Microfacies of Carbonate Slope Boulders: Indicator of the Source Area. (Middle Triassic: Mahlknecht Cliff, Western Dolomites). Mikrofazies allochthoner ...
FACIES
25 279-296 Taf. 69-74
3Abb.
1 Tab. ERLANGEN 1991
Microfacies of Carbonate Slope Boulders: Indicator of the Source Area (Middle Triassic: Mahlknecht Cliff, Western Dolomites) Mikrofazies allochthoner Hangkarbonate: Hinweise auf das Liefergebiet (Mitteltrias: Mahlknecht-Wand, Westliche Dolomiten) Rainer Brandner, Innsbruck, Erik FI0gel and Baba Senowbari-Daryan, Erlangen
KEYWORDS:
FACIES ANALYSIS - CARBONATE ROCKS - P A L E O N T O L O G Y - PLATFORM MARGIN PALEOSLOPES - SOUTHERN ALPS (DOLOMITES) - TRIASSIC (LADINIAN) CONTENT
Summary - Riassunto 1 Introduction 2 Locationand geologicalsetting 3 Biotaand facies types 4 Sedimentologicalrole of organisms 5 Conclusion References
SUMMARY
Paleontological and microfacies criteria of limestone boulders occurring within megablocks deposited on clinogonal slopes provide indications of the source area of Middle Triassic allochthonous carbonates exposed in the Mahlknecht cliff, Seiser Aim, Dolomites. Microfacies, biotic composition, a high percentage of low-growing binding and baffling communities (sponges, algae, microproblematica) as well as the remarkable coincidence with distributional patterns observed on other Ladinian paleoslopes indicate a source area characterized by common bioconstructions, which is situated on a subtidal upper and middle foreslope and not at the platform/slope-margin or on the carbonate platforms. RIASSUNTO I megablocchi calcarei del Trias medio affioranti vicino al RiL Molignon (Alpe di Siusi, Dolomiti) sono costituiti di clasti carbonafici risedimentati, l] loro studio ha permesso di formulate un'ipotesi suil'area di alimentazione dei clasti stessi. I daft paleontologici, l'analisi e la distribuzione delle
REEFS
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microfacies, ralta percentuale di organismi "oinding' e' baffling' a basso tenore di crescita) spugne, alghe e microproblematici} indicano una sorgente di alimentazione caratterizzata da biocostruzioni simili a quelle osservate in altrepaleoscarpate ladiniche. In particolare tale sorgentedoveva essere ubicata in ambiente subtidale nella parte media ed alta della scarpata e non al margine piattaforma/scarpata o sulla piattaforma stessa. 1 INTRODUCTION The spectacular scenery of the Dolomites in the Southern Alps is characterized by huge Middle Triassic and Camian carbonate masses sloping via clinoforms into basinal sediments. Statting with the s011classical books by RICHTHOVEN(1860) and MoJsisovlcs (1879) these carbonates were regarded as coral reefs or coral-algal reefs (I_~oNARDI1961, 1967, 1979; L~ONARDI& ROSS11957;ROSS11957,1959a, 1959b). BOSELLn~ & ROSSl(1974) and CRos (1974) replaced the coral-algal reef model by a non-ecologic carbonate buildup model which emphasizes the role of sediment-trapping and binding organisms and of early (freshwater) cementation in the formation of the Ladinian and Catalan carbonates developing at the edge of shallow-water carbonate platforms. Because of the intensive dolomitization of many carbonates the facies and biota of platform margins are usually inferred from gravity-displaced carbonate boulders deposited on the slope or embedded within basinal sediments Most of this data is related to the 'Cipit blocks' derived from Ladinian and Carnian buildups (Bml)LE1979,1981; Bosm.m~ & RossI 1974, FORSlCn & W~arr 1977, HARMS1988, Wm,ro'r 1980, 1982; S ~ 1977, Russo et al. 1991).
Addresses: Dr. R. Brandner, Institut fiir Geologie und Pal~lontologie,Universi~t, Am Innrain, A-6020 Innsbruck; Prof. Dr. E. Fltigel, Dr. B. Senowbari-Daryan, Institut fur Paliiontologie, Universit~t Erlangen-Ntirnberg, Loewenichstra~ 28, D 8520 Erlangen
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Fig. 1. Paleogeographicalposition (after Bosr~J.t.n~11984)and location of the Mahlknecht Cliff. The distribution of the platforms during the Upper Ladinian corresponds to that of the early Ladinian. The Mahlknecht Cliff exposes slope and base-of-slope deposits. Microfacies of Ladinian and Carnian buildups and allochthonous carbonates were studiedin detail by CRos(1974a, 1974b), Fols & GAFrANI(1980), FOIS(1981) and GAZrANIet al. (1981). These data give evidence of (a) the formation of many Ladinian buildups within subtidal and, some buildups within intratidal to subtidal environments (e.g., Latemar), (b) the lack of a rigid biological framework and of an accumulation of oolitic or bioclastic shoals at the boundary between carbonate platforms and foreslopes, (c) rare, if at all subaerial exposure of many Ladinian platform margins (in contrast to late Ladinian and Carnian platforms: BmDI.E 1981, 1984; Russo 1991), (d) intensive synsedimentary submarine cementation, intimately connected with the growth of 'algal crusts' (e) existence of foreslopes gradually dipping towards the basins, resulting in initial slope angles of 25" to 35" for Ladinian 'reefs' (reaching the maximum slope angle at a slope height of approximately 500-600 m; K~rr~R 1990), (f) autochthonous biogenic sedimentation on the upper part of the slope, resulting predominantly in the formation of bafflestones and only a few framestones, and in the middle part of the slope (bafflestone and bindstones). (g) stabilization of platform margins and the upper slope by binding and encrusting organisms. The increase in biogenic carbonate production is regarded as one of the major factors responsible for the growth of the buildups and, in turn, for the allochthonous sedimentation on the slopes. This increase is believed to have been triggered by the biological evolution of the carbonate lrapping and binding communities. Information about the biotic composition and microfa-
cies of Ladinian'reefs' is rather poor even in otherparts of the Alpine- Mediterranean region as compared with that related to late Triassic reefs (FLOomL1981, 1982). The data available for comparison of facies and biotic distributional patterns come from Ladinian (and Cordevolian) 'reef limestones' of the Southern and Northern Calcareous Alps ( B ~ r , r ~ & REscri 1981,Busm~etal. 1 9 7 2 , ~ c r i 1 9 8 2 , 1 9 8 3 , ~ C l t & Zar,rm. 1986, Ki~us & Oar 1968,Orr 1967,Pv-mvv~K1988, TtmNSEKet al. 1984, WOLFF1973, ZORN1972), Carpathians (LoBri'zm~ et al. 1990, cum lit.), Dinarides (PAmac -PRoDANOVlC 1975), Southern Apennines (CIAe,APlCAet al. 1990) and Western Anatolia (Oar 1972). Difficulties arise in the paleontological discrimination and systematic assignment of some of the important carbonate-producing organisms ('algal crusts'/Spongiostromata, porostromate algae, 'Tubiphytes", various microproblematica). A thorough classification of these fossils, however, is necessary, in order to estimate their role in the formation of platform margin and slope carbonates. In this paper we try to improve the paleontological basis and to use paleontological and microfacies data in interpreting the source area and possible origin of carbonate megabreccias exhibited in one of the most spectacular outcrops of the Dolomites. However, the results should not be overrated because of the still preliminary character of the investigations. 2 LOCATION AND GEOLOGICAL SETTING The Mahlknecht Cliff is located in the southwestern part of the Seiser Alm/Alpi di Siusi adjacent to the Schlern area east of Bozen, South Tyrol (Fig. 1). Together with the Rol3zahne/Denti di Terrarossa it forms the margin of the Schlern-Rosengarten carbonate platform. The locality can
281
Fig. 2. Middle - Upper Triassic stratigraphyoftheSchlem-Seiser Aim region. Biostratigraphy based on ammonite and conodont dating (BRANDNER &
MOSTLER 1982, KRYSTYN& GRtm~ 1974, Umactm1977 and KRYSTVN oral comm.). 1-4 mark megabreccia horizons. The position of the studied megablock is indicated by a black bar.
be reached by car via the street Castelrotto/Kastelruth Seiser Aim and the trail to the Mahlknecht/Molignon-Hfitte. The stratigraphic situation is shown in Fig. 2. The outcrop (P1. 69/1) gives an excellent overview of the depositional patterns of a paleoslope discontinuouslyfed with megabreccias, resedimented conglomerates and turbidite calcarenites. A basal megabreccia unit (number 1, Fig. 2), representing the interfingering of the base-of-slope and the basinal sediments (Wengen Formation), overlies pillow breccia and hyaloclastites. The age of the megabreccias (Marmolada Conglomerate) is Middle Langobardian. Three localities have been studied in detail: - - T h e 'yellowish' megablock of locality A (P1.69/1; Fig. 2) occurs on the topofthis megabrecciaunit 1 (BaArON~ 1982). The block exhibits a thickness of approximately 25 m. It consists of reworked volcanoclastic and carbonate material at thebase (PI. 69/2), overlain by limestone breccia exhibiting predominantly boundstone textures. The block was sampled in a vertical section. Samples GF 1 - GF 38. - - Isolated limestone boulders, differing in lithofacies, were sampled in locality B (P1.69/1) in order to define the microfacies criteria. These boulders might have been eroded from the basal unit 1or from the middle unit 2 which is characterized by large limestone blocks embedded within volcanic debris. Samples 1-9 and 10-39. - - Locality C refers to a large limestone block (thickness 5.70 m) lying on the meadow below the Mahlknecht Cliff about 200 m west of the Molignon-Haus (Mahlknechtschwaige). The block was most probably eroded from megabreccia unit 2. Samples KB 161 - KB 170.
In total, about 100 samples were used in characterizing the microfacies variation and describing the biota. The Mahlknecht Cliff samples represent allochthonous limestones formed after and during a time of strong volcanic activity. In contrast, the Ladinian megabreccias investigated byFols (1982) and Fois & GAETAr,a(I 980) were notinfluenced by coeval volcanism. Sphinctozoan sponges, algal crust types, foraminifera and some microproblematica point to a Ladirdan age of the samples. The importance of this outcrop has been recognized already by MoJslSOVICS(1879, p. 172): 'Die BedeutungderRiffsteinewirddurch dieprachtvollen Aufschliisse am stid6stlichen Abhange der Rossz~ne in lehrreichster Weise demonslriert. Bis fiber das Niveau der Mahlknechthiitte heraufreichen die Augitporphyrlaven. 0ber ihnen steigen dunkleTuffsandsteineundConglomeraterasch zu der langegezogenen, vielgezackten Mauer derRossz/thne an. Die Schichtung der Gesteine ist auBerordentlich klar. Das Fallen ist gegen Norden gerichtet. Linsenf6rmige und blockf6rmige Massen von grauem und braunem Riffstein sind zwischen den Tuffschichten regelm,'tBig eingebettet und ihrer contrastierenden Farbe wegen weithin sichtbar. Man bemerkt deutlich, wie die Tuffschichten an den unregelm~tBig geformten Riffsteinen an- und absteigen. Der Rfffstein ist hier meistens sehr dicht und arm an Fossilresten.' 3 METHODS Thin-sections of the samples were studied with regard to the taxonomic assignment and the carbonate-producing
282
potential of the organisms. The reef guild concept (FAGERSTROM1987) is used to characterize the importance of baffling, binding and constructing in a biogenic accretion. Facies types correspond to biofacies types and were differentiated according to depositional texture and common fossils. Boundstones were subdivided according to various amounts of baffling or binding/encrusting organisms and the sediment occurring together and between the sessile organisms. Facies types and biotic composition were contrasted with the distributional pattern summarized in the conceptual model of Ladinian buildups (GAETANI1981). 4
B I O T A A N D F A C I E S T Y P E S (Pls. 70-74)
Inventory
Fossils occur in all samples. The biota consist of foraminifera (P1.74), sponges (PI. 73), corals, brachiopods, bivalves, gastropods, echinoderms, ostracods and algae (solenoporaceans, porostromate algae, ? codiaceans; P1.71). In addition many microproblematica (PI. 72) occur including various types of'Tubiphytes' and biogenic 'crusts' as well as Ladinella ordinata Oar, Bacinella elongata FoIs, cf. Macrotubus babaiFols & G~'r~,a and various 'tube-like' fossils. Mostcommon are'Tubiphytes'andbiogenic'crusts' (each occurring in > 40 % of the samples), followedby calcisponges, foraminifera and echinoderms. Sponges are represented only by sphinctozoans; inozoans are completely lacking. Solenoporacean red algae, corals, gastropods and agglurinated tubes of unknown affinities occur in about 10 % of all samples. Brachiopods and ostracods are rare (< 10 %) as are
Plate Fig. 1.
Fig. 2.
69
the porostromate algae and serpulids. Table I summarizes the taxa recognized in the samples. Facies types
The limestone facies types comprise (1) boundstones, followed by (2) floatstones/rudstones, (3) wackestones and (4) packstones/grainstones. (5) In addition, a fine- and medium-grained microbreccia consisting of limestone clasts and volcanic material occurs. (1) Boundstones include bafflestones and bindstones. The following subtypes have been recognized (Pls. 70-71): - sponge bafflestone - Cladogirvanella bafflestone - Tubiphytes bafflestone/framestone(PI. 70/2) - scleractinian coral bafflestone - solenoporaceanbafflestone - micrite crust bindstone - micrite/sparite crust bindstone - festoonedcrust bindstone - festooned crustlTubiphytes bindstone Most bafflestones are characterized by a packstone to grainstone matrix consisting of densely packed grains. Them grains are peloids, micritic intraclasts, aggregate grains, coated bioclasts, fragments of'Tubiphytes' gracilis as well as foraminifera. The same grain types occur within alternating grainstone/packstonelayers (facies type4). Some bafflestones have a wackestone matrix (sample GB 35). Bindstones are formed by biogenic crusts of different composition (PI. 71/1-4):
Ladinian slope deposits; Mahlknecht Cliff, Dolomites: Boulders and megablocks Northern end of the Mahlknecht Cliff. The outcrop exhibits the Middle Triassic (Ladinian) slope deposits consisting of several carbonate megabreccia horizons alternating with volcaniclastic horizons. The megablock studied in a vertical section (locality A, samples GF 1 - GF 19; arrow) overlays a sequence of polymict microbreccias, variously-sized limestone boulders and intercalated tufts (samples GF 20 - GF 38); Fig. 2). The height of the block is 25 m. The composition of the block is summarized in Fig. 3. Locality B (samples 5-39) is the scree at the left fed by material from the lower and middle sequence. Base of the megablock. Limestone blocks are intermixed with volcaniclastic material. The limestone bed (A; wackestone with micrite crusts) is overlain by a rubble zone (B) consisting of angular and subrounded limestone boulders with different microfacies (Cladogirvanella bafflestone, bioclastic floatstone with brachiopods, boundstone with sponges), followed by a thick limestone bed (C, graded lithoclastic grainstone). The erosional top of C is overlain by the shaly horizon D with volcaniclastics (poorly sorted packstone with carbonate lithoclasts exhibiting different microfacies). Unit E is a clast-supported sandy microbreccia. F and G correspond to carbonate blocks (lithoclastic rudstone consisting of volcanic extraclasts and various limestone clasts) or breccias (poorly sorted l ithoclastic rudstone with large oncoids, volcaniclastic extraclasts and different carbonate l ithoclasts). These block layers are continued in the overlying units H (bafflestone with Cladogirvanella, bioclastic floatstone with sponges) and I (fine- and coarse-grained peloidal grainstone with volcaniclastic detritus and boundstone fabrics). Unit E 1 is an inhomogenous limestone block; unit E2 is a very typical bafflestone with a framework of solenoporacean algae and Cladogirvanella. The matrix is a brown lime mudstone with ostracods, fine shell debris, some reworked Tubiphytes and Plexoramea and Baccanella (probably of microbial origin). The arrow points to large volcanic boulders. This lower part of the section contains more limestone boulders eroded from low-energy environments than the upper part which is characterized by the dominance of low- to high-energy boundstones.
Plate
69
283
284
Foraminifera Agglutisolenia conica S~OWBARI-DARY~? * Ammobaculites/Reophax sp. Bullopora ? sp. Diplotremina ? sp. Endothyr a sp. Endothyra of. bedouxi Zah'n~'rn & BRtrC~rn~tar~ Endothyranella wirtzi KR.tSTAN-TOLLM.~CN Frondicularia sp. * Kaeveria fluegeli Z ~ a r ~
Sponges Celyphia zoldana Oar, PISA & FARAB~C,OU * Colospongia catenulata catenulata Oar Deningeria sp. * Diecithalamia polysiphonata Dmc~, AacroN^c~ & ZARDt~a FoUicatena caulica Oar Solenolmia manon manon (MONSTER) UvaneUa irregularis oar Vesicocaulis alpinus Or'r
Vesicocaulis depressus Oar *
Corals Mar gar osmilia septanectens (LoReTZ) Margarophyllia crenata (MONSTER)* Proheterastraea sp. Toechastraea sp.
Algae Parachaetetes sp. Solenopora sp. Bevocastria ? sp. (or Macrotubus babai FoIs) Cladogirvanella sp. Ortonella sp. Ortonella cf. myrae RAcz
Microproblematica Biogenic crusts, various types Baccanella floriformis Pam:tc Bacinella elongata FoIs LadinelIa porata Orr * Plexoramea cerebriformis MELLO 'Tubiphytes' sp., various types 'Tubiphytes' gracilis SCrOa~ER& S,~'~OWB~-DARYAN
Table 1. Biotic inventory of the Ladinian megablock and other boulders (*) of the Mahlknecht cliff. Micrite crusts (PI. 71/3) are characterized by widely spaced irregular thin, micrite laminae separating packstone areas composed of densely packed micrite grains. Within these areas very fine, horizontally and vertically arranged f'damentsoccur (diameter about 15 I.tm).These crusts alternate with micrite layers and very fine-grained grainstones exhibiting dome-shaped structures (GB 9) occurring together with the baffling microproblematicum BacineUa elongata Fols (PI. 71/9-11). Sample GB 8 shows the association of the micrite crusts with sphinctozoan sponges, Baccanella and fibrous cement fans. Micrite/sparite crust bindstones (PI. 70/4) are characterized by irregularly shaped, discontinuous micrite laminae alternating with sparite and microsparite layers. The thickness and spacing of these layers vary strongly. Some micritic laminae contain very small laterally arranged filaments. These crusts occur within a fine-grained packstone/grainstone malrix containing large spar-filled voids. Some of the crusts form nodules, others are laterally spread. Festooned crust bindstones (P1.71/4) are characterized by festoon-shaped crusts consisting of thin micrite laminae and thicker sparite areas (P1.70/1). The sparite layers consist
Plate Fig. 1. Fig. 2
Fig. 3.
Fig. 4.
70
of long fibrous calcite crystals forming fan druses. The syndepositional character of these cements isevidentbecause of multiple cement generations encrusted by micrite laminae and the incrustations of the crystals by foraminifera. This is the most common crust type. Festooned crustlTubiphytes crusts are characterized by the occurrence of Tubiphytes, sponges and a large amount of synsedimentary fibrous cement. Other important criteria of the boundstones are mm- to cm-sized spar-filled voids corresponding to constructional cavities (PI. 71//2). Isolated samples collected below the Mahlknecht Cliff exhibit voids partly or totally filled with volcanic debris. (2) Floatstones are representedby lithoclastic floatstones/ rudstones (PI. 70/3) and by oncolitic floatstones. The oncoids vary in size between 0.5 and 1.5 cm. The densely spaced micritic layers are crinkled. Very small spar-filled filaments occur within these layers. The layers are encrusted by foraminifera and spar-filled tubes with agglutinated walls as well as by Tubiphytes. The nuclei are gastropods, echinoderms and also solenoporecean algae. The matrix is micrite and
Facies types of Ladinian slope boulders: Mahlknecht Cliff scree, Dolomites Crust boundstone characterized by festooned biogenic crusts (black, bottom left) occurring together with sponges. This is the most common crust type. Sample 23. x 4 Tubiphytes boundstone. Note the peloidal matrix. Tubiphytes, encrusted by foraminifera, forms an organic framework but acted also as baffler. Constructional cavities are filled with sediment and blocky calcite. Sample 22. x 4.5 Polymict microbreccia consisting of poorly sorted carbonate clasts and volcanic clasts (bottom right). Note the difference in size, angularity and microfacies Most clasts are peloidal packstones, some are boundstones with Tubiphytes (top right). Fossils are represented by crinoids, gastropods and foraminifera. Sample 12. x 4 Compound boundstone. Bioclasts (e.g., center: coral) are encrusted by sponges and micrite/sparite crusts. These biogenic encrustations were responsible for the formation of round boulders. Sample 25. x 4
Plate
70
285
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poorly sorted biointraclastic packstone/grainstone. Oncolitic floatstones are conspicuous within an interval of about 1 m in the section of locality A but also occur in locality B (samples 23, 25, 36, 37). The oncoids are regarded as being derived from the platform.
and of the Carnic Alps (P~'FZR 1988). The platform margin or slope sands are distinctly different from carbonate sands derived from the platform. These sands are characterized by a mixture of aggregate grains, green algae, foraminifera and a few ooids.
(3) Wackestones are rare. Sample GB 19 is a bioclastic wackestone with Tubiphytes, bivalve shells and fibrous cement occurring in patches. Sample GB 33 is a bioclastic wackestone mit pelecypod shells, brachiopods, sponge spicula and ostracods. Sample GB 36 exhibits a wackestone texture alternating with a bindstone texture.
(5) Microbreccias (PI. 70/3) are characterized by poor sorting, a medium- to coarse-grained rudstone fabric and a mixture of carbonate lithoclasts, islolated fossils and volcanic lithoclasts. This type is restricted to the lower part of the block sampled in locality A (P1.69/2). The subrounded and angular carbonate lithoclasts are grainstones, packstones and bindstones as well as wackestones with thin shells. Fossils areTubiphytes fragments, various 'tubes', sponges, echinoderms, shells and solenoporacean thalli. The grains are cemented by blocky calcite. Sample GB 31 is a sandy tuffite with only a few carbonate clasts.
(4) Limestones exhibiting only packstone and grain stone textures without encrusting or baffling organisms axe rare. Grains are represented by micritic peioids (< 30 larn) surrounded by thin fringes of isopachous cement; micrite intraclasts and a few foraminifera. Characteristically wavy layers alternate, composed of differently sized grains (samples GB 7, 27, 29). Some samples show a repeated sequence of t-me-grained and coarse-grained grainestone fabrics (GB 21), others a mixture of carbonate and volcanic lithoclasts and fossils). These microfacies types correspond roughly to microfacies types described from other Ladinian 'platform margin' carbonates of the Dolomites (GAETANIet al. 1981)
Plate
Fig. 1.-4.
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4 SEDIMENTOLOGICAL ROLE OF THE ORGANISMS Boundstone types distinctly dominate within the total samples (Fig. 3). Bafflestones and bindstones are equally differentiated according to the organisms involved in the formation of these fabrics but bindstones generally occupy a larger volume than bafflestones. The percentage of bind-
Ladinian slope boulders, Mahlknecht Cliff. Binding and baffling organisms: Biogenic crusts, solenoporacean .algae and porostromate, microproblematica
Biogenic crusts, probably formed by microbial/algal activity and submarine cementation, were the most common elements contributing to the formation of bindstones. Fig. 1. Micrite/sparite crusts (lower left) and festooned crusts, associated with Tubiphytes (center) and sponges (left). Sample GF 23. Megablock, base of unit I. x 9.5 Fig. 2. Oncolithic micrite crusts overgrowing strongly disturbed (bored ?) micrite/sparite crusts. The white spots within the micrite crust are spar-filled filaments (and borings ?). Oncolithic floatstone. Sample 15c. Megablock. x 5 Fig. 3. Peloidal micrite crust characterized by alternating zones with densely packed micrite peloids and micrite bands. These crusts are associated with a packstone and grainstone matrix. Sample GF 11. Megablock. x 6.5 Fig. 4. Festooned crust bindestone characterized by festoon-shaped, laterally extended crusts consisting of irregular, interrupted micrite laminae and cement-filled interspaces. Small t-daments occur within the micrite laminae. This is the most common crust type. Sample 6. Megablock, locality A. x 12 Figs. 5.-7. Solenoporacean red algae These algae contributed to the sedimentation by baffling (Fig. 5), to a minor degree also by forming smallscaled frameworks (Fig. 6). Figs. 5 and 6 show Parachaetetes sp., Fig. 7 Solenopora ?, characterized by sparfilled cavities incorporated within the net-like thallus. Fig. 5: Sample GF 35, megablock locality A. x 2.5; Fig. 6: Sample 31, isolated boulder, locality B. x 2.5; Fig. 7: Sample GF 12, locality A. x 9.5 Figs. 9.- 11. Bacinella elongata Fols, a common baffling organism occurring in close association with micrite crusts. The fossil is interpreted, with some doubt, as an alga. Fig. 9: Sample GF 12, megablock locality A. x 25; Fig. 10: Sample 57. Autochthonous mound rock, Goldknopf area. x 20; Fig. 11: Sample GF 12, locality A. x 12 Figs. 12.-14. Porostromate algae are of minor importance in baffling. Fig. 12: Ortonella cf. myrae RACZ.Sample GF 13a, x 12; Fig. 13: Ortonella sp. contributing to the formation ofcm-sized biogenic crusts. Sample GF 15a, x 15; Fig. 14" Bevocastria ? sp. The taxonomic assignment of this common form is uncertain. The constricted, bifurcated tubes exhibit similarities with the microproblematicum Macrotubus babai Fore, a common baffler in the Ladinian Civetta buildup. Sample GF 5, megablock locality A, x 12
Plate
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larger fossils and skeletal grains, with a minor contribution o f foraminifera, echinoderms and 40% ostracods. The rest is formed by intraclasts and lithoclasts as well as by very small peloids. These peloids may be of microbial origin 30~ because of the striking similarities with peloidal precipitates, possibly resulting from bacterial activity. Similarities include: 20% (a) occurrenceofpeloids as infilling sediment between bafflers oras matrix sediment forming the bulk of some bindstones (e.g., micrite 10% Ru~ton~ crust bindstones); (b) many peloids are sur2 ~ rounded by rims of radially oriented bladed calcite crystals; (c) occurrence in layers defined by a change in the size of peloids; Fig. 3. Megabrecciaboulders: Frequencyof depositional texturetypesbased on (d) peloidal packstone is generally poor in a hundredsamples from the megablockand from loose samples collected in the microfossils. A microbial origin of similar scree. Boundstonesare bindstones and bafflestones.Framestonesare very rare. peloids has been infered from the comparison with recent precipitated Mg calcite peloids stone fabrics per sample varies between 30 % and 100 % (CaAvETZ 1986, REID 1987, Busz'vNsra & CtU~VEXZ1991). High-growing communities are rare and represented (festooned crust bindstone) but is commonly > 50 % of the rock volume. only by corals. Some of the crusts (micrite crusts, micrite/sparite crusts) Most sponges, 'Tubiphytes' gracilis, Cladogirvanella are similar to cement crusts of the Wetterstein limestone of sp., solenoporacean algae and some microproblematica (e.g., the Northern Alps, which are believed to have been induced Bacinella elongata) are members of low-growing by a control of microenvironments by the metabolism of communities which contribute to the trapping (and to a spongiostromate algae (HErqRICH& Zhrcg~ 1986). lesser degree baffling) of sediment between the only several The most frequent bindstone type characterized by the cm-sized organisms. About 40 % of the sediment is of festooned crusts, however, obviously has no recent counterbioclastic origin, e.g., resulting from the degradation of Bindstone
Percenlage of facies types
~aor
Plate
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Fig. 1.-5.
Ladinian slope boulders, Mahlknecht Cliff: Organisms of doubtful systematic assignment (microproblematica) contributed much in the formation of boundstones as well as in bioclastic grainstones
Tubes characterized by stacked segments These forms can by taxonomically differentiated according to the wall structure. Fig.. 1: Form A. Sample GF 36a, megablock locality A. x 5. Figs. 2-4: Form B. Fig. 2: Sample 3, isolated boulder, scree above the Mahlknecht. x 23. Fig. 3: Sample 17, scree Mahlknecht. x 7.5. Fig. 4: Autochthonous mound rock, Goldknopf area. Sample 118. x 10. Fig. 5: Form C ? Sample GF 10, megablock locality A. x 16 Fig. 6.-10., 15. 'Tubiphytes". Fossils commonly attributed to the enigmatic genus Tubiphytes MASLOVcomprise organisms of different systematic position and different sedimentological significance. Fig. 6: Tubiphytes sp. frequently occurring together withbubble-like, thin-shelled fossils. Sample 16, scree Mahlknecht. x 30. Fig. 7: Tubiphytessp. Note the spar-filled tubes restricted to individualized segments. Sample 16, scree Mahlknecht. x 9.5. Fig. 8: 'Tubiphytes' characterized by thin encrusting growth forms. Sample GF 4, megablock locality A. x 30. Figs. 9-10: Plexoramea cerebriformis ME~O,exhibiting affinities with marine fungi (cf. FL~3G~et al. 1988). Sample GF 21. Megablock, locality A. Both Figs.: x 20. Fig. 14: 'Tubiphytes'gracilis SCaAr'ER& SENOWBARI-DAaY~. Reworked branches of this species contribute to more than 60 % of the skeletal grains of grainstone/packstone sediment occurring between baffling and binding organisms. Sample GF 13b. Locality A, megablock, x 34 Fig. 11. Ladinella porata Orr, an encrusting microproblematicum. Sample 37, scree Mahlknecht. x 42 Fig. 12. Clad•girvanellasp.Thecm-sizedstrubs•fthesea•gae(?)wereimp•rtantbaff•ers.Samp•eGF34•megab•ock locality A. x 5 Fig. 13. Problematicum 1 SENOWBAPa-DARY~1981. Sample GF 9. Megablock, locality A. x 9.5 Fig. 14. Large and small tubes (worm tubes ?) with dark microcrystalline calcite walls (Fig. 14 and PI. 74/18) as well as well-differentiated calcite walls (PI. 74/17) are common biotic elements of the boundstone and floatstone facies. Sample GF 11. Megablock. x 2.5
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290 part. Very small filaments occcurring within the micritic laminae may be relicts of cyanobacteria which were rapidly destroyed, as indicated by the interrupted micrite layers of the micrite/sparite crust type. BRACrmRT& Dtax~ (in press) stress the morphological and compositional similarities between laminar micrite crusts occurring at a depth below 120 m on ledges on steep foreslopes of recent Red Sea reefs and of 'spongiostromate crusts' from the 'middle slope' of the Ladinian Civetta reef (Fols & GAETANI1980) and of Cipit blocks. These spongiostromate crusts comprise some of the crust types differentiated above (micrite crusts, micrite/sparite crusts). Similarities include the composition of the Triassic crusts with irregular, wavy and dome-shaped laminae, a change of more dense and more open layers, an abundance of encrusting organisms, the occurrence of botryoidal cement and the association with reef blocks. The Holocene micrite crusts are interpreted as the result of microbial activity and cementation at the boundary seawater/hard substrate during sea-level rise. A lithification at the surface of the submarine foreslopes is also assumed for the Triassic (BosELLn,a & DOCLIONI1988). Mostofthe boundstone samples contain various amounts of early diagenetic submarine cements (up to 60 %). The most common type is a radial-fibrous (and botryoidal)
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cement occurring within constructional cavities andbetween micritic laminae of biogenic crusts. Isopachous-fibrous cement occur, sometimes with several generations, within interparticle pores as well as in enlarged constructional cavities. These cement types are the same as in Cipit blocks described by BmOLE(1981). The high amount of submarine cement within bindstones is a well known criteria of Middle Triassic (and Permian) 'reel" limestones (FLOG'EL1989, LoBrITr.Ret al. 1990). It is commonly explained by the leeward position of the reefs facilitating the constant movement of vast quantities of supersaturated marine waters through an organic framework (MooRE 1989). This would presuppose that the associations forming the festooned crust bindstones were still located within a high-energy shallow-marine environment.
5 CONCLUSION (1) The megablock investigated is composed of carbonate boulders of various size (a few centimeters up to > 1 m) and shape (angular, subrounded, well-rounded) exhibiting different microfacies types (predominantly boundstones and bioclastic floatstones). Rotated geopetal fabrics within the boulders argue against the explanation as in situ'patch reefs'
Ladinian slope boulders, Mahlknecht Cliff: Sphinctozoan sponges
The sponge fauna is relatively diverse but the taxa are represented by only a few specimens. The most frequent species is Solenolmia manon manon followed by Vesicocaulis alpin~. Most sponges acted as bafflers except for the encrusting Uvanella irregularis. Fig. 1.-4.
Fig.
Fig.
Fig. Fig. Fig. Fig. Fig. Fig.
Vesicocaulis alpinus Oar is known from Upper Ladinian, Cordevolian and Julian reef carbonates of the Northern Alps and Western Carpathians. Fig. 1: Longitudinal section exhibiting the spongocoel (lower part) and the characteristic sieve-plates of the outer wall (lowermost chamber). Sample GF 13. Locality A, megablock, x 5. Fig. 2: Longitudinal section. Same sample, x 2.5. Fig. 3: Detail of Fig. 2 exhibiting the filling structure around the spongocoel, x 6.5. Fig. 4: Oblique section. Note the filling structures. Same sample, x 16 5.-6. Solenolmia manon manon (Mt3NS~R),a common sponge in Anisian to Carnian reef carbonates of the AlpineMediterranean region. Fig. 5: Longitudinal section exhibiting the spongocoel (center). The sponge is overgrown by micrite/sparite crusts. Sample GF 18. Locality A. x 5. Fig. 6: Longitudinal section. Sample 12. Scree, Mahlknecht Cliff.. x 6.5 7., 10.-11. Follicatena cautica Or'r, a common sponge in Ladinian and Carnian reef carbonates of the AlpineMediterranean region and of the Pamir range. Fig. 7: Sample GF 38. Locality A, lower part of the megablock, unit B. x 4. Fig. 10: Intergrowth of micrite/ sparite crusts and calcisponges. Sample lb. Locality B, scree Mahlknecht. x 6. Fig. 11: Sample GF 25. Megablock. x 5 8.-9. Deningeria sp. Sample 21. Scree, Mahlknecht. Fig. 8. Note the fine reticular filling structures within the chambers, x 5. Fig. 9. Same sample, x 7.5 12.- 13. Uvanella irregularis Orr, a common encrusting sponge Ladinian and Carnian reef carbonates. Fig. 12. Sample GF 8. Megablock, locality A. x 8. Fig. 13. Same sample, x 9 14. Colospongia catenulata catenulata Oar. Longitudinal section. Sample GF 8. Megablock. x 12 15. Diecithalamia polysiphonata (DrEC~, Arcror~ACO & ~ n , ~ ) . Marginal section exhibiting the glomerate arrangement of the chambers. Sample GF 8. Locality A, megablock, x 9.5 16. Vesicocaulis depressus Orr. Sample 39. Locality B, scree Rif. Molignon. x 13 17.-18. Celyphia zoldana Or'r, lhsA & FARAaEC_,Ota.Sample 21. Scree, Mahlknecht. Fig. 17: x 9.5. Fig. 18: x 16
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and demonstrate impressively the redeposition of lithified carbonates. (2) 'Rounded' boulders are caused by organic envelopes and not by transport. (3) Facies types and biotic composition of the boulders of the Mahiknecht cliff fit surprisingly well with the 'high elevation buildup model' developed by GAE'rAr~et al. (1981). This model is based on the distribution patterns recognized on the paleoslopes of the Sass da Putia buildup and of the Civetta buildup. Our facies types correspond to those described from the upper slope (solenoporacean bafflestone, sphinctozoan/ Tubiphytes bafflestone, colonial scleractinian bafflestone) and the middle slope ("olue-green algal boundstone' corresponding to the rnicrite/sparite bindstone and the festooned crust bindstone). This correspondence point to - - a formation of bioconstructions by low-growing organisms and submarine cementation at the upper foreslope, - - reworking within different parts of the slope, resulting in the formation and the transport of microfacially differentiated carbonate boulders, - - gravity-induced downslope transport possibly alternating with phases without transport as indicated by boulders with abundant micfite crusts and by an infilling of calcarenitic sediments derived from the 'matrix' between the boulders of the megablock. (4) Comparable to the Civetta and Sass di Putia examples
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only very rare platform- or platform-margin derived material (e.g., ooids) was detected in our samples, indicating that the facies types of the megabrer,.ciaseem to have been eroded not from a platform-margin but from various parts of the upper slope. The dominance ofmicritic sediment and of lowgrowing organisms as well as the absence of indications of meteoric-vadose diagenesis within the megablock point to a subtidal position of the source area and to submarine erosion of bioconstructions formed within the source area by binding and baffling organisms. (5) Microbes or microbially induced calcium carbonate crusts were of major importance in the organic stabilization of the upper slope. A characteristic sequence would include: Growth of microbial films on the slope- trapping of sand grains- formation ofbiogenic crusts (bindstones)- irregular growth of the crusts (festoonedcrusts) forming larger biogenic structures - reworking of these structures and deposition on the slope- encrustation of the redeposited clasts resulting in the formation of 'rounded' boulders. (6) The megablock study would indicate that the slope was fed with autochthonous biogenic carbonates produced on the slope rather than with platform -margin reef carbonates as assumed by the classical models (MoJsISOVICS1879). This situation, in comparison with the Latemar buildup (GOLOr~MrVmR& HARRIS1989) WOuldindicate a sea-level highstand, during which both the platform and the platform margin/ upper slope were submerged. Boundstones formed the bulk of the foreslope clasts, whereas redeposited shallow-water sands were deposited at the toe-of-slope and in the basin.
Ladinian slope boulders, Mahlknecht Cliff, Dolomites: Foraminifera (Figs. 1-16) and microproblematica (Figs. 17-19)
Foraminifera are represented predominantly by agglutinated species (both mobile and encrusting forms) as well as by a few polymorphid and nodosariid species Fig. 1.-4. Fig. 5. Fig. 6.-7. Fig. 8. Fig. 9. Fig. 10.-11. Fig. 12.-13. Fig. 14.-15. Fig. 16. Fig. 17.-19.
Reophax/Ammobaculites sp.. Fig. 1. Sample GF16A, megablock, x 21. Fig. 2. Sample GF 16. Oncolithic floatstone, x 27. Fig. 3. Sample GF 14. x 27. Fig. 4. Sample GF 16A. x 50 Dustominidae (Diplotremina ? sp.). Sample GF 15b. Oncolithic floatstone. Megablock. x 70 Endothyranella wirtzi KPaSTAN-ToLLMA~.Fig. 6. Sample 1 lc. Coral bafflestone. Scree Mahlknecht cliff. x 65. Fig. 7.: Sample GF 11 Bioclastic grainstone Megablock, unit B. x 55 Frondicularia sp. Sample 37. Scree, Mahlknecht cliff. Oncolithic floaststone, x 70 Encrusting foraminifera similar to Bullopora sp. Sample GF 12. Boundstone. Megablock. x 30 Encrusting agglutinated foraminifera. Fig. 10. Sample GF 1. Boundstones with'Tubiphytes'and solenoporacean algae. Fig. 11. Sample GF 3. Megablock. Magnification for both figures is x 70 Agglutisolenia conica SE~OWaARI-DARVAN? Sample 16. Scree Mahlknecht cliff. Magnification for both figures x 70 Endothyra cf. E. badouxi ZAr,~rn & B R O ~ . Fig. 14. Sample GF 34. Megablock, unit B. x 70. Fig. 15. Locality as in Fig. 14. x 70 Kaeveriafluegeli ~ et al. Peloidal grainstone. Sample GF 7. Megablock, locality A. x 70 Microproblematica, perhaps worm tubes. Fig. 17. Sample 5. Boundstone. Scree Mahlknecht cliff, x 14. Fig. 18. Sample 19, scree Mahlknecht cliff, x 16. Fig. 19. Sample 21. Boundstone. Scree, Mahlknecht cliff, x 20
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ACKNOWLEDGMENTS The paper was prepared in connection with the'Dolomieu Conference on Carbonate Platforms and Dolomitization, 1991", Ortisei/St.Ulrich, in memory o f Deodat de Dolomieu and his discovery of dolomite two hundred years ago. Substantial help in the field was given by Lyndon Yose (The Johns Hopkin's University, Baltimore) and Roman Koch (Erlangen) who took the samples from the megablock section of locality A. The study is part o f current investigations of Ladinian reefs in the Alps supported by the Deutsche Forschungsgemeinschaft.
REFERENCES BmOLE,K.T. (1979): Characteristics of Triassic carbonate buildups, Dolomite Alps, Italy: evidence from the margin-to-basin depositional system. - Diss. Rice Univ., 216 p., Houston -- ( 1981): The basal Cipit boulders: Indicators o fMiddle to Upper Triassic buildup margins, Dolomite Alps, Italy. - Riv. Ital. Palaeont. Strat., 86, 779-794, Milano -- (1984): Triassic sea-level change and the Ladiman-Carnian stage boundary. - Nature, 308, No. 5960, 631-633, 2 Figs., London B trCZYNSlCJ,C. & CHA~TZ,H.S. (1991): Habit of bacterially induced precipitates of calcium carbonate and the influence of medium viscosity on mineralogy. - - J. Sed. Petrol., 61/2, 226-233, 3 Figs., Tulsa Bt.~rD~C~R,W. & BL~DINGm,E. (1989): Windward-leeward effect on Triassic carbonate bank margin facies of the Dolomites, northern Italy. - Sed. Geol., 64, 143-166, 18 Figs., Amsterdam Bosr~ts~, A. (1984): Progradation geometxies of carbonate platforms; examples from the Triassic of the Dolomites, northern Italy. - Sediment., 31, 1-24, 20 Figs., Oxfo/d -- (1989): Dynamics of Tethyan carbonate platforms. - Soc. Econ. Paleont. Min. Spec. Publ., 44, 3-13, 13 Figs., Tulsa Bos~,~a, A. & Dootao~a, C. (1988): ~ field trip in the Dolomites. Guidebook. - Amer. Ass. Petrol. Geol. Meeting, Nizza 1988, 42 p., Tulsa Bos~J.l.~, A. & Rossr, D. ( 1974): Triassic carbonate buildups of the Dolomites, Northern Italy. - S o c . Econ. Paleont` Min. Spec. Publ., 18, 209-233, 33 Figs., Tulsa BRACrW_~T,T. & Dta~o, W.Cm~. (in press): Laminar micrite crusts from Red Sea forereefs. - L Sed. Petrol., Tulsa BR~R, R. (1982): Mittel- und Obertrias in Frrtschbach und Seiser Aim. - Exkursionsftthrer Jahrestagung Osterr. Geol. Ges., Seis aan Schlern, Sildtiro11982, 80-97, 6 Pls., Innsbruck BR~'Cor,'m,R. & MosTu0~ H. (1982): Der geologische Aufbau des Schlerngebietes und seiner weiteren Umgebung. Exkursionsftthrer. Jahrestagung Osterr. Geol. Ges., Seis am Schlern, Sfidtirol 1982, 1-42, 3 Pls., 19 Figs., Innsbruck BL~'CD~R,R. & RBSC~,W. (1981): Reefdev elopment in the Middle Triassic (Ladinian and Cordevolian) o f the Northern Limestone Alps near Irmsbruck, Austria. -Soc.. Econ. Paleont. Min. Spec. Publ., 30, 203-23 I, Tulsa Bus~, ST., RJ~iovs, A. & T~SEK, D. (1982): Triassic Reefs in Slovenia. - Facies, 6, 15-24, 2 Figs., Erlangen CHAWTZ, H.S. (1986): Marine peloids: a product of bacterially induced precipitation of calcite. - J. Sed. Petrol., 56, 812-817, Tulsa ~Ica, G., Cn~n.IJ, S., M ART~ R., RE'ITORI,P., S ALVmIB ONARD, G. & ZAmNE'rrI,L. (1990): Carbonate buildups and associated facies in the Monte Facito Formation (Southern Apennines).Boll. Soc. Geol. Ital., 109, 151-164, 11 Figs., Roma CROS, P. (1967): Origine des certains blocs calcaires de 'Cipit' du
Trias Dolomitique. - C. R. Acad. Sci., 556-559, Paris -- (1974a): I~volution s&timentologique et palrostructurale de quelques plate-formes carbonatres biog~nes (Trias des Dolomites italiermes). - Sci. Terre, 19, 299-379, Paris -- (1974b): Un module de srdirnentation carbonat~e marine: les platformes dites r&zifales du Trias des Dolomites et leur environnement.-Diss. Univ. Paris VI, 4 volumes, 888 p., Paris FAG~RSTROM,J.A. (1987): Tlae evolution of reef communities.- 600 p., New York (Wiley) FL0O~, E. (1981): Paleoecology and facies of Upper Triassic reefs in the Northern Calcareous/Ups. - S o c . Econ. Paleont. Min. Spec. Publ., 30, 291-359, Tulsa -- (1982): Evolution of Triassic reefs: Current concepts and problems. - Facies, 6, 197-228, Erlangen -- (1989):'Algen/Zement'-Riffe.-Arch. Lagerstattenforsch.Geol. Bundesanst., 10, 25-32, 4 Figs., Wien FLOOEt.,E., RmDEL,P. & SFa~OWBa~,I-DARY~,B. (1988): Plexoramea cerebriformis MZt.LO,ein h~iufiges Mikrofossil in triadischen Flachwasserkalken: Alge oder Pilz ? - Mitt. Ges. Geol. Bergbaustud. Osterr., 34/35, 263-277, 3 Pls., Wien Foxs, E. (1982): The Sass da Putia carbonate buildup (western Dolomites): Biofacies succession and margin development during the Ladinian. - Riv. Ital. Paleont. Strat., 87/4, 565-598, Pls. 44-45, 10 Figs., Milano FoIs, E. & GAETANI,M. (1980): The northern margin of the Civetta buildup. Evolution during the Ladinian and the Carnian. - Riv. Ital. Paleont. S trat`, 86/3,469-542, Pls. 49-56, 18 Figs., Milano Ft~RSICH,F.T. & WENDT,J. (1977): Biostratigraphy and palaeoecology of the Cassian Formation (Triassic) of the Southern Alps.-Palaeogeogr., Palaeoclimatol., Palaeoecol., 22, 257-323, 26 Figs., Amsterdam G~T~-I, M. (1979, ed.): Field Guide Book, Riccardo Assereto and Giulio Pisa Field Symposium on Triassic Stratigraphy in Southern Alps, Bergamo, 1979, 73 p., Bergamo G~TANI, M., Fore, E., JAootn~D,F. & NtCORA,A. (1981): Nature and evolution o f Middle Triassic carbonate buildups in the Dolomites (Italy). - Marine Geology, 44, 25-57, 15 Figs., Amsterdam GOLDHAMM~, R.K. (1988): Platform carbonate cycles, Middle Triassic of Northern Italy: The interplay of local tectonics and global eustady. - Unpubl. PhD Thesis, Johns Hopkins Univ., 446 p., Baltimore GOLOHAMMER,R.K. & HARRIS,M.T. (1989): Eustatic controls on the stratigraphy and geometry of the Latemar buildup (Middle Triassic), the Dolomites of Northern Italy.- Soc. Econ. Paleont. Min. Spec. Publ., 44, 323-338, 18 Figs., Tulsa HARRIS,M.T. (1988): Margin and foreslope deposits of the Latemar carbonate buildup (Middle Triassic), the Dolomites, northern Italy. - Unpubl. PhD. Thesis, Johns Hopkins Univ., 473 p., Baltimore H~,~RIC~,R. ( 1982): Middle Triassic carbonate margin development: Hochstaufen-Zwieselmassiv, Northern Calcareous Alps, Germany.- Facies, 6, 85-106, Erlangen -- 1983): Der Wettersteinkalk am NW-Rand des tirolischen Bogens in den N0rdlichen Kalkalpen: Der jthagste Vorsto8 einer Flachwasserplatfform am Begirm der Obertrias.- Geologica et Palaeontologica, 17, 137-177, 9 Pls., 7 Figs., Marburg H0a,n~cn, R. & 7_aM~, H. (1986): Diagenesis of Upper Triassic Wetterstein reefs of the Bavarian Alps. - In: SCrmOEDFa~,J. & PURSER,B.H. (eds.): Reef diagenesis, 245-268, 9 Figs., Berlin (Springer) KzN'r~, J.A.M. (1990): C arbonate platform flanks: s lope angle and sediment fabric. - Sedimentology, 37/5, Oxford KRAUS,O. & On', E. (1968): Eine ladiniscbe Rift-Fauna im Dobratsch-Gipfelkalk (KLrnten, Osterreich)undBemerkungen zum Faziesvergleich yon Nordalpen und Drauzug. - Mitt. Bayer. Staatssamml. Paltiont. hist. Geol., 8, 263-290, Pls. 17-20, 3 Figs., Mtlnchen KRYSTYN,L. & GRtraaR,B. (1974): Daonella lommeli (WISSMANN) im Hallst~tter Kalk der Nrrdlichen Kalkalpen. - N. Jb. Geol. Paltiont., Mh., 1974/5, 279-286, Stuttgart
295
I.,SONARDLP. (1961): Triassic coralligenous reefs in the Dolomites. - Ann. Univ. Ferrara, 8, 127-157, 20 Figs., Ferrara -- (1967): Le Dolomiti. Geologia dei Monti tra Isarco e Piave. 1, 552 p., 2, 1019 p., Rovereto (Manffini) -- (1979): Considdrations sddimento-stratigraphiques sur les 'recffs' triasiques des Dolomites (Italic). - Mere. Atti Accad. Naz. Lincei, C1. Sci. Fis. Mat. Nat., 15, 69-76, Roma I.~rARDI, P. & Ross%D. (1957): La scogliera coralligena del Serla nelle Dolomiti occidentali.- Ann. Univ. Ferrara, N.S., Sez. IX, Sci. Geol. Paleont., 3/1, 1-36, 9 Pls., 27 Figs., Ferrara LoBrr'maz,H., Mp~xroL,G.W., MAzztna~, S.J. & Me~o, J. (1990): Comparative study of Wetterstein carbonate platforms of the easternmost Northern Calcareous Alps and West Carpathian Mountains: Preliminary results. - In: M~ARnCOVA, D. & LoBnz~, H. (eds.): Thirty years of geological cooperation between Austria and Czechoslovvakia, 136-158, 6 Pls., 9 Figs., Wien-Praha MotstsovIcs, E.M. (1879): Die Dolomit-Riffe yon Sttdtirol und Venetien.- 551 p., Wien (H61der) MooRe, C.H. (1989): Carbonate diagenesis and porosity. - Dev. Sed., 46, 338 p., Amsterdam (Elsevier) Orr, E. (1967): Segrnentierte Kalkschwiimrne (Sphinctozoa) aus der alpinen Mitteltrias und ihre Bedeutung als Riffbildner im Wettersteinkallc -Bayer. Akad. Wiss., math.-naturwiss. KI., Abh., N.F., 131, 1-96, 10 Pls., 9 Figs., Mttnchen -- (1972): Mitteltriadische Rifle der N6rdlichen Kalkalpen und altersgleiche Bildungen auf Karaburun und Chios (,~gtiis). Mitt. Ges. Geol. Bergbanstud., 21, 251-276, 2 Pls., 7 Figs., Innsbruck PA~rnc-PRoDANOVIC,S. (1975): Les microfacies triasiques des Dinarides. - Soc. Sci. Arts Montenegro, C1. Sci. Nat., Monograph., 4, 56 p., 100 Pls., Titograd PFm~raz, J. (1988):Paleontology and microfacies of a platform margin in the Camic Alps (Austria, Middle Triassic). - Facies, 19, 33-60, Pls. 7-14, 6 Figs., Erlangen REID,R.P. ( 1987): Nonskeletalpeloidal precipitates in UpperTriassic reefs, Yukon Territory (Canada).-J. Sed. Petrol., 57, 893-900, 8 Figs., Tulsa RacrlTHOV~, F. (1860): Geognostische Beschreibung der Umgebung yon Predazzo, St. Cassianland der Selser Alpe in Sildtirol, 327 p., Gotha Rossr, D. (1957): La scogliera del Latemar (note preliminari). Ann. Univ. Ferrara, Sez. 9, 2, 213-241, Ferrara -- (1959a): La scogliera del Sasso Lungo (con alcune considerazioni sul Trias delle Dolomite occidentale). - Studi Trentini Sci. Nat., 36, 10-48, Trento -- (1959b): La scogliera del Catinaccio.- Studi Trentini Sci. Nat., 36, 10-48, Trento Russo, F., N~va, C., MASrRANDBA,A. & L^oal, G. (1991): Depositional and diagenetic history of the Alpe di Specie (Seelandalpe) fauna (Carnian, Northeastern Dolomites). Facies, 25, 187-210, Pls. 49-55, 5 Figs., 10 Tabs., Erlangen SCaaZ~R, M. (1977): Preservation, alteration and multiple cementation of aragonitic skeletons from the Cassian beds (U. Triassic, Southern /kips): Petrographic and geochemical evidence. - N . Jb. Geol. Pal~tont. Abh., 154/2, 213-262. Stuttgart Ttn~smr D., B us~, S. & OOOROLr~c,B. (1984):The role of corals in Ladinian-Camima reef communities in Slovenia, Yugoslavi&- Palaeontographica Americana, 54, 202-209, 9 Figs., Ithaca URtaCns, M. (1977): Zur Altersstellung der Pachycardientuffe und der Unteren Cassianer Schichten in den Dolomiten/halien). Mitt. Bayer. Staatssammlung Paltiont. hist. Geol., 17, 15-25, Mthachen W~'DT, J. (1980): Coral-sponge reefs in the South Alpine Upper Triassic. - In: HARTMAN,W., WENDT,J. & WIEDENMAIER,F. (eds.): Living and fossil sponges - notes for a short course. Sedimenta, 8, 122-130, Miami -- (1982): The Cassian patch-reefs (Lower Camian, Southern A1ps). - Facies, 6, 185-202, Pls. 25-26, 4 Figs., Erlangen
-- (1986): Progradation geometries of carbonate platforms: examples from the Triassic of the Dolomites, northern Italy. Sed., 33, 445-451, 4 Figs., Oxford WOLFF, H. (1973): Fazies-Gliederung und Pal~logeographie des Ladin in den baycrischen Kalkalpen zwischen Wendelstein und Kampenwand. - N. Jb. Geol. Paltiont. Abh., 143/2, 246274, 7 Figs., Stuttgart ZORN, H. (1972): Mikrofazielle Analyse eines mitteltriadischen Riftkomplexes in den Tessiner Alpen. - Mitt. Ges. Geol. Bergbaustud. Osterreich, 21, 123-142, 2 Figs., Wien Manuscript received May 5, 1991 Revised manuscript accepted June 15, 1991
