there is plentiful to Mull), Arran, the adjacent Scottish mainland evidence for an origin in the London Basin or Paris (the peninsula of Ardnamurchan) and North-cast Basin. The chertified limestone probably comes Ireland, though extensive north-westerly linear from die Cretaceous chalk, whereas the calcilutites swarms of dvkes belonging to various stages of this and the biocalcarenite are thought to derive from igneous period extend to North Wales and the Jurassic deposits. The source of the dolostone is English Midlands. As the absolute age of the parox­ much less obvious but a provenance in the rock ysmal magmatic phase is quite different for both sequences that yielded the sandstones is certainly areas it is not surprising that the Palaeozoic rocks conceivable. of the Midland Valley of Scotland and Northern England tend to be much more altered than those exposed within the BTVP The latter are known to 4.1.3 Metamorphic rocks date from early Tertiary times (Palaeocene and early Eocene). Without exception all examined metamorphic rocks (schistose grit, metaquartzite and chlorite- muscovite schist) are of sedimentary origin and 4.1.2 Sedimentary rocks result from low-grade regional metamorphic proc­ esses. Similar rocks are e.g. extensively exposed in A reliable determination of possible geological the Precambrian districts situated north of the sources of sedimentary rocks is often problematic Midland Valley of Scotland (including the Gram­ as many of these rocks have commonplace miner­ pian Highlands) (fig. 4: 5) and less frequendy in alogies and textural features. This also applies to Brittany. the sedimentary material recovered from Ravcrsijde. As we have already mentioned, all rudaceous, aren­ aceous, calcareous and siliceous rock samples in­ 4.2 THE GRAVEL vestigated in the framework of the present project are composed essentially of ubiquitous constitu­ The isolated occurrence of die finds within the ents, show little or no diagnostic skeletal grains and site of Raversijde and the morphological charact­ represent rarely clear-cut or exclusive depositional eristics of the individual clasts suggest in our opin­ environments. ion that the stones were brought collectively to the The finding that the thirty-three analysed sed­ settlement after having been picked up in a shore­ imentary rocks display very mixed lithologies - at line environment. In such a sedimentary context, least six different classes of sandstones and three controlled by the dynamics of waves, tides and cur­ classes of limestones have been recognized micro­ rents, clastic particles of any size coming from dif­ scopically - is nevertheless a most interesting feature ferent geological sources mix and finally setde after that allows meaningful speculation. having been abraded and transported by sea With regard to the seventeen rudaceous and currents. arenaceous rocks identified, it was clearly establish­ As the various rock types identified amongst the ed that die greater part of them are not only mincr- clastic particles of the gravel occur in great quant­ alogically, but also texturally immature, as shown ities in the area extending from the Grampian by the abundance of feldspar grains of highly var­ Highlands of Scodand to the English Midlands, iable type and weathering state, the rather coarse­ and in the knowledge that sea currents in this part grained texture with usuallv poorly rounded and of the North Sea move their load by preference in badly sorted clasts, and the frequent presence of an direction of the Channel, it appears that the north­ interstitial detrital matrix. The sandstone fragments eastern or eastern coast of England is the most furthermore display an extraordinary lithological likely and nearest geological source of the stones variety expressing derivation from predominandy under investigation. In the hypothetical case that igneous (both volcanic and subvolcanic), but also the clasts originate from different localities or derive metamorphic and sedimentary terrains. All these in part from a continental alluvial environment, features argue for an origin outside Belgium. some of the stones (especially cherts and limestone For want of a good knowledge of the sedim­ fragments) may also have been collected quite near entary petrography of the sandstone sequences Raversijde. It is well known e.g. that chert is a major cropping out in countries adjacent to Belgium, the constituent of alluvial deposits and also occurs at most likely and nearest source of the studied sand­ different levels within the Tertian' and Cretaceous stone samples from Raversijde seems to be the rock sequences cropping out in Belgium and Lower (Cambrian, Ordovician, Silurian) and Upper northern France. Palaeozoic (Devonian, Carboniferous and Pcnnian) 8 Durant 1989

248 Petrology end Provenance of Unworked Stone from the iMedieval Fishing-Village at Raversijdc

5 Archaeological implications On the other hand, it is known from historical data that Flemish fishermen, in the context of the From the foregoing can be concluded that the herring-fishery, regularly called at ports on the east­ north-eastern or eastern coast of England is the ern coast of the British Isles12 from the 13th cen­ most likely and nearest source of the stones under tury onwards. Especially the ports of Newcastle investigation. They probably arrived at Raversijde upon Tyne, Scarborough, Filey, Great Yarmouth in the course of the 15 th century, although an earlier and Whitby arc mentioned13 (fig. 5). At the end of arrival cannot be excluded. die 15th century the Flemish herring-fleet consist­ 14 The first observation must be that a combined ed probably of about 150 ships . That the fishing- archaeological/petrological study has independ- village of Walraversijde was quite important can be endy from historical sources demonstrated a late deduced from the number of safe-conducts for the medieval, probably a 15th century, link between English herring fishing-waters that the king of En­ the north-eastern/eastern coast of England and gland delivered in 1443. From the 82 safe-con­ Walraversijde. ducts delivered to Flemish fishermen, 13 were des­ 15 That lots of natural stones turn up in the context tined to fishermen from Walraversijde . of a medieval fishing-village can be explained by The Flemish fishermen also participated in the the need for such materials as ballast for ships. In­ pit-coal trade which in late medieval times was deed, even small ships carry important amounts of centred in Newcastle upon Tyne16 (fig. 5). In the ballast to improve the stability of the vessel9. voyage back from the herring fishing-waters, after But besides the use as ballast for ships, stones having sold the fish in English ports17, pit-coal was can also be used as construction material. At shipped to Flanders. Raversijdc e.g. natural stones have been used as The stones examined in this study probably padi-flooring. Some 16th century records from the arrived at Raversijde just because the Flemish fisher­ municipality of , a small town 5 km to the men regularly came to their area of origin for other north-east of Raversijde, mention e.g. several Flem­ reasons. As it is unlikely that natural stones were ish fishermen, a.o. Vincent Verdieux from Walra­ integrated in the commercial network in the area versijde, being paid for bringing in natural stones of origin, they arc highly valuable in tracing ancient (so-called kzyncsteenen') for the construction or re­ commercial routes. The commercial network is in pair of the Ostend harbour-infrastructure10. In the late medieval times already rather complicated and case of Vincent Verdieux, the stones, according to doesn't allow a simple rectilinear relationship be­ the historical source, came from England. It is in­ tween the find spot and the area of origin18. deed much easier to bring in such heavy loads by Apart from this assemblage of natural stones, the sea rather than over land. site of Raversijde also delivered some scarce other It is however unlikely that the local fishermen finds of English origin: an isolated I4th century went to the north-eastern or eastern coast of En­ coin, a few fragments of querns in Purbeck Marble gland just looking for natural stones. Besides, nat­ and of course numerous fragments of pit-coal. ural stones are not at all mentioned as commercial It is hoped that future petrologic research on products in a historical study on the commercial rocks excavated at Raversijde will provide addit­ and political relations between Burgundy and En­ ional information about the patterns of medieval gland in the middle of the 15th century11. contact and trade.

SAMENVATTING

Patrologie en herkomst van onbewerkte stenen Het geanalyseerde gesteentemateriaal bestaat uit het middeleeuws vissersdorp te Raversijde uit 47 magmatische, 33 sedimentaire en 4 meta­ (Stad Oostende, prov. West-Vlaanderen) morfe gesteenten (fig. 3). De aard van heel wat vondsten sluit een herkomst in België en de meeste Op het terrein van het verlaten middeleeuws van de ons omringende landen uit. Daar de stenen 9 waarschijnlijk afkomstig zijn uit een grindpakket Reindersrt-a/. 1986,27. vissersdorp te Raversijde (stad Oostende) werd in 10 Vlietinck 1897, 47. de 15de-ceuwse grachtvulling tussen de gebouwen dient tevens een onderscheid gemaakt te worden 11 Thielemans 1966. I en 10 een concentratie natuursteen aangetroffen tussen het herkomstgebied van de grondstoffen en 12 Coornaert 1976, 76; (fig. I: 2). Het betrof 84 door natuurlijke proces­ dat van de afgeronde stenen. Asaert 1980. sen afgeronde stenen zonder enig spoor van men­ Wat de herkomst van de magmatische steen­ 13 Dcgryse 1972, 141; De- grvse 1983, 164; Degrysc selijke bewerking. De aanwezigheid van een der­ soorten betreft komen twee gebieden, beide op de 1994. gelijke concentratie stenen in een steenarme regio Britse Eilanden gelegen, in aanmerking. Het eer­ 14 Asaert 1980, 134. als de Polders zette aan tot een nauwgezet petro- ste gebied strekt zich uit van de slenk van de Schotse 15 Degryse 1972, 145. logisch onderzoek. Op deze manier was het mo­ laaglanden (de zgn. 'Midland Valley') tot Noord- 16 Degryse 1983, 157. 17 gelijk om de vondsten mineralogisch, petrografisch Engcland (fig. 4: 5). Het tweede valt samen met Asaert 1980, 132. 18 Hillewaert 1988; Ver- en soms chemisch te karakteriseren en hun her- de 'Britse Tertiaire Vulkanische Provincie (BTVP)'. haeghe 1992. komstgebied nader te omschrijven. Deze laatste treft men aan op sommige eilanden

249 P. DE PAEPE & M. PIETERS

van de Binnen-Hebridcn (cm. op Skye en Mull), Engelse Midlands en de stromingen in de Noord­ aan de westkust van Schotland (vooral in de buurt zee hun lading vooral in de richting van het Kanaal van het schiereiland Ardnamurchan), in Ulster en verplaatsen, is de oostkust of noordoostkust van het noordoosten van de Ierse republiek. Engeland het meest voor de hand liggende her- Gezien de weinig specifieke mineralogische en komstgebied van de verzameling stenen die het texturcle kenmerken van de onderzochte sedimen­ voorwerp uitmaken van deze studie. taire steensoorten is het onmogelijk om hun Uit deze gecombineerde archeologisch-petro- preciese herkomst te achterhalen. Het valt echter logische studie kan het bestaan van een laatmiddel­ op dat ze ook in de randgebieden van beide hoger- eeuws, eventueel zelfs een 15de-eeuws, contact tus­ genoemde vulkanische provincies ontsloten zijn. sen Raversijde en de oostkust van de Britse Ook de vier beschikbare metamorfe gesteenten heb­ Eilanden worden afgeleid. Dat natuurstenen op­ ben weinig exclusieve kenmerken maar een her­ duiken in een vissersdorp is te verklaren door een komst in Noord-Schotland, meer in het bijzonder gebruik van dit materiaal als scheepsbalast. Ander­ in de Grampians, behoort hoe dan ook tot de mo­ zijds kan ook niet worden uitgesloten dat de stenen gelijkheden. in een steenarme regio als de Polders als handels­ Het geïsoleerd voorkomen van de onderzochte waar werden beschouwd. Een Oostends 16de- stenenconcentratie enerzijds en de morfologische eeuws document levert hiervan een voorbeeld. kenmerken van de individuele stenen anderzijds Het feit dat dergelijke stenen waarschijnlijk niet suggereren dat deze ter hoogte van een stenige als handelswaar werden beschouwd in hun gebied kustlijn zijn verzameld. Aangezien de bestudeerde van herkomst, verhoogt hun waarde voor het op­ steensoorten massaal voorkomen in een zone die sporen en in kaart brengen van vroegere handels­ zich uitstrekt van de Schotse Grampians tot de routes.

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VAN HENDE J. 1976: Chemisch onderzoek van silikaat- VERHULST A. 1964: Het landschap in Vlaanderen in gesteenten en mineralen. Universiteit Gent, unpubl­ historisch perspectief, Antwerpen. ished report. VLIETINCK E. 1889: Walraversijde. Een gewezen vis- VERHAEGHE F. 1992: Ceramiekverspreiding en handel schersdorp op de Vlaamsche kust, Brugge. in de middeleeuwen: interpretatie en problemen. In: Teksten van lezingen gehouden tijdens het symposium VLIETINCK E. 1897: Het Oude Oostende en Zijne 'Handel, handelsplaatsen en handelswaar vanaf de Driejarige Belegering (1601-1604), Oostende. Vroege Middeleeuwen in de Lage Landen' te Rotterdam van 2 t/m 3 november 1990, Rotterdam Papers VII, WALKER F. 1935: The late Palaeozoic quartz- 85-116. dolerites and tholeiites of Scodand, Mineralogical Magazine 24, 131-159.

251