Bollcm'no deb Societd Palcontolog'ca Italians 39 (I), 2000 ISSN 0375-7633 29-45 2 pls. Modena, Febbaio 2000
Early Aptian ammonites from the top of the Maiolica and the anoxic "Selli level" (Lombardy, Southern Alps)
Giovanni LANDRA Fabrizio CECCA Zdenek VASICEK Dipartimento di Scienze della Terra UPRESA 6019 De artment of Geolo and Mineralogy Universiti di Milano Universite de Provence, Marseille Rining.~niversiry,%strava-~oruba
KEY WORDS- Ammonoidea, Syrtematics, Biortratipaphy, Palaeoecology, Cretaceour, Aptian, Northern Italy.
ABSTRACT- Thepaper deak with the description o Ea~lyCretaceous ammonitefaunarfrom black shale layers intercalated within thr transition bemeen thcMaiolica limemner and the mark of jheMarne di Bruntino Formation in a quarry nmr Cerana Brianza (Comoprovince, Northern Italyl. For thefirrt time in Italy ammonites have been collected ako in the regionale uivalent ofthe Zivello Selli': companding to the oceanic anowic event OAE la. The ammoniter studied have been mi ed to the Early $tian by meam ofintepated bio- and ma e tormtimaphv... . , In ,fact, ammonite biortrati~anhic.. , markerr are scarce in a af$al~editerranean area such ar the Lombard" barin because noltmun~y,raw ,w rht rn~prz11 inJ rI,t;;,r~ a/ ~i?.q'~i~t..w;h D?o>,~ nlidir ,/I.iinn'ne .~b,~vlr.zr (.&z,I Xn~nrrhm a pzlan,nslz~gi,;rlp~,~nrI, z I, t , tno~ro, thr >nt INTRODUCTION Marche region (Bersezio, 1994). In particular, some ammonites were also collected from within the LSE, The Lower Cretaceous pelagic successions wide- the first Italian ammonite record in this layer. spread in both Northern and Central Italy are The aim of this aper is to describe the ammonite remarkably poor in ammonites, a fact that prevented faunas recently colfected in successive layers, along a comprehensive calibration of both the detailed bio- with the previous findings, from Section C of Cecca stratigraphy based on calcareous and siliceous plank- & Landra (1994), despite the poor preservation of ton and m netostrati raphy to ammonite zones and the specimens and the impoverished character of the stage boun. arles On? y recently, some ammonites assemblages. were found in few sections from the Umbria-Marche basin (central Italy) within the Maiolica Formation, THE "LIVELLO SELLI" AND ITS EQUIVALENTS: which allowed us to place some firm ties such as the GEOGRAPHIC DISTRIBUTION AND AGE. HauterivianlBarremian boundary falling in magnetic chron CM4 (Cecca et al., 1994a). Some ammonites A prominent black horizon was identified at the were also collected (Cecca & Landra, 1994) from two transition between the Maiolica and "Marne a sections exposed in the quarries of Cesana Brianza, Fucoidi" pelagic formations in the Umbria-Marche north of Milan (Southern Alps, Northern Italy)'. The area (Central Italy) by Wezel (1985) and formalized ammonites indicate a late Barremian and possibxan with the name "Livello Selli" by Coccioni et al. earliest. , - ~~ Aptian age, while few ammonites of eaily (1987) as a regional marker-level. In the type area the Apt~anage were recorded in a third nearby section (= "Livello Selli" consists of laminated black shales rich Section C of Cecca & Landra, 1994). in organic matter, alternated with radiolarian silts. Its The Cesana Brianza sections s an the transition thickness ranges from 1 to 3 m and its carbonate con- between the Maiolica and Marue lI Bruntino forma- tent is dose to 0%. The "Selli Level" has been reco tions, which is characterized by the presence of an nized in other areas such as the Belluno Basin (norti: organic-rick black layer, identified as e uivalent of eastern Italy) in the Cismon section (Weissert,l989; the anoxic "Livello Selli" (= LSE) of t'2 e Umbria- Herbert, 1992; Erba & Larson, 1998), the Lombardy 30 G. LANDRA, F CECCA, Z VASICEK Text-fig. 1 - Location ma of the study area an8region- a1 geolo ical setting (above). batted: Qua- ternary sediments of ,the Po Plain; ruled: predominantly igneo- us and metamorphic rocks; plain (in the middle part of the sketch): Permian and Mesozoic sediments; dashed line: approxi- mate limit of Meso- zoic palaeogeo raphic wnes (Trenro flateau and Lombardy Basin). Below, topo ra hic map showing tte Lca- tion of the quarry; the asterisk indicates the studied section. basin at Cesana (Bersezio, 1994), and the Vocontian Bermuda basin, and Ocean Drilling Program Site Basin (southern France), where it was named "Niveau 641 - Galicia Bank), in Southern Atlantic (DSDP Go uel" (Brkhkret, 1988). Sites 364 - Angola basin and 511 - FalMand %he "Livello Selli", with similar lithological fea- Plateau), and in Indian Ocean (ODP Site 738 - tures (Corg- and radiolarian-rich laminated horizon) Exmouth Plateau). occurs in the same stratigraphic position also in the Although most of the localities mentioned above Pacific Ocean (Sliter, 1989) where it was recovered in belong to the Tethyan and oceanic tropical domains, the DSDP (Deep Sea Drillin Project) Sites 463 in analogy with the Austral ocean an equivalent of (Mid Pacific Mountain), 167 ?Magellan Rise), 305 this event seems to be present in the Boreal realm. (Shatsky Rise), and 317 (Manihiki Plateau). Or anic Jenkyns (1980) reported some discontinuous bitumi- rich layers, also called "black shales", are pecu Flar of- nous shales from the Lower Aptian of the North Sea the oceanic domain in mid-Cretaceous reen house" (data from Anderton et aL, 1979) and the Lower time; they occur as discrete layers an'i record the Aptian "Fischschiefer" from the Lower Saxony epeir- Oceanic Anoxic Events (Oms), the oldest of which ic sea (Germany) was suggested to be coeval and was indicated as OAEla by Arthur et al. (1990) and equivalent of the OAEla (Thurow & Mutterlose, coincides with the Selli Level. Bralower et al. (1994) 1993; Bersezio, 1994). The latter correlation, bowev- demonstrated that OAEla is present also in Northern er, is disputed by Kemper (1995), who on the basis of Atlantic (DSDP Sites 402 - Bay of Biscay, 417 - the data from Wiechendorf 1/86 borehole, suggested 4 APTLANAMMONITES FROM MIOLICA RND "SELL1LEVEL" 3 1 a brief heterochrony between the "Fischschiefer" and "Fischschiefer"inW~echendorf1/86 borehole (Cepek, the "Livello Selli", the latter having its time-equiva- 1995), and at the base of the DufreuoyiuJirrcata Zone lent in a higher horizon of the same borehole. (= Tropaeum bowerbanki/Dufenoyia spp. in Moullade The correlation between OAEla and the "Livello et al., 1998) from La Btdoule (SE France). Selli" is supported by bio- and magneto-stratigra hic According to Mutterlose (1992) and Keupp & data. The 'Livello Selli" from the Gorgo a Cer! ara Mutterlose (1994), the "Fischschiefer"~ans the inter- section (Umbria-Marche basin) (Lowrie et aL, 1980; val from the upper part of the Des k' ayesztes forbesi Lowrie & Alvarez, 1984; Channell et al., 1995), or Zone to the lower part of the Deshayesites deshayesi the "Selli equivalent" from the Cismon section and Zone and it is sandwiched by the FOs of the calcare- APTICORE (Belluno Basin, Venetian Southern ous nannofossil Fkzbellites oblongus and Rbagodiscus Alps) (Channell et al., 1995; Erba & Larson, 1998), angustus below and Eprolithus varolii and E. floralis and in the Cesana Brianza section (Lombardy Basin)) above. The FO of R. angustus is recorded at the (Channell et aL, 1995) as well as OAEla equivalents boundary between the D. weissi and D. deshayesi from the Pacific DSDP Sites 167 and 463 (Sliter, Zones at La BCdoule (Moullade etaL, 1988). 1989), all fall in the lower part of the Long All the data point to a late Early Aptian age for the Cretaceous Normal. "Livello Selli" and all the events related to OAEla. In terms of calcareous nannofossil biostratigra hy, (Text-fig. 2) all the "Livello Selli" and Selli equivalents from al f the localities mentioned above, then including the Pacific, DESCRIPTION OF THE STUDIED SECTION Atlantic and Indian oceans, fall in the upper part of the Chiartozygzu litteranus Zone, whose base is better The ammonites were collected from Section C of identified by the first appearance (FO) of Ruciuolithw Cecca & Landra (1994), located in the eastern part of irregularis, and just prior to the FO of Eprolithusflo- the Cesana Brianza quarry (Text-fig. I), that corre- ralis (see Erba, 1996 for a synthesis) (Text-fig. 2). sponds to the succession studied by Bersezio (1993, Concerning planktonic foraminifera1 biostratigra- 1994) and to the section named "Alpetto" by phy, the OAEla and the Selli Levels at the same local- Channell et aL (1995). ltles were attributed to the upper part of the The fossils here described come from a succession Globigerinelloides blowi Zone (Coccioni et aL, 1987; of black-shale beds intercalated between the top of Coccioni et al, 1992; BrChtret & Delamette, 1989; the Maiolica and the base of the Marne di Bruntino Sliter, 1989; Bralower etal, 1994; Weiss, 1995), just formations (Text-fig. 3). More precisely, the below the FO of Leo oldina cabri, which defines the ammonite beds belong to the "transitional facies" rec- base of the Leopol1 zna cabk Zone (Caron, 1985). ognized by Barberis et aL (1992) and subsequently Recent study on the Cismon APTICORE (Premoli studied in detail by Bersezio (1993). The "transition- Silva et aL, 1998; Erba et aL, in press), however, al facies" is characterized by a rhythmic alternation of proved that the Selli Level is entirely comprised in the limestones and mark whose terrigenous fraction Leopoldina cabri Zone, as this taxon a pears just increases upwards. below the Selli in agreement with an earp ler appear- According to Bersezio (1994) the LSE falls ance of Leopoldina cabri within the early Aptian D. between the "transitional facies" and the Marne di weissi Zone in French Vocontian Basin (Ma niez Bruntino Formation; it yielded some ammonites at m Jannin et aL, 1997). It is worth mentioning tiat 39-39.5 (Text-fig. 3). cabri is rare at the beginning of its range and fre- A more detailed lithostratigraphic log than that quently suyected to d,issolu~ion~along with other oresented bv Cecca & Landra (1994) is reoorted in planktonic oramln~fera,that just~fieswhy Moullade Yext-fig. 3. ?he same log was used b; ~haAellet al. et aL (1998) reported the FO of L. cabn only from (1995) during the sam ling for the magnetostrati- the top art of the D. deshayesi Zone in La Btdoule graphic study of their A7 petto section (= our Section section &E France). C). Bersezio (1994) recognized a "lower critical level" Direct correlation between calcareous nannofossil and "upper critical level" (LCL and UCL, respective- events and ammonite zonation indicates that the FO ly) below and above the LSE. These terms were orig- of R. irregularis, equated to the base of the inally introduced by Coccioni et aL (1992) to Chiartozygus litterarius Zone, falls within the latest describe two intervals sandwichin the "Livello Selli" Barremian Martelites sararini ammonite Zone (Cecca and characterized by absent or !epleted planktonic et aL, 1994b; Erba, 1996; Aguado et aL, 1997), and foraminifera in the Gorgo a Cerbara section. In occurs well below the base of the anoxic event at Bersezio (1994) they are informally used to indicate a Cesana Brianza (Erba in Bersezio, 1994; Channell et mere lithological similarity with the Gorgo a Cerbara al, 1995), Gorgo a Cerbara (Coccioni et aL, 1992), critical levels, that are more calcareous than the LSE, and Wiechendorf 1186 borehole (Cepek, 1995). On and do not refer to the palaeontolo ical content. the other hand, the FO of Eprolithwfioralis is record- The ammonites described in tiis paper include ed above the top of the LSE in the Cesana Brianza also those already cited by Cecca & Landra (1994) section (Erba in Bersezio, 1994), above the top of the above metre 9.68. The up-dated faunal list is report- G LANDRA, R CECCA, .Z VASICEK TETHYAN CALCAREOUS AMMONITE L! L! ZONE NANNOFOSSILS Mulo Workshop. 1992 ALB L, tardefurcata H. jacobi ------A. nolani Lo N, steinrnannii F! melchioris E, subnodosocostatum D, furcata F2 2 D. deshayesi D,weissi D, tuarkyricus BAR M,sarasini Text-fig. 2 - Integrated stratigraphy of the Aptian Stage for Tethys and low latitudes (modified after Erba, 1996) ed below in stratigraphic order (the numbers in metre 39.3: Macroscaphites (M.) sp. (I), Pychoceras brackets represent the number of specimens): sp. form 2 (1); - between metre 39-39.5: Eul toceras anisopychum (3), Transitional facies Eulytoceras phestum <2), Lytoceras sp. (5), metre 24.5: Macroscaphites (Costidiscw) sp. (I), gen. Melchiorites cf. melchioris (3), Melchiorites sp. (I), and sp. indet. (3); Ptychoceras cf. meyrati (I), ?Ancyloceras (Audouli- metre 27.5: Phylloceras sp. (1); ceras) cf. fallauxi (I), Ancylocera sp. (1); metre 28.2: gen. and sp. indet. (1); metre 39.5: iytocerasp. (2). metre 30.45: L toreras sp (1) metre 31.1: Si1". esztes sp ;.;(I), SYSTEMATIC DESCRIPTIONS metre 31.2: Pychocerascf. meyrati (I), Silesitesaff. ser- anonis (2), Silesites sp. (2), gen. and sp. indet. (1); We follow the classification of the Cretaceous metre 34.1: Lytoceras sp. (I), ?Costidiscw sp. (I), Ammonoidea by Wright et al. (1996). The standard Melchiorites sp. (2), Silesites aff. jeranonis (lo), dimensions for normally coiled ammonites are given Siksiter sp. (3), Ptychocerasponi (I), Ptychoceras sp. in millimetres and as percentages of the diameter. form 1 (I), Procheloniceras cf. sporadicum (11, The following abbreviations have been used: Leptoceratoides boheneggeri (7), fragments of rep- tile bones, plant debris; D = maximum diameter; metre 34.75-34.80: Macrosca bites (Costidiscw) recti d = diameter at which measurements were taken costatus (1), Ancyloceratide gen. et sp. indet. (2): when less than D; Uw = umbilical width; Livello Selli Equivalent Wh = whorl height; metre 39.1: Lytoceras si: (4), Desmoceratidae gen. et K = number of ribs per whorl (Kl2 per half whorl); sp. indet. (I), Melc zorztes cf. melchioris (1); Concerning uncoiled ammonites the terms used in APTLANRMMONITES FROM MAIOLICA AND "SELL1LEVEr - Stratigraphic log of Section C, Cesa- na Brianza. Le- gend: a) pela ic calc~luntes; %) black shales; c) pelagic calcilu- tites with grey or black cherrs; d) grey or green shales; e) turbidi- tic calcilutites; f) turbiditic calci- sdtites; g) marly calcilutites; h) marls; i) shales at the top of the turbiditic layer; I) slump. Abbrevia- tions: LCL = Lower Critical Level; LSE = "Livello Selli" E uivalenr; UCL =9Upper Critical Level; MBF = Marne di Brunti- no Formation. The numbers of the fassiliferous levels corres ond to the sampP es of Channel1 et al. (1995) studied for magnetostra- tigraphy P G LANDRA, F CECCA, Z VASICEK E the descriptions and abbreviations of the dimension- (K 141) and three ribs in the juvenile form 8242 (K al characters are: 140). H = maximum height of the specimen; Lh = hook lenght; Discusion - The bending of the ribs is less pro- pi Lsl, Ls2 = 1st and 2nd shaft lenght; nounced than in the specimen fi ured as E. phestum g hb = whorl height at the bend; by Kilian 8c Reboul(1915, pl. 1, ig.2). According to 1, hh = whod height at the hook; Vasicek (1972), in E. phestum the number of ribs per hs = whorl height at the shaft. whorl is mainly 40, but it may occasionally vary from 32 to 44. As described by Murphy (1975) the ribs are The poor preservation of our specimens prevent- closely spaced in the late growth stage. In our speci- ed to obtain measurements of the whorl breadth and, mens countin of the ribs on a whole whorl was pre- generally, to observe the sutures. vented and onfy in specimen 8242 (K140) it is possi- The specimens are housed in the "Museo di ble to observe 22 ribs in the last half whorl. E, phes- Paleontologia" of the University of Milan (MPUM), hrm differs from E. ran'cinchrm in having a closer ribs numbers 8218 to 8271, followed in brackets (ex. s acing. Both specimens are internal molds and evi- 8243 (K 141)) by our own numbers. In fact, a Lnce of flares is lacking. MPUM number may include more than one speci- men of the same species, whilst our own numbers Stratigraphic level - Both specimens come from indicate the sin le specimens and are useful to dis- metre 39. tin uish the di 2erent specimens in the measurement tabyes. EUL~CERASANISOP~CHUM (Uhlig, 1883) C~~SSCEPHALOPODAL~~C~,1817 1883 Lytoccrusaniroptychum UHLIG,p. 190, pl. 4, fig. 7; pl. 14, fig. 9. Order AMMONOIDEAZittel, 1884 1883 Lytocerarn. f.? aff. anzropychum UHLIG,p. 190, pl. 4, fig. Suborder L~OCERATINAHyatt, 1889 ".R Superfamily LYTOCERATACEAENeumayr, 1875 1972 Eulytocexar aniroptychum (Uhlig) - VASICEK,p. 39, pl. 2, Family LYTOCERATIDAENeumayr, 1875 fig. 7 (cum syn.). 1994a Eul tocera, aniropvcbum (Uhlig) - CECCAeta/., fig. 5f. Subfamily LYTOCERATINAENeumayr, 1875 1995 ~uLcerusaniioplychum (Uhlig) - AW,pl. 11, fi 12 1998 ~ufroceraraniroptychum (Uhlig) - CECCAet aL, p. 6% pi. Genus EULYTOCERASSpath, 1927 1, igs. 17, 18. qpe species - Ammonites inaequalicostatzu d'Orbi- Matm'al- Three specimens: two internal moulds gny, 1840. 8261 (K 168), 8261 (K 169) and a fragment with its impression 8261 (K 170 a, b). EUYTOCERASPHESTUM (Matheron, 1878) PI. 1, fig. 1 Dimemions (in mm) - specimen D Uw Wh 1878 Ammonites hernu MATHERON,pi. C-20, fig. 5 a-C. 8261 (K 168) 26 10.5 (0.40) 11 (0.41) 1949 L tocerarpR arrm Math. - VUI, p. 42, pl. 1, fig. 3. 8261 (K 169) 13 5.5 (0.42) 4.5 (0.35) 1972 2ulytocerm he~zum(Matheran) - VASICEK,p. 37, pl. 2, fig. 6 (cum synf. 1975 Eulyocrra~phestum(Marheron) - MURPHY,p. 18, pi. 2, Descri tion The shell is evolute and the scul ture is formef by weak ribs. The main feature o! thls. 1995 &/?~mmphernrm (Matheran)-Am, p1.12, fi 1-3 h. s ecies is the alternance of two type of ribs. Two to 1997 ~u$tocerar~heitu,(Matheron) - DELANOY,pl. 3,Ei. 5. t 1ree weak ribs are present between two sli htly thicker ribs, referred by Vasicek (1972) to fares' Material- Two specimens: the internal mould of bases. This feature was observed only in specimen a juvenile shell and its impression 8242 (ti 140) and 8261 (ti 170a) and doubtfully in specimen 8261 (K a fragment 8243 (ti 141). 168). ., Dimensions (in mrn) - specimen D tiw Wh Ki2 Di~cmion- According to ~hlig(1883, p. 190) 8243 (K 141) 14 5.5 (0.39) 5.5 (0.39)- 22 the typical alternance of strong and weak ribs begins t~ . after the diameter of 15 mm. Our specimens are Description - Evolute shell with fine uniform and smaller than those figured by Uhlig (1883) and broadly spaced ribbing. Ribs sim le, continuous, Vasicek (1972) and therefore they 'do not show the shar hut fine; close to the periumbip. ~cal margin they characters of the adults. tento gentli +d backwards. The intenpace between two ri s 1s wide as six ribs in specimen 8243 Stratigraphic level- All specimens from metre 39. APTLANAMMONITES FROM MAIOLICA AND "SELL1LEVEL" 35 Suborder AMMONITINAHyatt, 1889 1960 Si/efite~reranonirOrbi F7 - D~uscHm,pl. 45, figs. 6-8. Superfamily DESMOCERATACEAEZittel, 1895 1995 Silesiter aff. rrnrnonir d Orblgny) - AM, pl. 17, figs. 7- Famil DESMOCERATIDAEZittel, 1895 9. SubLmily PUZOSIINAESpath, 1922 Material - Thirteen s~ecimens.8218 (K 100). Genus MELCHIO~UTESSpath, 1923 Qpe species - Ammonites melchiorisTietze, 1872. MELCHIOFUTEScf. MELCHIORlS (Tietze, 1872) P1. 1, figs. 4, 5 Dimensions (in mm) - specimen D Uw Wh K Material - Four specimens: 8254 (K 162), 8257 8218(K100) 21 7.5 (0.36) 7.5 (0.36) - 8219 (K 101) -24.5 10.5 (0.43) 8.25 (0.34) 33 (K 167), 8257 (K 172), 8260 (K 171). 8220 (K 102) -23 -19 7 (0.36) 7 (0.36) 35 Dimensions (in mm) - 8221 (K 103) 18.5 7 (0.37) 6 (0.32) - specimen D Uw Wh 8218 (K 110) -15 5.5 (0.36) 5.5 (0.36) - 8254 (K 162) 27 7.5 (0.28) 12 (0.44) 8218 (K 112) -17 7.5 (0.44) 5.5 (0.32) - 8257 (K 167) 29 - 8 (0.28) 12 (0.41) 8227 (K 113) 9.5 4 (0.42) 3 (0.315) - 8257 (K 172) 19.5 5 (0.26) 8.5 (0.44) 8238 (K 135) 10 4 (0.40) 3.25 (0.325) - 8239 (K 137) 46 17.5 (0.38) 16 (0.35) - Description - Moderately evolute shells with slightly prorsiradiate constrictions. These be in Description - Evolute shell with numerous fine, straight but above the upper third of the flank t i ey prorsiradiate ribs which are strongly projected on become projected forward. venter. There are generally 3-4 simple ribs per one biplicate rib. The latter branch at the u per third of Discwsion - The specimens studied are compared the flank. Constrictions are wider than tie interspace to M. mehioris (Tietze) (whose ty e specimens and between two ribs: 7 constrictions were observed in further topoty es have been figurel- by Avram, 1978) specimen 8220 (K 102) at D - 23. on the basis oP the shell coiling, the number and the shape of the constrictions. However, their preserva- Discwsion - The specimens described are similar tion does not allow us a more precise determination. to S. seranonis but the smaller umbilicus, the finer rib- bing and the more numerous constrictions in the Stratigra hic level - Specimens 8257 (K 172), majority of the individuals suggest the temporary dis- 8257 (K 1(P 7), 8260 (K 171) from metre 39; speci- tinction of our forms from S. reranonis s. str. The men 8254 (K 162) from metre 39.1. same conclusion has been reached by Avram (1995). Further research will clarify the taxonomic status of this group. Two hypotheses can be made: 1) gradual Material- Two specimens, 8250 (K 156), 8250 evolution of the species S. reranonis with pro ressive increase within the population of individu 8,s w~th (K 163). narrower umbilicus and more numerous constric- Dimensiow (in mm) - tions; 2) actual speciation. In the latter case the spec- specimen D Uw Wh imens described above should be included in a new 8250 (K 156) 34 8.5 (0.25) 15.5 (0.46) species. Dismsion - Fragments of possible Melcbiorites Stratigraphic level- 8238 (K 135), 8239 (K 137) without any preserved character preventing identifi- from metre 31.2; 8218 (K loo), 8218 (K 108), 8218 cation at species level. (K 110), 8218 (K Ill), 8218 (K 112), 8219 (K 101), 8220 (K 102), 8221 (K 103), 8227 (K 113), 8228 (K Stratigraphic leuel- Both specimens from metre 34.1. 114) from metre 34.1; 8251 (K 157) from rubble. Family SILESITIDAEH att, 1900 SILESITESsp. Genus SILESITESLJhCg, 1883 Qpe pecies- Ammonites seranonis d' Orbigny, 1841. Material- Six specimens: 8225 (K 109), 8225 (K 115), 8226 (K 116), 8245 (K 147), 8245 (K 158), SILESITESaff. S. SERANONIS (d' Orbigny, 1841) 8262 (K 174). PI. 1, figs. 6-10 Dimensions (in mm) - parr 1883 Ammoniter najaniTietze - UHUG,p. 234, pl. 18, fig. specimen D Uw Wh 4 only. 8226 (K 116) 13.5 5.5 (0.41) 4.5 (0.33) ? 36 G. LANDRR E CECCA, Z. VASICEK Discussion - The incomplete preservation of these Subgenus AUDOULICERASThomel, 1964 s ecimens prevents the specific identification, afthough they seem to be close to Silesites aff S. sera- qpe .pecies - Ancylocerac audouli Astier, 185 1. nonis. ? ANCYLOCERAS (AUDOULICERAS)cf. FALLAUXI Stratipaphic level - 8262 (K 174) from metre (Uhlig, 1883) 31.1; 8245 (K 147), 8245 (K 158) from metre 31.2; PI. 1, fig. 12 8225 (K 109), 8225 (K 115), 8226 (K 116) from metre 34.1. Material - 8249 (K 154), a crushed fragment coated with oxides. Suborder ANCYLOCERATINAWiedmann, 1966 Superfamily ANCYLOCERATACEAE Gill, 1871 Description - Fragment of a large specimen corre- Family ANCYLOCERATIDAEGill, 1871 sponding to the shaft, whose be inning is ently Subfamily ANCYLOCERATINAE Gill, 1871 arched, crushed on the ventrolaterk. s~de. The r~f7 s are fine and regularly spaced. Genus ANcYLocERAS d'orbigny, 1842 Discussion - The attribution to Audoulicera fa& qpe species - Anrylocerac matheronianum d'Orbi- bwci is uncertain because the specimen is too incom- gny, 1842. plete. However, it shows strong similarities with the specimen figured by Uhlig (1883, pl. 29, fig. 1) that ? ANCYLOCERAS sp. is characterized by the resence of tuberculated ribs in PI. 1, fig. 11 the initial whorls ofti e young, spiralate stage. The tubercles soon disap ear and the sculpture remains Material- 8241 (K 139), a fragment crushed lat- made of fine, regularf y spaced, simple ribs. erally and coated with oxides. Stratigraphic level- Metre 39. Description - Fragment of the initial, uncoiled, part of the shell and the whorl height rapidly ANCYLOCERATIDAE gen. et sp. indet. sculpture is made of fine, secondary ribs intercalated Material- 8229 (K118), a crushed fragment coat- mary ribs. Four secondaries exist between two pri- ed with oxides. maries. Three tubercles are present on each primary. Description - A small fragment of a gently arched Discussion - The incomplete reservation of this shaft. The whod height increases rapidly. The sculp- specimen makes difficult a reliabP e speclfic determi- ture is made of dense, simple ribs; interspaces about nation. Some morphologic similarities with Ancylo- as wide as ribs. cerassp. figured by Delanoy (1997, pl. 7, fig. 2) from the Deshayesites weissi Zone of the Angles area (SE Discussion - The ribbin of this fragment recalls France) were observed. that of specimen 8249 (% 154), determined as ?Audoulicerascf. fallauxi (Uhlig). However, we cannot Stratigraphic level- Metre 39. ascribe it to this species because of the incomplete EXPLANATION OF PLATE 1 Fig. 1 - Eulytocerarphestum (Matheron). Cesana Brianza, Section C, m 39. N. 8243 (K141); x 1. Fig. 2 - Coiridircur recticortatur (d'orhigny). Cesana Brianza, Section C, m 34.75. N. 8236 (K128); x 1. Fig. 3 - Mammaphitersp.Cesana Brianza, Section C, m 39.3. N. 8247 (K149); x 1. Fig. 4 - Melchioritescf. melchioris (Tietze). Cesana Brianza, Section C, m 39.1. N. 8254 (K162); x 1. Fig. 5 - Melchiorites cf. melchiorir (Tietze). Cesana Brianza, Section C, m 39. N. 8260 (K171); x 1. Fig. 6 - Sileriter aff. ieranonir (d'orbigny). Cesana Brianza, Section C, m 34.1. N. 8219 (K101); x 1. F,g. 7 - Sileriter aff'feranonir(d'orbigny). Cesana Brianza, Section C, m 34.1. N, 8221 (K103); x 1. Fig. 8 a, b - Sileriter a.,reranonis (d'Orbigny). Cesana Brianza, Section C, m 31.2. N. 8239 (K137); x 1: a) internal mold; b) impres- sion. Fig. 9 - SileritesaE ieranonir (d'Orbigny). ~es&aBrianza, Section C, m 34.1. N. 8227 (K113); x 1. Fig. 10 a, b - Silcriter & reranonis (d'orbigny). Cesana Brianza, Section C, m 34.1. N. 8220 (K102); x 1: a) internal mold; b) impres- sion. Fig. 11 - Ancylocerarsp. Cesana Brianza, Section C, m 39. N. 8241 (K 139); x 1. Fig. 12 - ?Ancylocerar (Audoulicerar) ccf.faNawci (Uhlig). Cesana Brianza, Section C, m 39. N. 8249 (K154); x I. I 38 G. LANDRA, F CECOL Z VASICEK i preservation and lack of diagnostic features. shells are characterized by distant ribs bearing mar- , Furthermore, the size of A. fallawci is far larger. ginal thickenings at their ventrolateral ends. This character recalls L. hoheneggeri in the stage of growth Stratigraphic kvel- Metre 34.8. that preceeds the development of constrictions, i. e., the last part of the body chamber of fully grown spec- I Subfamily LEPTOCERATOIDINAEThieuloy, 1966 imens. According to the more recent findings in the i Genus LEPTOCERATOIDESThieuloy, 1966 Lower Barremian of the Silesian Unit (Vasicek & I Klajmon, 1998), the genus kkrstenrceras includes ljpe species - Crioceras (Lqtocw)pumilum Uhlig, only the trochospiral coiled shells with irregular mar- 1883. ginal tubercles. The planispiral shells without tuber- cles or with the regular marginal tubercles on each rib should be included in the genus Leptoceratoides. The LEPTOCERATOIDESHOHENEGGEN (Vasicek & juvenile whorls of some species of Imerites can devel- Wiedmann, 1994) op similar ribbint However, the embryonal part of PI. 2, figs. 1-4 Imerites shows a el~co~dalcoiling and at the same 1994 Karitrnic~rarhohenegeri VASICEK& WIEDMANN,p. 215, diameter its whorls are higher. Unfortunately this pl. 2, fig. 9; pl. 3, figs. 1-3; text-fig. 3 C-D (cum ryn.) stage is not preserved in our material. Furthermore, Imerites bears ventral furrow but this character cannot Material- Seven crushed specimens whose sculp- be observed on our specimens. ture is imperfectly preserved: 8224 (K 107), 8232 (K The detailed stratigraphic position of the_type 121), 8233 (K 122), 8233 (K 123), 8233 (K 125), material of the Silesian Unit is unknown. The speci- 8234 (K 126), 8235 (K 127). All the specimens are mens collected by W. Kuhnt in the Breggia Gorge observable on one side only. Both the ventral area and (Southern Alps, Switzerland) are of Late Barremian the embryonal part of the shells are not visible. age (Vasicek & Wiedmann, 1994). The material from Italy with the associated ammonites indicates the Dimensions (in mm) - interval straddling the BarremianIAptian boundary. specimen D Uw Wh K 8224 (K 107) i6 11.5 (0.44) 8.5 (0.33) 19 Stratzgraphic leuel - All specimens from metre i 8232 (K 121) 19.5 10 (0.51) 7 (0.36) 19 34.1. 8233 (K 122) 16 5.5 (0.34) 8233 (K 125) 18 7 i0.39) 6.5 (0.36) w2-9 8234 (K 126) 17.5 7.25 (0.41) 6.5 (0.37) 18 Family PTYCHOCERATIDAEMeek, 1876 Descrr - Small, planispiral shells with crio- Genus PTYCHOCERASd'orbigny, 1842 cone coi mg They bear relative rare simple, distant (interspaces as wide as two ribs), elevated ribs with ljpe species - Ptychoceras emericianum d'orhigny, marginal thickening. The largest shell reaches the 1842. I diameter of 26 mm. The suture-line is not preserved. Wrip (?n,Wrjght et ai, 1996) has newly pro- Discwsion -The described shells have a relatively posed t e dlst~nct~onof Ptychoceras from Eup cho t small diameter that might indicate the lack of the ceras on the basis of very poor morphologic Jffer; body chamber or, alternative1 their juvenile stage of ences. According to the opinion already expressed by growth. However, the lack of' preserved sutures does two of us (Cecca & Landra, 1994), we keep on con- not allow us to confirm any of the hypotheses. The sidering the latter a mere synonym of the former. WLANATION OF PLATE 2 Fig. Leptocrratoidrr hohnzegge~i(Vasicek & Wiedmann). Cesana Brianza, Section C, m 34.1. N. 8224 (K 107): a) x 2; b) x 1. Fig. Leptoceratoider hohenegeri (Vasicek 81 Wiedmann). Cesana Brianza, Section C, m 34.1. N. 8234 (K 126): a) x 2; b) x 1. Fig. Leptoceratoidc~hohenegeri (Vasicek & Wiedmann): Cesana Brianza, Section C, m 34.1. N. 8235 (K 127): a) x 2; b) x 1. Fig. Leptoceratoider hohenegeri (Vasicek & Wiedmann). Cesana Brianza, Section C, m 34.1. N. 8232 (K 121): a) x 2; b) x 1. Fig. ptvchocemrponi (Simionescu). Cesana Brianza, Section C, m 34.1. N. 8222 (K105); x 1: a) internal mold coated with ammonium chloride; b) internal mold nor coated; c) impression nor coated. Pqchocrrarcf. myati (Ooster). Cesana Brianza, Section C, m 31.2. N.8240 (K138); r 1: a) internal mold; b) impres- sion on the sediment. . .. . Fig. ptvchocera cf. m ati (Ooster). Cesana Brianza, Section C, m 39. N. 8263 (K175); x 1. Fig. ~rochrlonicerac~~oradicum(Rauchadze). Cesana Brianza, Section C, m 34.1. N. 8231 (K 120); x 1. : >:, :ECCA, Z VASICEK PTYCHOCERASPONI Simionescu, 1898 Landra, 1994). Its resence in the Lower Aptian has PI. 2, fig. 5 been also reported 1y Braga et a1 (1982). 1898 ~C~OC~~~~~O~~SIMIONESCU,p. 65, pl. 1, fig. 12 Stratigraphic level- Specimen 8240 (K 138) from metre 31.2; specimen 8263 (K 175) from metre 39. Material - One internal mould and its cast par- tially coated with oxides 8222 (K 105). PTYCHOCERASsp. (form 1) Dimensions (in mm) - Material- 8223 (K106). spec~rnen Lsl hsl hbl Ls2 hs2 hh2 Ls3 hs3 8222 (K105) 16 2.25 - 32.5 3.75 5.5 15.5 4.5 Description - Incomplete s ecimen with the bend Descr~: - This heteromorph shell presents and fragments of two paralle i' shafts preserved for a three sha s the first shaft is in contact with the sec- length of 10 mm. The shell is smooth. ond one and its length is about half of the second. The third shaft is not in contact, although very dose, Discusion - This specimen can be considered with the second. The second bend bears a constric- close to Ptycbocerar minimum Rouchadze because of tion followed by an adoral swollen margin. The first its small size and the lack of sculpture. The ratio shaft and most of the second shaft are smooth, where- between the length of the two shafts of ours ecimen as simple, weak, closely s aced ribs appear (inter- is similar to I? minimum, but its size is slightP y larger spaces about as wide as rib$ on both the last 10 mm and a constriction occurs on the bend. This last char- of the second shaft and the third shaft. acter is absent in the type-specimens described by Rouchadze (1933). Simionescu (1900, p. 11) descri- Dzscumon -This specimen shows some morpho- bed a furrow near the bend of some French specimens logic affinities with I? emerici (d'orbigny) figured by that he ascribed to his species Ptycbocerar inornatum Avrarn (1976, pl. 2, fi . 8), although the presence of Simionescu, although the holotype lacks this charac- a constriction in the %end between the two shafts ter (Simionescu, 1898). P. inornatum is also charac- makes this specimen closer to Ptycboceras ponz terized by a far larger size than our specimen and is Simionescu. described from Hauterivian levels and doubtfully from Barremian ones. Stratigraphic level- Metre 34.1. Stratigraphic level- Metre 34.1. ~YCHOCERAScf. MEYRATI Ooster, 1860 PI. 2, figs. 6, 7 Family MACROSCAPHITIDAEHyatt, 1900 Material- 8240 (K 138), 8263 (K 175). Genus MACROSCAPHITESMeek, 1876 Dimenszons (in mm) - qpe species - Scapbites yvani Puzos, 1831. spmmen Lsl hsl hbl Ls2 hs2 hb2 Ls3 hs3 I 8240 (K 138) -58 -5 - -90 -7 - - -7 8269 (K 175) - - -5 - Costidism Uhlig has been treated as a synonym of Macroscaphites Meek by Wright (in Wright et al, Desm tion Shell characterized by three straight 1996), who formalized Avram's (1984) conclusions shafts. T2 e first- and the second shaft are in contact on dimorphism of this pair from the nornenclatorial except for the area near the bending, the third shaft is point of view. The former is considered the macro- in contact with the second for the first 25 mm then conch, the latter the microconch. However, as also it sli hdy overlaps the first one. The last part of the stressed by Avrarn (1984), it is difficult to arrange all ihirjshaft is missing. The shdl is smooth and no evi- the different Macroscaphites and Costidiscw morphb:. '' dence of scul ture has been observed. Specimen 8263 species in dimorphic pairs corresponding to bio og~ (K 175) has ieen interpreted as corresponding to the cal species. Therefore, we maintain these forms as a first two shafts. discrete taxa ronsiderin Costidism as a subgenus. .This taxonomic approacf. 1s common in Jurassic am- Discussion - Specimen K 138 closely resembles I? ' monites (Zeiss, 1968; Callomon, 1969; Westermann, meyratz described from an Upper Barremian level of 1989). the same quarry (Cecca & Landra, 1994); the two specimens also share the same dimensions. The ridges MACROSCAPHITES(M.) sp. on the third shaft are not evident. Pychoceras meyratz PI. 1, fig. 3 is a long-ranging species recorded from Lower Hauterivian to Upper Barremian levels (Cecca & Material- A crushed fragment 8247 (K 149). APTIANAMMONITES FROM MAIOLICA AND 'TELL1 LEWr 41 Descri tion The s ecimen corres onds to a frag- Discussion - Two specimens are ascribed to this ment oft I? e last part o !the shaft and tie beginning of enus but they could not be identified at specific the bend of a heteromorph ammonite. The ribs are kvel. Only the specimen 8244 (K 142) shows some fine, sharp, s aced and rorsiradiate on the shaft, affinities with C. recticostanrr. radial on the %end. A raiial constriction marks the end of the bend. Stratigraphic level - 8244 (K 142) from metre 24.5; 8256 (K 166) from metre 34.1. Discussion - The fragment can be ascribed to the enus Macrosca bites because morphologically similar Superfamily DOLMLLEICERATACEAEParona & %endsand shaR s of Anahamulina or Hamulina bear Bonarelli, 1897 differently shaped ribs. It is impossible to identify the Family DOLMLLEICERATIDAEParona & Bonarelli, species because the distinctive s ecific characters are 1897 usually develo ed in the normaiy coiled part of the Subfamily CHELONICERATINAESpath, 1923 shell which is Packing in our specimen. Genus PROCHELONICERASSpath, 1923 Stratigraphic level- Metre 39.3. Type rpecies - Ammonites stobieckii d'orbigny, 1850. Subgenus COSTIDISCUSUhlig, 1883 PROCHELONICERAScf. SPORADICUM (Rouchadze, 1933) Type species - Ammonites recticostutus d'orbigny, PI. 2, fig. 8 1841. Material- 8231 (K120), internal mould. MACROSCAPHITES(COSTIDISCUS) RECTICOSTATUS Dimensions (in mm) - specimen D Uw Wh W2 8231 (K 120) 55 27.5 (0.5) 15 (0.27) 21 1841 Ammonite rcctico~talusd'O~sl~m,134, pl. 40, figs. 3,4. Description - Evolute shell with the sculpture 1994 Costidiscur rectimrtarw (d'Orbi $-CECCA 81 LANDRA, characterized by simple, prominent and regularly p. 403, pl. 1, figs. 1,2 (cum n? spaced ribs bearing two rows of tubercles. The inter- 1994 costidiscur rrcticortam (d'orfigny)-. - VASICEK~tal., p. 55, nal whorls are not visible; however, up to d-35 mm it pL 21, fig. 4. 1995a Costidism ~~cticostilm(d'orbigny) - DELANOY,pl. 6, fi 5 is possible to observe lateral, rather strong, tubercles 1995 Costidiscur rectico~tancr(d'orbigny) - CECCAet aL, pf 3; located at the up er third of the flank. Then they dis- ti 14 appear and the ri! s develop a tubercle-like thickening 1995-..- 8xtidk-ur recticortam (d'orbigny) - AM, pl. 12, fig. at the ventrolateral margin. A less pronounced, peri- 10; pl. 13, fig. 1. 1995b Cmtidism r~aco~tam(d'Orbigny)- DELANOY, pl. 5,'fig.4. umbilical, row of tubercles a pears in the reserved 1997 Cmtidim mcticmtam (d'orbigny) - DELANOY,pl. 4, fig. portion of the last whorl an1. it moves slow7. y h~gher 1; pl. 5, fig. 4. on the flank as the relief of the tubercle increases. Material- 8236 (K 128), crushed specimen. Discussion -The specimen bears a higher number of ribs per whorl than all the other species of this genus. The only s ecies showing some mor hologic Dimensions (in mm) - specimen D Uw Wh K similarities is Proci elontcerzs sparadicum. In fact, our 8236 (K 128) 32 8 (0.25) 48 s ecimen could be comparable to the inner whorls of t k e holotype (Rouchadze, 1933, p. 192, pl. 3, fig. 3) ~iscwsion- The specimen shows the typical char- that are unfortunately oorly resented., acters of this species. The presence of constrictions Spinomioceras uma8. ez (Uh r.. lg), a species reported has been already discussed by Cecca & Landra (1994, from the latest Barremian Mu~telitessarasini Zone' 404): even in older, Late Barremian, specimens (Delanoy, 1992, 1995 b), shows some morphologic Lorn northern Italy constrictions are constantly pre- similarities with our specimen, although its ribs are sent. stronger andmo~espaced. . ~. Unfortunately our Epecimen does not bear any trace of suture. Accordingro Delanoy (1992, p. 80), Stratigraphic level- Metre 34.75. the distinction between the genera Procbeloniceras and Spinocriocerasis~~baseJon sutural characters, i. e., MACROSWHITES(COSTIDISCUS) sp. the former bears the 1st lateral saddle higher than the second.one. '. :. Material - Specimens 8244 (K 142), 8256 (K .. . 166). Stratigraphic leuel - Metre 34.1. 42 G. LANDRA, E CECCA, Z VASICEK 23 (see Text-fig. 3). Although there are no direct cor- relations between chron CMO and ammonite bio- Within the described fauna no zonal markers zones, a Deshayesitidae was found in the reversed occur and the biostratigra hic assignment of the sam- interval of chron CMO of the Gorgo a Cerbara section pled levels can be indirect? y stated on the basis of the (Marche Apennines, Central Italy). The previous data obtained with other stratigraphic methods and assignement of this specimen to the genus Prodeshaye- from the literature. The Mediterranean ammonite sites (Cecca et aL, 1995) was questioned (Rawson, assemblages show a remarkable stability during the pers. comm. to F. C., September 1995; Aguado et al, Barremian - Aptian transition (Bra et aL, 1982; 1997); after re-examination it should be identified as Ceca & Landra, 1994; Aguado et ar1997). Deshayesites sp., thus indicating an Early Aptian age. The scarcity in the Mediterranean areas of re re Moreover, most of the ammonitiferous levels of sentatives of the family Deshayesitidae, whict' 1s,- Section C are stratigraphically higher than metre 23 abundant in Boreal areas or in Peri-Tethyan epiconti- and fall within the normal interval above magnetic nental platforms (e. g., Turkmenistan), makes the chron CMO (Text-fip.- 2). We conclude that their aee identification of the BarremianIAptian boundary is Early Aptian. - problematic. This has been stressed recently b The ammonite fauna from metre 39.1 to 39.5 Aguado etal. (1997, p. 316), who also noted the diz belongs to the LSE and some further consideration ficulties to recognize the Early Aptian D. markyricus can be added. In Section C (1) the global nannoconid and D. weissi Zones. In fact, these authors have stud- crisis (Erba, 1994) is doc;kentFd below LSE, at ied a very rich fauna of approximately. . 3500 speci- about metre 36 (Channel1 et aL, 1995) (see Text-fig. mcns and only one specimen of ~lesha~spsir~sis report- 3). This event is 260 kyr younger than the top of ed from the beds presumably corresponding. to the D. chron CMO (Erba, 1996, fig. 5) and probably occurs tuar rzcw Zone. above the ammonite-bearin levels of the D. weissi Tt e Early Aptian age of our fauna could be sub- Zone studied by Aguado eta!, (1997, p. 319); (2) the jected to criticism because Ptychocerm meyrati is a FO of E. floralis is recorded about 6 metres above the long-ranging species, and Audoulicerm is mainly top of LSE in the overlying Marne di Bruntino Fm. recorded in the Upper Barremian (Delanoy, 1992, (Erba in Bersezio, 1994). According to Keupp & 1995b), although its vertical range reaches the D. Mutterlose (1994) the latter datum occurs in the weissi Zone (Delanoy, 1997). The fragment deter- ammonite D. deshayesi Zone, whilst Moullade et a1 mined as Ancylocerm sp. (PI. 1, fi 11) resembles the (1998) reco nized it higher, at the base of the specimen of the D. weissi Zone Figured by Delanoy ~u~en~iaffrcataZone. These data indicate for the (1997, pl. 7, fig. 2). The genus Prochelonicerm indi- LSE an age ranging from the D. weisri to the D. cates the Early Aptian but the characters of the deshayesi Zone (see Text-fig. 2). suture-line are necessa to distinguish it from the morphologically simi7 ar Spznocrroceras of Late I'AIAFOHIOC;EOC;KWl1ICAL AND Barremian age (Delanoy, 1992; Aguado etaL, 1997); I'Al.At0t:(101 C)C;ICAI KI:%IAKK5 the suture-lines are not preserved in the specimen that we have tentatively identified as P. cf. po- The most obvious question arising from the dis- radicum. The range of Silesites seranonis spans from cussion above is why the latest Barremian and Early the Upper Barremian to the Lower Aptian, but the Aptian age-dia nostic taxa, such Heteroceratidae, s ecimens of Szlesztes found in the studied levels prob- Kutatissites, Des51 ayesztes, Cheloniceras, etc. are absent ag ly belong to a new species. Similar specimens have in our area. We believe that both palaeobiogeograph- been assigned to the Late Barremian by Avram (1995) ic and alaeoecologic factors controlled the composi- and b Druschits (1960), although Uhlig's (1883, pl. tion oP the faunal assembla e 18, &. 4) specimen come from the locality of Although less frequent in the epicontinental Malenowice (= Mallenowitz in Uhlig, 1883) where seas of Europe and Central Asia, the taxa mentioned numerous Early Aptian species were collected. The above occur in deep-basin successions of southern type-sppimens of Melchiorites melchioris are of Late Spain and southern France (Aguado et al., 1997; Barremian age (Avram, 1978), but variants of Early Delanoy et aL, 1997). According to the alaeogeo- Aptian age also exist. However, the preservation of raphic reconstructions, the Lombardy gasin was our s ecimens is not sufficient to distinguish the kcated in the Mediterranean Teth s in a more distal morpi, olo ical characters of the different variants. area far from the European an d'.African margins ~evertkeless,in our section (1) E. Erba (in Ceca (Winterer & Bosellini, 1981; Wieczorek, 1988). & Landra, 1994) recognized the FO of the calcareous In southern Spain and southern France the Aptian nannofossil R ire laris at metre 2.95: this event has ammonite assemblages are ically Mediterranean been recorded wi ti? in the ammonite M. sarmini Zone (Cecca, 1998). The faunas coT lected in our section (Cecca et aL, 1994b; Aguado et aL, 1997); and (2) contain Mediterranean taxa only and are character- Channell et aL (1995) recognized the base of the ized by the dominance of long-ranging species. The reversed chron CMO at metre 4.5 and the top at metre absence of other Mediterranean taxa, particularly the APTWAMMONITES FROM 'MAIOUCA AND "SELLI LEVEL" 43 short-lived ;ge-diagnostic ones, leads us to define our boundary in the Betic Cordillera, southern Spain: fauna as an ~mpover~shedMediterranean fauna". Cretaceous Research, 18: 309-329, London. The resulting stability of the ammonite assem- ANDERTON,R., BRIDGES,l? H., LEEDER,M. R. & SELLWOOD,B. W., 1979, A dinamic Stratigraphy of the British Isles: Allen bla es around the BarremianIAptian transition is & Unwin, London: 301 pp. pro ably related to adaptation to distal, epioceanic % ARTHUR,M.A., JENKYNS,H.C., BRUMSACK,H.J., & SCHLANGER environments. These were more stable than the epi- S.O., 1990, Stratigra hy geochemistry and paleaceanogra- continental seas because they were not affected by phy of organic cargo;-rich Cretaceous sequences. In sea-level fluctuations. Ginsburg, R.N. & Beaudoin, B. (eds.), Cretaceous Almost all fossiliferous levels of our section are resources, events and rhythms: NATO AS1 Series C, Kluwer dark, or black, shales particularly those of the equi- Academic Publishers: 75-1 19, Norwell, Massachussecs. Aw,E., 1976, Les fossiles du flysch eocretace et des calcaires valent of the "Livello Selli". Taking into account the tithoniques des hautes vallees de la Doftana et du Titlung s eculations on supposed ammonite life-habitats, the (Carpates orientales): Mem. Inst. Geol. Geophys., 24: 5-73, gmersal forms, feeding on sea-bottoms, should be Bucuresti. very rare or even absent in the anoxic levels (Batt, -, 1978, Observations sur les espkes d'ammonites de la re ion 1993). The majori of the taxa recorded in our sec- de Svinita (Banat) decrites par Tiem (1872) et &lig tion had an epipe7. aglc mode of life: in particular (1883): Dari de seama ale sedint., 64 (3) (1976-1977): 9-25, Lytoceratina, Phylloceratina, Ancyloceratidae and Bucuresti. Pycbocerm probably were vertical migrants in the -, 1984, Correspondent s ecies of the genera Marrofca hitrr Meek and Cortidi~m&lig: Univ. Bucharest, Lab. ~dont. water column (Westermann, 1996). Vasicek & spec. vol., 75 years: 67-80, Bucuresti. Wiedmann (1994) already noted that the biotope of - 1995, Lower Cretaceous (Valanginian-Early Aptian) the Leptoceratoidinae subfamily was close to stag- ammonite succession in the Svinita r ion (SW Rumania). nant, poorly oxygenated environments where they In Bulot, L., Ar ot, M. & ~rnau7H. (eds.), Lawer usual1 occur concentrated in "nests", dominating the Cretaceous cephJo od biostratigraphy of the Western faundspectrum. This has been recently interpreted as Tethys: recent devef opments, regional synthesis and out- standing problems: Geologie Alpine, 1994, MCm. H.S. 20: an opportunistic behaviour in unfavourable environ- 113-167, Grenoble. ments (Cecca, 1998). Nothing can be said about the BARBERIS,A,, FOSSA~,S., BERSEZIO,R. & ERBA,E., 1992, mode of life of Melcbiorites and Szlesztes. The former Lithastratigraphy and biostratigraphy of the Maiolica belongs to the family Desmoceratidae, whose highest Formation from the Lombardy basin (Southern Alps): frequencies are recorded in marly, deep successions Mem. Soc. Geol. It., 45 (1990): 111-1 17,Roma. (Cecca, 1998). The latter is abundant (and even BAIT, R.J., 1993, Ammonite morphotypes as indicators of oxy- dominant in some beds) in deep successions of the genation in a Cretaceous epicontinental sea: Lethaia, 26: 49- Adria microplate, both in calcareous and shal facies 63, Oslo. BERSEZIO,R., 1993, Sedimentary events and rhythms in an Early Probably these taxa also lived in the water coLmn. ' Cretaceous pelagic environment: the Maiolica Fm. of the In summary, most of the ammonites represented Lombard Basin (Southern Alps): Giorn. Geol., s. 3, 55 (1): in the studied levels were not constrained to sea-bot- 5-20, ~oi~na. toms, their feeding habits being probably related to -, 1994, Stratigraphic framework and sedimentary features of the lank ton living in the water column (Cecca, the Lower Aptian "Livella Selli" in the Lombardy Basin 1997, 1998). According to Batt (1993), the ammo- (Southern Alps, Northern Italy): Riv. It. Paleont. Strat., 99 nite shell morphotypes represented in the fossil (4) (1993): 569-589, Milano. assemblage provide a tool in interpreting fluctuations BRAGA,J.C., COMPANY,M., LINARES,A,, RIVAS,P. & SANDOVAL, J., 1982, Conrribucion & la bioestratigrafia del Aptiense de in oxygen levels in marine deposits. On the basis of las Cordilleras Beticas: Cuad. Geol. Iberica, 8: 691-701, the ammonite morphoty es found at Cesana Brianza, Madrid. the anoxic watermass dl.‘! not reach the upper part of BRALOWR,T.J., ARTHUR,MA., LECKIE,R.M., SLITER,W.V., the water column but was close to the bottom. ALLARD, D.J. & SCHLANGER,S.O., 1994, Timing and pale- oceanography of Oceanic D soxialhaxia in the Late AKNOWLEDGEMENTS Barremian to Early'. Aptian (Earr y Cretaceous): Pdaios, 9 (4): 335-369, Lawrence. The authors are deeply indebted to I. Premoli Silva and E. BK~H~RET,J., 1988, Episodes de s6dimentatioi riche en matiere Erba (Milano) far continuous help and stimulating advices, the organique dans les marnes bleues d'age a tien et albien de la text has much benefited their su&estions. partie pelagique du bassin Vocontien: B~~.~s~~.Geol. Ft., 4: H.G. Owen (London), I? Hoedemaeker (Leiden) and a third 349-356, Paris. anonymous referee are thanked for careful reading and con- -, & DELAMETTE,M., 1989, Faunal fluctuation related to structive criticism. G. Chiodi (Milano) printed the photo ra hs oceanographic changes in the Vocontian basin (S-E France) - - This work is supported by C.N.R (Consiglio Nazion Ji.e elle during Aptian-Albian rimes: Geobios, Mem. spec., 11: 267- Ricerche) Gruppo Palaeopelagos - Sottoprogetto Stratigrafia 277, Lyon. Inregrata del Ctetacico Pelagica (IPS). CALLOMON,J.H., 1969, Dimorphism in ammonoidea. Some reflections. In Westermann, G.E.G. (ed.), Sexual dimor- REFERENCES phism in fossil metazoa and taxonomic implications: International Union of Geological Sciences, set. A; 1: 111- AGU~O,R., COMPANY,M., SANDOVAL,J. & TAVERA,J. M., 125, Schw&izerb&tiche,Stungart. 1997, Biostratigrzphic events at the BarremianlAptian CARON,M., 1985, Cretaceod planktic forahinifera. In Bolli, 44 G. LANDR4, I? 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