Microfacies controls on weathering of carbonate building stones ...

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Microfacies controls on weathering of carbonate building stones: Devonian (northern Sauerland, Germany). Authors; Authors and affiliations. Andreas May.
FACIES

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PI. 37-39

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2 Tab. ERLANGEN 1994

Microfacies Controls on Weathering of Carbonate Building Stones: Devonian (Northern Sauerland, Germany) Andreas May, Menster KEYWORDS: APPLIED FACIES ANALYSIS - CARBONATE BUILDING STONES - WEATHERING RESISTANCE AND DURABILITY - LIMESTONE TURBIDITES - MICROFACIES - MICROPALEONTOLOGY (FORAMINIFERA - CALCAREOUS ALGAE) - SAUERLAND (GERMANY) - DEVONIAN (GIVETIAN/FRASNIAN) CONTENTS Summary 1 Aim of the investigation 2 Material and methods 2.1 Material 2.1.1 Building stones: St.Pankratius church, Eslohe-Reiste 2.1.2 Outcrops 2.2 Methods 2.2.1 Macroscopic weathering criteria: 'Fabric index' 2.2.2 Laboratory data: Porosity, water saturation, insoluble residue 2.2.3 Microfacies and micropaleontology 3 The Beisinghausen Limestone: 4 Microfacies 4.1 Microfacies types 4.2 Diagenetic data 5 Facies-diagnostic microfossils 5.1 Foraminifera 5.2 Calcisphaeres 5.3 Calcareous algae 5.4 Microproblematica 6 Facies interpretation 6.1 Depositional pattern: Proximal turbidites 6.2 Provenance of the turbidite material: Reef lagoon, reef and upper slope 7 Weathering resistance and durability: Comparison of macroscopic data, physical parameter and microfacies 8 Significance of applied microfacies analysis to limestone exploitation References

SUMMARY The Beisinghausen Limestone (Upper Givetian to Frasnian) in the Eslohe-Reiste area (northern Sauerland), used in the past as building stone, corresponds to proximal carbonate turbidites which have been derived from the Attendorn-Elspe 'reef complex. The particles of this allodapic limestone originated in different parts of the carbonate complex as shown by facies-diagnostic microfossils (foraminifera, calcisphaeres, calcareous algae, microproblematica). The fossils as well as the other dominating grain types (lumps, peloids) point to source areas located within lagoonal and slope environments. Reef-derived material is rare.

The turbidites exhibit four microfacies types, differentiated by composition and size of the grains as well as by micrite content and corresponding to the common vertical and lateral textural variation of limestone turbidites. These MF types were recognized in outcrops as well as from building stones used in building the St.Pankratius church in Eslohe-Reiste (northern Sauerland) in 1849 and in the renovation of the church in 1963/64. The comparison of microfacies and the degree of the des~uction of 'old' and 'new' building stones by weathering (macroscopically described by the 'Fabric Index': Product of the 'Rock Destruction Risk' and the 'Rock Preparation Destruction Degree') show s that intrabioclastic rudstones (MF type 1) and bioclastic grainstones (MF type 2), both characterizing the basal parts of the turbidite beds, are more resistant to weathering destruction originating from freezing and thawing than packstones (MF type 4). Weathering of micritic facies types (e.g., MF 4) is more intensive due to the stronger development of joint systems affecting not only the surface of the building stones but the entire dimension stone. Porosity or the existence and amount of stylolites seem to have had no significant impact on the weathering of the building stones studied.The stronger weathering of building stones used in the original construction of the church as compared with the stones applied in this century is caused by the greater time interval available for mechanical weathering connected with freezing and thawing. The consideration of microfacies of limestone turbidites should facilitate the exploitation of weathering-resistant carbonate building stones.

1 AIM OF T H E INVESTIGATION Physical and chemical properties and uses of limestones are controlled by sedimentary as well as by diagenetic processes reflected by the microfacies. However, investigations focused on the relationships between microfacies and geotechnical properties are rare (e.g., SC~ULZE, 1975). The present study compares weathering potential and

Address: Dr. A. May, Lehrstuhl f'dr Allgemeine und Angewandte Geologie, Geologisch-Pal~ontologisches Institut der Westfgdischen Wilhelms-Universit~t MUnster, Corrensslral3e 24, D-48149 Mtinster; Fax: Germany-(0)251-83-2090

194 predominantly clastic sediments of Eifelian to early Givetian age, overlain by the Upper Givetian to Lower Frasnian Beisinghausen Limestone. These well-bedded limestones have long been used as local building stones. 2.1.1 Building stones: St.Pankratius church, Eslohe-Reiste

'

Meschede 9

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9 Elspe Attendorn Fig. 1. Geographical location of the study area and localities mentioned in text. microfacies of a Devonian limestone used as building stone. The stones were utilized as dimension stones for the revetment of a church built in the last century. Some stones of the original construction were replaced in this century because of strong weathering effects. But even the 'new' stones were subject to disintegration primarily caused by freezing. The renovation of the church, starting in 1992, offered the possibility of comparing weathering intensity of the 'old' and the 'new' stones. The building stones were quarried in a local quarry. Samples from this quarry and another locality exhibit microfacies data, necessary for understanding lithological variability and the depositional pattern of the carbonate rock corresponding toproximal limestone turbidites. Microfossils, occurring within the different microfacies types of the turbidite, give an indication to the depositional facies of the shallow-marine area shedding sediment into the basin.

2 M A T E R I A L AND METHODS

2.1 Material The study area (Fig. 1) is situated in northwestern Germany, in the northern part of the Sauerland region. Near Eslohe-Reiste the Devonian sequence is characterized by

The St. Pankratius church, built in 1849, in Reiste (map sheet 4715 Eslohe, R3447050 H5681235), consists almost completely of Beisinghausen Limestone except for the plinths and portals, which are made of sandstone. The surface of the building stones exhibits only slight weathering effects, but many dimension stones display distinct joints, causing destruction and chipping as well as wet areas within the church interior. As a consequence of this serious damage, the outer wall of the double-stressed skin wall construction was demolished and a new outer wall built. During this renovation in 1992, thirty samples were taken from the southwesterly exposed front of the tower, 18 to 20 m above the floor. Twenty building stones ('old' building stones, P 1) had been subject to weathering since 1849. Ten stones from the edge of the tower, added to the wall in 1963/64 and characterized by sharper and deeper working traces, show the more recent weathering ('new' building stones, P 2). All building stones were studied in thin-sections (P 1 to P 30). 2.1.2 Outcrops Today, the Beisinghausen Limestone is exposed in two quarries about 1 km south of Reiste or almost 1 km east of Beisinghausen (Fig. 1): (1) Quarry near the street (map sheet 4715 Eslohe; R 3447650, H 5680400): In the uppermost part of the western wall of the quarry (cf. GAuaLrrz 1967, Fig. 11; uppermost part of the right profile) four meters of grey, medium- to thickbedded limestones dipping southeast are exposed. The beds are massive, showing no significant internal variations in grain size. The thickness of the beds varies between 13 and 90 cm, depending on weathering intensity. Samples R1 to R5. Age: Frasnian. Higher part of the Lower asymmetricuszone to the boundary between the Middle to Upper asymmetricus zone (GAu6taTZ 1967:23). (2) Another quarry (map sheet 4715 Eslohe; R 3447500, H 5680380) is located in the forest west of locality 1. All the building stones used for the St. Pankratius church came from this quarry. Seven meters of horizontally lying limestones, in places with up to 2 cm thick intercalations of marls, are exposed in the steep southeastern wall (see Gaucen'z 1%7: Fig. 11). The limestones are well-bedded. Black chert nodules may occur in some beds. Bed thickness varies between 4 and 70 cm. Very thin bedding structures are visible only in thin-sections.The frequent occurrence of graded bedding, w a w bedding planes, the strongly varying thickness and local wedging of the beds as well as the occurrence of chert layers characterize the beds as limestone turbidites (cf. MeascmmR 1964; E u m 1991). Distinct joints as well as large sparite-filled fissures are common.

195 Age: "Lower asymmetricus zone" (cf. GAUGLrI~1967: 23); lowermost and Lower asymmetricus zone orfalsiovalis and transitans zone (cf. ZmCLER & SANDBERO 1990) corresponding to the uppermost Givetian and lowermost Frasnian (cf. ZIECLeR& KLAPr'ER1985; ZIEGLER• WERNER 1985). Samples R6 to R13 were taken from the lower 3.5 m of the section. 2.2 Methods

The building stone samples were studied with regard to (1) the macroscopic features characterizing the degree of weathering, (2) physical data describing porosity and water saturation and compositional data (amount of insoluble residue) as well as (3) microfacies types and (4) microfossils. 2.2.1 Macroscopic weathering criteria: Fabric index Because the whole building stone is affected by weathering processes and not just the exposed surface, classifications focussed on weathering criteria of rock surfaces (e.g., KtWPER& PISSART1974, GRIMM& VOLga.1983, JAer,rES & COOKE1987, LtaCAS1990, DOPPENBECKER& FITZNER1991) cannot be used. In addition, most classifications do not deal with carbonate rocks but rather with sandstones (HIRsCHWALD 1911, GRIMM1986, MmWALD1987, MEISEL1988, FIIR~R & KOWNATZKI1989, 1991, EtCKELBERGet al. 1990, HILBERT 1991). 'Old' and 'new' (P 1 and P 2) building stones of the St.Pankratius church differ in the preservation of kerb traces, which are more clearly visible on the surface ofP 2 samples than on the surface ofP I samples which are smooth and exhibit only faint working traces. More seriuous than weathering decay of the rock surface is weathering caused by joints which affect the internal structure of the boulder stones and, consequently, security and stability of the walls. In order to describe the intensity of the damage caused by joints a 'Fabric Index' (FI) is used, defined as the product of the 'Rock Destruction Risk' (RDR) times the 'Rock Preparation Destruction Degree' (RPDD). The RDR is estimated, taking into account the occurrence and frequency of joints within the boulder stones. Category 1 is used for just quarried stones. Categories 2 to 6 describe the spectrum of the disintegration shown by the building stone exposed to weathering: Category 2 - low destruction potential without danger of disintegration; category 3 - low destruction potential with sligh flyendangered stones; categories 3 to 6 - increasing destruction potential and danger of disintegration. Category 6 comprises weathering exposed stones which are completely disintegrated. The RPDD is a measure derived from the degree of destruction of the building stones caused by the production of test cubes from the center of the boulder stones. The RPDD ranges from 1 (no damage during sawing and shaping) to 2 (slight damage: destruction of the sample into two or three pieces while sawing or breakage of one test cube), 3 (moderate damage:destruction of the sample into several

parts while sawing or breakage of several test cubes or both destruction types of category 2 occur together) to 4 including totally disintegrated samples. The Fabric Index increases with the intensity of the destruction of the building stone. Building stones exhibit FI values between 2 (no visible damage) to 24 (extremely strong damage). Building stones of the sampling group P 1 used in the original construction of the church and exposed to weathering since 1849 have distinctly more joints and, therefore, significantly higher Fabric Indices than building stones of the sampling group P 2 (see Table 1). The investigation of the building stones from the church in Reiste was facilitated by the experience the author gained while studying samples from the Triassic Trochitenkalk (Upper Muschelkalk) of Bielefeld and from the Wellenkalk (Lower Muschelkalk) of OsnabriJck (MAy, in press). 2.2.2 Laboratory data: Porosity, water saturation, insoluble residue Porosity as well as water absorption and saturation are important physical parameters controlling differences in weathering potential, especially sensitivity to freezing (GRIMM,1990). Parameters measured include (1) dry apparent density (using method RE/DIN 52102 1988:3-4), (2) cold water absorption measured by storing the sample in water for 24 hours at room temperature under atmospheric pressure (cf. Ross et al. 1991: 103), (3) effective porosity (measured by the water absorption after 5 hours of storing in boiling water) as well as (4) the Schurecht ratio, (quotient of cold water absorption and effectiveporosity; see ASTM standards, cf. NmSEL& SC~Mr,~ELWrrz1982:11-13; MARUSIN1985:674). The Schurecht ratio is quite comparable to the saturation coefficient of DIN 52103/1988. The insoluble residue was determined by dissolution in hydrochloric acid. 2.2.3 Microfacies and micropaleontology Microfacies types as well the microfossils, recognizable in thin-sections, were studied in thin-sections of building stone samples as well as in samples from the outcrops of the Beisinghausen Limestone. Microfacies and microfossils are very similar in outcrop and building stone samples.

Microfacies type 1 2 2 3 4 4

Sampling Number unit P1 P1 P2 P1 P1 P2

1 11 9 3 5 1

Fabric Index Min. Max. Average 2 2 4 2

2 12 4 12 15 4

5.7 2.6 7.3 8.4

Tab. 1. Relationship between the degree of weathering and microfacies types of the BeisinghausenLimestone of the church in Reiste. Note the differences in the fabric index (describing the weathering intensity) between 'old' (1849, P1) and 'new' (1963/64, P 2) building stones.

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from 0.1 mm to more than 30 mm (median O 2 mm). The particles are cemented by coarse, blocky sparite. Micritic matrix is absent. The Beisinghausen Limestone is a fine- to mediumSkeletal grains are represented by echinoderms (pregrained bioclastic limestone of Middle to Upper Devonian dominantly crinoid columnals). Fragments of reef-builders age, rich in crinoids and various microfossils. Gross compo(mostly Amphipora and indeterminable stromatoporoids, sition and grain size spectrum is comparable with those of some tabulate corals and bryozoans) are frequent; brachiopod other'crinoid limestones' used as building stones (cf. GmMM, fragments are present.Some bioclasts exhibit micrite 1990). The exceptiona/ly high microfossil content offers the envelopes and microborings. Intraclasts may be very large possibility of studying distributional patterns of foraminifera (more than 30 mm in length); they are bioclastic wacke- to and algae in Middle and Upper Devonian reef and shelf packstones or fine-grained grainstones (MF 3). Larger carbonates. Knowledge of these groups is scanty (see FLt~GEL intraclasts are subangular, other particles are predominantly & HOTZL1971; N E ~ et al. 1975; TsmN 1979; ZtmALOVA angular. Sorting is very poor in samples with predominant 1981a, b; FRIAKOVA& ZtlKALOVA1986; MAMWr& PREAT intraclasts (e.g., P 15, PI. 37/1). In the better sorted sample 1987; VACHARD1988; HLhDmet al. 1989, 1991). The same R 8 (Pl. 38/1) reef-builder fragments and echinoderms is true of microfacies studies dealing with Devonian dominate; intergranular voids are filled in places with graded reef-debris carbonates of the Rhenish Massif (MEIsCHNER carbonate sand and silt. Peloids are very rare. 1964; Ka~s 1974; STgrrzxE 1989, 1990; Mhcm~ 1990; Generally, MF 1 is overlain by MF 2 exhibiting grading Ct~USENet al. 1991). which is more distinct in large hand specimens than in thinIn the area northeast of the Attendorn-Elspe Synclinsections. orium, the Beisinghausen Limestone overlies sandy-siltyMaterial: One building stone sample, another sample clayish sediments of Eifelian to early Givetian age (M~ER from the quarry outcrop 2. in EBERT & M I . ~ R 1973:93-100). Because the time inComparable microfacies types: a) Fore-reef facies: volved in the deposition of the Beisinghausen Limestone 'grobkonglomeratische B/inke' (EB~aT& M~t~R 1973:101comprises the interval between the Upper varcus zone 102), 'arenitische Korallen-S tromatoporen-Fazies' (Saaua-za~ (Givetian) and the boundary Middle/Upper asymmetricus 1989:89, PI. 3/1-2; 1990:271, P1.3/1-2), 'Crinoiden-S tromazone (Frasnian; see GAUCHTZ1967:23; Mr.~_~Rin EBEaT& toporen-Floatstones und -Grainstones' (MAcm~ 1990: 55, Mt~t~R 1973: 105. Now: boundary between punctata and PI. 3/D, 4/A). b) Lagoonal Massenkalk: Rudstones (MAY Early hassi zone, see Zm~t~R & SAr~B~G 1990), deposition 1987:57). of the Beisinghausen Limestone started somewhat later than the development of reefs ('Massenkalk') in the northwestern MF 2 Bioclastic grainstone Sauerland (MAY 1993:11-13) and in the Attendom-Elspe (Plates 37/2, 38/2, 39/3, 9) reef complex (GwosDz 1972:16; M ~ R in EBERT& M0U~R Grainstone consisting of bioclasts, lumps, peloids and 1973:83). intraclasts. Size of the particles 0.08-1.3 mm. A few samples exhibit an indistinct lamination (3-12 mm thick) made of 4 MICROFACIES alternating coarser and finer layers with faint boundaries. 4.1 Microfacies types Particles: Four microfacies types, differentiated by particle types, -- Fossils: Echinoderm remains, mostly crinoid columnals fossils and depositional texture, were recognized in the (frequen0; brachiopods,pelecypods, tabulate corals, stromatobuilding stone samples as well as in samples from the poroids, and bryozoans (common). Calcisphaeres are outcrops. The microfacies types are compared with Devonian frequent, represented by Radiosphaera sp. (common) and MF types described from lagoonal, platform, reef and slope non-radiosphaerid calcisphaeres (common). Other environments. Comparative data were taken from the litera- microfossils include: multi-chambered foraminifera (very ture on turbidites as well as lagoonal limestones. rare), Parathurammina ex gr. dagmarae Sut~YS~,~ov 1945 (relatively rare), Irregularina sp. (relatively rare), VicineMF 1 Poorly sorted bioclast/intraclast rudstone sphaera sp. (locally abundant), Flabellia ufensis SmYVsKY (Plates 37/1, 38/1) 1973 (relatively rare), Vermiporella myna WghY 1967 (rare), Microfacies type 1 corresponds to poorly sorted rudstones indeterminable fragments of calcareous algae (rare), with particles (bioclasts and in~'aclasts) ranging in length Moravammina sp. (relatively rare),Jansaella ridingi MA~-r 3 THE B E I S I N G H A U S E N LIMESTONE:

GEOLOGICAL FRAMEWORK

Plate Fig. 1. Fig. 2. Fig. 3. Fig. 4.

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Microfacies types of the Givetian to Frasnian Beisinghausen Limestone from Eslohe-Reiste, Sauerland, Germany Microfacies type 1. Intraclastic rudstone overlain by coarse-grained variety of microfacies type 2. Sample P15. x4 Coarse-grained variety of microfacies type 2. Bioclastic grainstone. Sample P1. x 8 Microfacies type 3. Fine-grained peloidal grainstone. Sample P13. x 8 Microfacies type 4. Bioclastic packstone. Sample P6. x 8

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& Rotrx 1975 (rare), Proninella sp. (rare), ostracod shells (rare), and tentaculites (rare, only in sample P 18 frequent, PI. 38/2). -- Intraclasts, consisting of bioclastic wackestones and other micritic limestones are common in coarse-grained grainstones. -- Lumps are fi'equent; they are represented by rounded, + irregular micrite grains with sparitic spots. Some lumps probably are micritized grapestones, some micritized bioclasts (cf.microfacies type 3). A few lumps correspond to fragmentation, boring and micritization ofRenalcis (Pl. 39/ 9). Another possible source for the lumps are fore-reef sediments reworked by turbidity currents (EBZRt~ 1991: 341). -- Peloids. Fine-grained grainstones especially contain abundant irregularly rounded, micritic particles with sparry spots (P1.39/3). They are too small for micritized bioclasts, lumps or intraclasts, but too large to be "pseudopellets" (FXFmazus et al. 1974). The samples P 1 (PI. 37/2) and P 28 (PI. 38/2) represent end members of a continuous microfacies spectrum characterized by + loosely packed particles, frequent echinoderms, absence of micrite and occurrence of blocky cement in all of the samples. P1 P28 Most frequent particle type echinoderms peloids Grainsize (median) 0.45 rnm 0.25 mrn Sorting poor moderate angular to sub- angularto Rounding angular well-rounded In several thin-sections a continuous transition into MF 4 is visible. Material: 20 thin-sections, building stones of the church; 2 samples, outcrop at the street; 3 samples, quarry 2. Comparable microfacies types: a) Fore-reef: 'light-gray crinoid-brachiopod facies' (K~Bs (1974:198, Fig. 22-6); 'komponentenarme Arenitfazies' (STmTZ~ 1989: 89-90, PI. 3/ 4; 1990: 272,P1. 3/4).b)Open-marine shallow water: 'microfacies type 2' (Pratt & Mar~m-r 1989:51-52, P1. 2). c) Lagoonal 'Massenkalk': Grainstones (MAY 1987:56-57, Fig. 3).

Plate Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig. 8 Fig. 9. Fig. 10. Fig. 11.

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MF 3 Fine-grained peloidal grainstone (Plate 37/3) The microfacies is commonly characterized by subangular, well-sorted particles (diameter 0.05-0.7 mm; median 0.15 ram). Sorting is better than in microfacies type 2. Lamination similar to MF 2 may occur. Intergranular voids are filled with blocky sparite_ The boundary between MF 2 and MF 3 is gradual or corresponds to a distinct erosional surface. Lumps and peloids are more frequent than bioclasts. Because of a gradual morphological transition from lumps and peloids, the particles may be interpreted as bahamite peloids (FLt~L 1982: 125,134-135). Intraclasts (bioclastic micrites) are rare. Bioclasts are predominantly echinoderms; shells and other bioclasts are subordinate. Calcisphaeres occur with different frequencies.Vicinesphaera sp. may be abundant. MF 3 differs from the fine-grained varieties of MF 2 by a higher frequency of peloids and lumps. Material: 3 thin-sections from the building stones, church; 1 sample from the quarry outcrop 2. Comparable microfacies types: See MF 2. MF 4 Bioclastic packstone (Plate 37/4) Packstones consisting of angular torounded, moderately densely to densely-packed and poorly to well-sorted particles (t210.08-1.4 mm, median 0.27-0.30 mm). Intergranular voids are partially filled by micrite. Lumps and peloids are not always distinguishable because of the dense packing and the micritic matrix. Bioclasts are presented by echinoderms, a few shells and bryozoans. Calcisphaeres and Vicinesphaerasp. may be frequent. Other foraminifera and Vermiporella myna Wru, Y 1967 are rare. Tentaculites are rare to common, ostracods are rare. 80-90 % of the particles consist of echinoderms, lumps, and peloids. Gradual transitions between MF4 and MF2 are common. Material: 6 thin-sections, building stones of the church; 6 samples from the outcrop at the street: 3 samples from the quarry outcrop 2. Comparable microfacies types: a) Fore-reef: 'schwach

Microfacies and microfossils of the Givetian to Frasnian Beisinghausen Limestone from Eslohe-Reiste (Sauerland, Germany) Microfacies type 1. Bioclastic rudstone. Note the graded sediment in interparticle voids. Sample R8. x 8 Fine-grained variety of microfacies type 2. Longitudinal section ofa tentaculite (bottom). Sample P28. x 20 Longitudinal section of Moravammina sp. Sample P28. x 30 Several specimens ofMoravammina sp. Sample P23. x 10 Nanicelta sp. Longitudinal section. Sample P23. x 75 Parathuramminites stellata (LIPINA1950). Sample P20. x 100 Parathurammina ex gr. dagmaraeStrcEV~OV 1945. Sample P1. x 100 Parathurammina ex gr. dagmarae Sta~v~e~Nov 1945. Sample P18. x 100 Multiseptida sp. Cross section. Sample P30. x 75 Several Irregularina sp. (sections of large irregularly shaped tests) and several Vicinesphaera sp. (sections of small globular tests). Sample P28. x 20 Radiosphaera sp. Sample R11. x 100

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ausgewaschene Crinoidenfazies' (SavaTZKE1989:89, PI. 3/3; 1990: 271-272, PI. 3/3). b) Platform slope or shelf slope: 'Microfacies-Association I' (HLAOIL 1986: 6; 1988: 612); 'fine-grained intraclastic-bioclastic Grainstone/Packstone' (HEaam & B~,~Dm~1992: 250-251, PI. 50-51). MF 4 corresponds to the Standard Microfacies Type 4 (bioclastic/ lithoclastic packstone) (cf. WILSON1975:64). 4.2 Diagenetic data

Staining with potassium ferricyanide III and Alizarin red-S (Ft~crrrBAtrr~ & Racm~R 1988:241) indicates that the particles as well as the micritic matrix consist of (_+ non-ferroan) calcite to Fe-I-calcite. The blocky cement has the same composition except for the rare occurrence of Fe-II-calcite. Syntaxial overgrowth on echinoderm grains is frequent. These syntaxial cements often have a lower iron content than the blocky cements, possibly indicating an early diagenetic cementation (cf. SCn~rZIDER 1977:31). Crystal diminution resulting in the formation of fine-crystalline and dull crystals is common. In areas displaying intensive crystal diminuation, irregularly distributed fine-grained (crystal size 0.005-0.05 mm, maximum 0.4 mm) ferroan dolomite occurs. Patchy silicification and idiomorphic quartz-crystals with a length of 0.03-0.4 mm (sometimes replaced by dolomite) are common in areas displaying crystal diminution. Micritic particles and the matrix are more frequently silicified than the sparry cement. Silicification and dolomitization is strong in the MF 4 as compared with the other microfacies types. Many samples exhibit several generations of spar-filled fissures displacing one another. Most of the calcite veins are younger than the silicification, because authigenic quartz replacing the sparry calcite within the fissures is rare. The sparry cements of the later formed fissures are higher in iron (even Fe-III-calcite) than earlier formed fissures. The calcite veins are older than the occasional stylolites which intersect the fissures. 5 FACIES-DIAGNOSTIC MICROFOSSILS The Beisinghausen Limestone - especially MF 2 - contains many microfossils which were studied in the building Plate Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. Fig. 7. Fig. 8. Fig. 9. Fig. 10.

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stone samples P 1 - P 30 and from samples R 6 - R 13 (quarry outcrop 2). Some of these fossils are facies-diagnostic and can be used in the reconstruction of the source area of the turbidites. All microfossils are uppermost Givetian to lowermost Frasnian in age. The systematic position of many of these microfossils is not known. LOEBLICH• TAPPAN(1988), for example included as foraminifera all the genera regarded in this paper as unilocular foraminifera, whereas Too~mY & MAMET (1979:190) and VAO~P,O (1991 ) excluded most of the taxa from the foraminifera. Moravammina, commonly interpreted as a foraminifera, and Kamaena, usually interpreted as green alga, are included within the class Algospongia TERriER & VACaARD1977 by VACHARD(1991). The systematic position of the calcisphaeres (+ spherical single-chambered tests without apertures), common in shallow-marine, often lagoonal Devonian carbonates, is also uncertain (FLt3GEL& HOTZL1971; Toothy & MAME'r1979; FLt3CEL1982; MAr~m-r& PREAT1987; MAME71991 ). Different taxonomic assignment, however, may lead to contrasting paleoenvironmental interpretations. An attribution of calcisphaeres and other single-chambered microfossils to the chlorophyte Eovolvox (see KAZr~ERCZAK1976), would point to an interpretation of the carbonates as deposits of eutrophic freshwater and brackish water lakes. In contrast, if the calcisphaeres are regarded as reproduction cysts of dasycladacean algae (WRAY 1972; MARSZALEK 1975; ARMSTRON~ & MA~'r 1977), + normal marine salinities could be inferrred (Rotm 1985; BERCZR& KAEVER1992). 5.1 Foraminifera

Multi-chambered tbraminifera are rare. Spirally-coiled multi-chambered tests belong to the genusNanicella HEr~EST 1935 (PI. 38/5), known with several species from the Early Devonian of Tunesia (VAcrL~RD& MASSA1989) as well as from the Givetian and Frasnian of U.S.A, Canada, France, Belgium, Poland, the Czech Republic, the Urals, Siberia, and Afghanistan (see LOEBLIr & TAPPAN 1964; TOOMEYet al. 1970; MENNZR& REITLINGER1971; NEUMANNet al. 1975; TSIEN 1979; FRaAKOVA& ZtmALOVA1986; GALLEet al. 1988; VACHARD1988; HLADmet al. 1991; VACHAP,O 1993). Uniserial, elongated tests are also rare. A transversal

Microfossils of the Givetian to Frasnian Beisinghausen Limestone from Eslohe-Reiste (Sauerland, Germany)

Proninelta sp. Two longitudinal sections (top left and bottom right). Sample PI0. x 40 Flabellia ufensis Smrvs~:v 1973. Cross section. Sample P2. x 40 Several Vicinesphaera sp. Grainstone with lumps and peloids, microfacies type 2. Sample P2. x 40 Calcisphaere, type 1 sensu FLO~EL& H0ZZL(1971). Sample P4. x 100 Calcisphaere, type 2 sensu FLt3~EL& HOrZL(1971). Sample P13. x 100 Flabellia ufensis SmrvsKv 1973. Cross section. Sample P2. x 40 Vermiporella myna WRAY 1967 (right) and Eovolutina sp. (arrow). Sample P28. x 40 Fragment of Jansaetta ridingi MAr,m'r & Rotrx t 975, longitudinal section. Sample P28. x 40 Large lump showing Renalcis-like structures (right) together with several smaller lumps and peloids. Grainstone, microfacies type 2. Sample P4. x 20 For comparison with Fig. 9: Renalcis granosus VOLO~DrN1932. Reef-debris limestone, Upper Frasnian of Sumbera, Moravia. x 20

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section of a test (0.3 mm O) shows radial foldings of the inner side of the wall, characteristic ofMultiseptida BYrovA 1952 (P1. 38/9). Thegenus is known from the Frasnian-Famennian of Canada, the Russian platform, Poland and the Czech Republic (Too~mYetal. 1970; N E ~ etal. 1975; Toothy & MAMFr 1979; LO~LICH & TAPPAN 1964; FmAKovA & Z ~ o v A 1986; G~3.~ et al. 1988; Ht~mr et al. 1989). Parathurammina Stn.~C~tANov1945 is represented by a few tests. This genus comprises many species (see Jtr~REV 1961; PROI,r~A 1970; M E ~ R & RzrrLINGZR1971; SALVOVSm',JA 1981; Zur~ovA 1981a, 1981b; V A C ~ 1991). The tests occurring in the Beisinghausen Limestone (P1. 38/7-8) are attributed to Parathurammina ex gr. dagmarae S~MANOV 1945. The specimens show strong similarities with the type species Parathurammina dagmarae S ~ o v 1945 (cf. LoEBuc8 & TAPPAN 1988:191, PIs. 207/18, 207/21) and corresponds to the description of P. dagmarae from the Givetian of the western Sauerland (FL~36~ & HOTZL1971). The Eslohe-Reiste material shows the following dimensions: Maximum diameter of the test 0.29-0.40 mm, wall thickness 0.010-0.020 mm, aperture diameter 0.015-0.030 mm. The wall is microcrystalline. 36 spines with a length of 0.03-0.09 mm were observed. Unilocular tests (diameter 0.15-0.18 mm) of Parathuramminites P o Y ~ o v 1969 (PI. 38/6), characterized by 6-7 hollow, up to 0.08 mm long spines are rare. A distinct aperture is absent. The wall is dark in transmitted light and remarkably thick (0.030-0.045 mm).The material corresponds to P. stellata (Lu,~A 1950) known from the Givetian and Frasnian of France, the Russian platform and Siberia (see V A ~ 1988; MEt~R & REITLINGER1971), but not from Germany until now. The unilocular foraminifera Bisphaera elegans VISSAPaONOVA1950 is rare. The test is subsphaerical to bean- shaped, the maximum diameter 0.40-0A8 mm. The single-layered microcrystalline wall has a thickness up to 0.03 mm. The tests correspond well to the description of the species by VA~ (1988, Frasnian of Northern France) as well as to the material from the Middle Devonian Massenkalk of the western Sauerland, assigned by FL~OEL& HOTZL(1971) to Bisphaera sp. cf. grandis LU,tNA 1950. Bisphaera is widely distributed in Givetian and Frasnian shallow-marine carbonates of Eurasia and Canada (FLI2GEL~(~ HOTZL 1971; TOOMEYetal. 1970; NEUMANNetaL 1975; Zur~LOVA 1981b; FmAxovA & ZUKALOVA1986; VACHARD1988; LOEBLICH& TAPPAN 1988; VACHA~ 1993). The genuslrregularina BYKOVA1955 is represented by rather rare single-chambered, irregularly oval, elongate and sometimes strongly lobate tests with a maximum length of 0.6-1.2 mm (PI. 38/10). The 0.010-0.025 mm thick wall is microcrystalline. Irregularina sp. is distinguished from Bisphaera elegans by its well developed aperture and its larger, more irregular tests. Irregularina was described from the Givetian to Lower Carboniferous of the former USSR (Lo~ucH & TJ~'PAN 1988) as well as from the Frasnian of southeastern Poland ( N E ~ et al. 1975) and Moravia (Zur~,t~vA 1981b). One specimen of Eovolutina sp. exhibits an oval test with a diameter of 0.21 mm (P1. 39/7). The outer wall is 0.02-

0.03 mm thick and microcrystalline. The roand proloculus visible in the centre of the test has a microcrystalline wall half as thick as the outer wall. Eovolutina ArcrRoPov 1950 was known only from the Upper Silurian to Famennian of the former USSR until now (LOEBUCH& TAa'PAN1988). The most abundant unilocular foraminifera is Vicinesphaera sp. (PI. 38/10, 39/3) corresponding well to the description by FLf3G~ & H O ~ (1971, Givetian Massenkalk of the western Sauerland). The interior diameter of the tests is 0.06-0.10 ram, the exterior diameter 0.10-0.19 mm, the wall thickness 0.01-0.05 mm thick. The microcrystalline wall is of variable thickness and encloses a spherical cavity. Pores and an aperture are absent. The single-chambered genus Archaesphaera is represented in the Beisinghausen Limestone by only two specimens with an outer diameter of 0.14-0.15 mm and a light, non-porate wall (thickness 0.010-0.015 mm). 5.2 Calcisphaeres

The genus Radiosphaera REn~rNGzR 1957, which has a world-wide distribution, is also common in the Beisinghausen Limestone. The test is characterized by a thick wall (0.03-0.1 mm); the inner diameter of the spherical cavity is 0.1-0.22 mm. The maximum outer diameter reaches 0.22-0.33 mm. With the exception of the microcrystallineinteriorboundary, the coarsely radial-fibrous wall is light gray in transmitted light. The wall of almost all specimens exhibits a ragged outline (P1. 38/11). The specimens correspond very well to the material described by STArCrON(1967), WV,AV (1967), TOO~C~vet al. (1970) and FLOCEL& HOVZL(1971). Non-radiosphaerid calcisphaeres are rather frequent in the thin-sections but are difficult to classify owing to strong changes by micritization and/or diagenesis. The'form types' 1, 2 and 5, distinguished by FLt~GEL& HOT-ZL(1971) were identified. Calcisphaeres grouped within form type 1 comprise spherical tests with an inner diameter of 0.09-0.11 mm and an exterior diameter of 0.13-0.15 mm. The thick (0.020-0.025 mm) one-layered wall is light in transmitted light and pierced by many radially arranged pores (P1.39/4). Plate 39/5 shows a calcisphaere attributed to form type 2 ( exterior diameter 0.38 mm, wall thickness 0,04 mm). Small calcisphaeres (outer diameter 0.15 mm), characterized by a double-layered wall (light inner granular and irregularly defined outer microcrystailine layer) correspond to the form type 5. 5.3 Calcareous algae

Comparable to platform carbonates ('Massenkalk') of the Sauerland (FL~GEL& HOrZL1971; MAY 1988), calcareous algae are rare, reworked spongiostromate crusts extremely rare in the Beisinghausen Limestone. Flabellia ufensis Sra~sKv 1973, described from the Ordovician and Silurian of Canada, the Lower Devonian of the Urals, and the Middle Devonian of the western Sauerland (Smasra 1973; Marcm'r & Roux et al. 1992; MAy 1992), occurs occasionally (PI. 39/2, 6). The material from Reiste

203

corresponds highly with the description given by MAy (1992). The transversal section reveals (irregularly) crescent-shaped layers, (0.03-) 0.06-0.08 mm thick and 0.91.3 mm long. The layers may or may not exhibit 2 or 3 thorn-like protuberances on their convex side (cf. PI. 39/2, 6). One layer consists of one row composed of 26-35 cells, which are 0.03-0.06 mm wide. The walls are diagenetically thickened (0.01-0.03 mm). The fossil described from the upper Famennian of Moravia as Vermiporella sp. by I~LVODh & KOSTELYlcEK(1981 :P1.60/1) is a relatively small specimen of Flabellia ufensis. The dasycladacean alga Vermiporella rnyna W~Y 1967 is rare. The best preserved specimen (P1.39/7) is represented by a 1.25 mm long section through an irregularly cylindrical thallus. Outer thallus diameter is 0.4 mm thick, wall thickness 0.02-0.05 mm. Branches are aspondyl, running perpendicularly to the central stem axis. Diameter of the branches 0.015-0.020 mm. Twelve branches occur within a distance of 0.3 mm. VermiporeUa myna has been described from the Frasnian of western Australia (WRAY1967), as well as (as cfform) from the Frasnian of Canada (TooMEyet al. 1970) and Middle Devonian of the Sauerland (FL12GEL& HOTZL1971 ; MAY 1992). 5.4 Microproblematica

8 are: tube diameter 0.12-0.14 mm, wall thickness 0.0200.025 ram, distance between the septa (0.06-) 0.22-0.3 ram. These microfossils were described by Rtt)n~o& J~'~SA(1974, 1976) from the Givetian-Frasnian of Canada and from western Australia, named Jansaella ridingi by ~ & Rotrx (1975). A few of the 'lumps' common in MF 2 and MF 3 seem to presentreworked (and partly micritized) skeletons of Renalcis VOLOODr~1932 (P1.39/9). The identification of the fragments found in the Beisinghausen Limestone is difficult because controversial opinions exist regarding the taxonomic concept ofRenalcis. Rlo~o (1991a; 1991b) and VORONOVA(in VORONOVA& Rt~lONOVh 1976) subdivided the morphologically highly variable group into several genera, wheras MAMZr & Rotm (1983) attributed all forms to the cosmopolitan species Renalcis granosus VOrO(~DIN1932 (Cambrian to Carboniferous). Material collected by the author (PI. 39/ 10) in Upper Frasnian reef-debris limestones of Sumbera north of Brno, Moravia, (cf. G~a..t.E& ~ I L 1991) supports the interpretation given by MAME-r& Rotrx (1983) and also by PONCE'r(1986), Rotrx (1991), MAMET(1991), MA~L'r& BotrLVhIn (1992), and with some restrictions by V A C ~ (1993). Renalcis is frequent, and in places quantitatively dominant, in reef cores of Devonian carbonate complexes of Canada, western Australia, and Belgium (WRAY1967;WRAY PLAYFORD1970; JAMIESON1971;/V[ACHIELSE1972; WRAu 1972; RtDtNO1979; TSIEN1979; MA'ITER1984). Renalcis is also known from the Sauerland (MAy 1988). If parts of the lumps are remains of Renalcis, these 'lumps' would have originated in reef or near-reef areas. For the common typical lumps, however, a source area within lagoonal environments must be assumed.

Rather irregularly formed, nearly straight or slightly curved and seldomly bifurcated tubes with an aperture (outer tube diameter 0.18 to 0.5 mm) belong to Moravammina sp. (P1.38/3-4). The largest tube is 1.9 mm long. Wall thickness varies between 0.02-0.03 mm for the smallest tubes and 0.04-0.07 mm for the largest tubes. The light wall is granular or faintly radial- fibrous. Some of the tubes are subdivided by thin septa. Closely-spaced septa as in Evlania mistiaeni VAO-L~a~I~1988 are absent. Moravammina POKORYV1951 is 6 FACIES INTERPRETATION known from the Emsian to the Frasnian time interval in 6.1 Depositional pattern: Proximal turbidites Europe and Asia (LoEal.SCn& TAPPAN1964; 1988; ME.NNER REITLINGER1971; VACHARD1991, 1993). According to MEISCIU'~IER(1964), GAtJOt_vrz(1967) and Proninella sp, (PI. 39/1) is rare. It is represented by 1.1- EDERet al. (1983) and supported by the microfacies data, the 1.4 mm long fragments of irregularly shaped and slightly Beisinghausen Limestone is of turbiditic origin. The sedimcurved tube-like tests (diameter 0.15-0.25 ram). The 0.02- entological criteria visible in large hand samples (grading, 0.04 mm thick, granular wall appears either dark or light in shale to marl at the base of the bed, overlain by the microfacies transmitted light, depending on the preservation. The tube types 2-4) show that microfacies type 1 is part of a proximal encloses protrusions of the wall forming irregular pillars and limestone turbidite deposited in a high-energy environment septa. A specific determination is not possible because of the from a highly dense turbidity flow (cf. MEISCaYZR1964; poor preservation. Until now PronineUa P,JaTL~GER was MCILREATH& JAMES1984; EINSELE1991; EBERLI1991). A known from the Devonian only from the Givetian-Famennian multiple deposition of older lithified turbidites is indicated of Siberia, Poland and France (MENNER& REITLINGER1971 ; by intraclasts exhibiting the microfacies type 3 within the NEUMANNet al. 1975; VACrIARD1988; LOEBLICH8s TAPPAN turbidite beds. 1988). The vertical succession of the microfacies types {coarseOther rare microproblematica are 0.55-0.85 mm long grained mdstones (MF 1) at the base, overlain by bioclastic fragments of almost straight isolated tubes, subdivided by grainstones (MF 2), and the overlying bioclastic packstones thin septa orientated perpendicularly to the wall. The granu- (MF 4) and/or fine-grained peloidal grainstones (MF 3)} lar wall of the tube is light in transmitted light, and exhibits corresponds to the general pattern visible in allodapic fine (few micrometres sized) dark pores. The 0.01 mm thick limestones (M~scnnER, 1964). The change in water energy septa also consist of granular calcite. A specimen with an is documented by the change of high-energy microfacies outer tube diameter of 0.1-0.12 mm is surrounded by a types (1 and 2) to the low-energy microfacies types 3 and4. 0.015-0.020 mm thick wall, and includes sepia 0.09-0.16 The turbidites have been derived from the Attendornmm apart. The dimensions of the specimen figured in Pl. 39/ EIspe Massenkalk reef complex, situated about 15 km to the

204

southwest of the Beisinghausen Limestone (see GAtJGLn'Z 1967:Fig. 20; EDERet al. 1983: 102). In order to understand the source area and depositional pattern of the turbiditic sediment, the Brilon 'Massenkalk' reef complex should be compared. This reef complex is, similar to the location of the Attendorn-Elspe reef complex (see Iga~Bs 1974; Bba~c_r~-rr~1981; EDERet al. 1983) situated on the northeast to southwest running southern shelf margin of the Old Red Continent. MAY(1987:71 ) and Macmm ( 1990:56) proposed different facies models for the Brilon reef complex, which, however, have two features in common: (1) The lagoonal area is situated on a flat platform and (2) the reef core is located on the upper part of the basinward slope of the carbonate platform. 6. 2 Provenance of the turbidite material: Reef lagoon, reef and upper slope

The spectrum of particles in the Beisinghausen Limestone becomes understandable by using the models proposed for the Attendom-Elspe'Massenkalk' reef complex: A large part of the lumps, many of the peloids as well as the skeletal grains represented by calcisphaeres, foraminifera, and calcareous algae, and probably also some of the reefbuilder debris (Amphipora), were produced within a lagoonal area of the carbonate platform. The micritic intraclasts (bioclastic wackestone) originated partly in the lagoon, partly during the deposition of the turbidites. The abundant echinoderm debris may be derived from the reef core and adjacent crinoid meadows flourishing on the upper fore-reef slope. The amount of sediment which can be interpreted as eroded and transported reef material (some fragmented reef-builder, mainly non-dendroid stromatoporoids, and perhaps the "Renalcis lumps'), is significantly low. Pelagic tentaculites represent the open-marine basinal environment. Grain composition (lumps, peloids, coated grains, Amphipora fragments) and texture of MF 1 and MF 2, characterizing different parts of the proximal turbidite beds, are very similar to those of high-energy shallow-marine carbonates (cf. P~Ax & Ma~m-r 1989). Microfacies type 2 exhibits a mixture of particles derived from lagoonal environments, reef core areas and basinal settings (cf. Ka~BS 1974; B ~ c r ~ 1981). Shallow lagoonal environments as source areas of most of the allochthonous sediment deposited as turbidites are also indicated by facies-controlled organisms: Amphipora is generally regarded as an indicator of a lagoonal environment (cf. JA~soN 1971; K.r~Bs 1974; FLOG'EL& HO'rT~1976; Btmcstu lrE 1981 ; MarnzR 1984; MaY 1988; ISAACSON& GALke 1991). Calcisphaeres as wellasParathurammina,lrregularina, Vicinesphaera, Archaesphaera and Bisphaera were abundant organisms in protected marine shallow-water environments (lagoons, back-reef) during the Middle and Late Devonian (cf. STA~rro~ 1967; Toorcmyet al. 1970; FLt~GEL& HCYr'ZL1971; Macnmts~. 1972; KO,F~S 1974; NEtrs~re~ zr AL. 1975; MA~zr & ~ T 1987; MaY 1988; Pe,EAT& MA~-'r 1989; Rotrx 1991; MAMzr 1991; VACHARD 1993: 65).

Nanicella, Proninella, Vermiporellaand Jansaella are indicators of shallow subtidal environments (cf. JAMIESON1971; RIDn~ & JArqsA 1974, 1976; Pdt~c 1979; Ma~-r & PIn,AT 1987; G,~t~ et al. 1988; MAr~T 1991; MaY 1992). 7 WEATHERING RESISTANCE AND DURABILITY: COMPARISON OF MACROSCOPIC DATA, PHYSICAL PARAMETER AND MICROFACIES

The project aims at a better understanding of carbonate building stones exposed to weathering for different time spans (approximately 143 years and 29 years). In addition, the different weathering durability of one and the same limestone should be discussed as well as possible relationships with microfacies and physical parameters. Various methods, including petrographic and SEM studies, geochemical investigations, porosity and water absorption measurements, and ultrasonic studies of test cubes are commonly used in order to describe parameters explaining differences in the weathering potential of building stones. The application of these methods to Triassic building stones from the Muschelkalk (May, in press), shows that ultrasonic data, scanning electron microscope criteria, and partly also geochemical data were of little value in giving a reasonable explanation of the weathering potential.These methods, therefore,were omitted in the course of the investigation of the Beisinghausen Limestone.Thereis, however, a significant relation between microfacies and weathering: These relationships are shown in Table 1, indicating that variations in the weathering durability of building stones may depend on the original microfacies type. Distinct differences in the Fabric Indices of 'old' and 'new' building stones (P 1 and P 2) representing the same microfacies show that the disintegration during weathering is a) time-controlled and b) that microfacially different building stones exhibit different weathering resistance. Weathering resistance of MF4 (exhibiting a high FI) is low as compared with that of MF 2 (with lower FI). Because MF 4 differs from MF 2 only by the occurrence of micritic matrix, weathering durability seems to be, at least partly, controlled by the amount of micrite. The small disintegration (and low FI) of MF 1 building stones points in the same direction. A higher amount of sparry carbonate cements seems to favour weathering resistance and durability. The absence or existence of laminations and fine bedding may be another factor influencing weathering resistance as shown by samples from the Triassic Wellenkalk (non-bedded building stones exhibit a higher weathering resistance). The samples from the Beisinghausen Limestone indicate no distinct control of weathering durability by the occurrence and frequency of stylolites and of sparite-filled veins or by the particle-size of the grain -, pack- and rudstones. Muschelkalk samples with an effective porosity between 1% and 8 % exhibita decrease in weathering durability (corresponding to increasing Fabric Indices) along with increasing cold water absorption or increasing Schurecht ratios (MAY,in press). Due to the generally low porosity of the Beisinghausen Limestone (Table 2), this trend cannot be

205

Parameter

Sampling Units

Length of the building stones (cm) Height of the building stones (cm) Depth of the building stone (cm) Rock Destruction Risk (RDR) Rock Preparation Destruction Degree (RPDD) Fabric Index Dry apparent density (g/cm3) Cold water absorption (vol.-%) Effective porosity (vol.-%) Schurecht ratio (Cold water absorption: effective porosity) HC1 insoluble residue (%)

P1 P2 P1 P2 Pi P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2 P1 P2

Min. 21 14 15 14 18 12 2 2 1 1 2 2 2.620 2.698 0.28 0.20 0.31 0.21 0.701 0.739 1.73 0.76

recognized in the samples studied. The non-carbonate insoluble residue is another factor influencing weathering resistance and durability of limestones as also shown by the Muschelkalk samples (increasing disintegration along with increasing residue content). A comparable trend is not evident for the Beisinghausen Limestone building stones probably because of the low residue content (see Table 2), Most authors (e.g. WXNKLER1973, AMOROSO& FASSINA 1983, JAYNES & COOKE 1987, ATrEWELL& TAYLOR 1988, SHERWOOD & REDDY 1988, VLEUGELSet al. 1988; LIPFERT 1989, AmES-BARROSetal. 1990) explain the disintegration of carbonate building stones by erosion and destruction processes at the surface caused by air pollution. The disintegration of the Beisinghausen Limestone building stones, in contrast, is caused by joints starting at the surface which are caused by changes in stress (associated with repeated freezing and thawing processes). Widening of the joints is predominantly controlled by frost bursting. Destruction by plants and dissolution are of minor importance as shown by the rather weak changes of the building stone surface. 8 S I G N I F I C A N C E OF A P P L I E D M I C R O F A C I E S ANALYSIS T O L I M E S T O N E E X P L O I T A T I O N The study of the Beisinghausen Limestone demonstrates the importance of micro facies investigations in the exploitation and use of limestones as building stones: The use of carbonate turbidites as building stones is favoured by the differentiation of the beds in distinct separation planes and because of their wide lateral extension. Depending on the palaeogeographic position, the lithologic properties vary

Max. 46 46 36 2l 39 26 5 3 4 2 15 4 2.726 2.710 0.59 0.59 1.46 0.67 0.991 0.985 7.02 2.26

Average 36,3 30.2 20.5 16.8 27.5 17.4 2.9 2.2 2.1 1.3 6.5 2.8 2.697 2.704 0.43 0.43 0.60 0.46 0.909 0.918 3.26 1.60

Tab. 2. Criteria of the building stones (Beisinghausen Limestone); outer wall of the church in Reiste: Dimensions; degree of macroscopically observable desmaction (RDR, RPDD); physical and chemical properties. P 1: Sampling unit (20 samples) consisting of building stones exposed to weathering since 1849. P 2: Building stones (10 samples) exposed to weathering since 1963/64.

with increasing distance from the source area (MmscHNER 1964; EDER et al. 1983). Proximal parts of turbidites, e.g. the Beisinghausen Limestone, are better sites for quarries exploiting building stones because a) the individual beds are thick, b) marly intercalations are rare as compared with distal parts, and c) the micritic microfacies types (less resistant to weathering) may be relatively rare. Exploitation of material suitable for building stone production can be improved by a planned search for those microfacies types exhibiting higher weathering resistance and durability. In the Beisinghausen Limestone example these are the microfacies types 1 and 2 characterizing the basal parts of the turbidite beds. ACKNOWLEDGMENTS I would like to thank Prof. Dr. K. Poll (MOnster) for advice and support, E. W. DOrschetn (Miinster) and his staff - especially R. Metzdorf - for the preparation of the thin-sections, and F.-J. Happe (Meschede) for information and support in the study of the church in Eslohe-Reiste. Dr. J. Hladil (Prag) rendered the collection of comparison material in Moravia. The study was supported by a post-doctoral scholarship (Postdoktorandenstipendium) of the Deutsche Forschungsgemeinschaft. The critical comments of an anonymous reviewer and of Prof. Dr. E. Fltigel (Erlangen) are greatly appreciated. REFERENCES AIRES-BARROS,L., ALVES,L. M.,CARMO, A.M.M., GRACA,R.C.,, MAURICIO,A.S. & RmEmo, M.M. (1990): Weathering and air pollution action on limestones of Jertnimos monastery, Lisbon Portugal. - Mem6rias e Noffcias, Publ. Mus. Lab. Mineral. Geol. Univ. Coimbra, 109, 117-130, 9 Figs., Coimbra -

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Manuscript received October 15, 1993 Revised manuscript accepted January 16, 1994