Biometric analyses of Nummulites "ptukhiani" Z.D. Kacharava, 1969 and Nummulites fabianii (Prever in Fabiani, 1905)

Eight populations of microspheric and megalospheric individuals belonging to the species Nummulites ptukhiani (uppermost middle Eocene) and N. fabianii (upper Eocene) from northern Italy, Spain and Romania are described and discriminated biometrically. This distinction permits recognition of the middle/upper Eocene boundary in shallow carbonate platform facies, The name N. ptukhiani as used here applies only to the western European ancestors of N. fabianii, with N. ptukhiani from Armenia being a separate species. In the megalospheric generation, test size, ornamentation, and external form show no direct correlation with geologic age and may have been paleoenvironmentally controlled. On the contrary, the examined B forms of N. ptukhiani are substantially smaller and more inflated than the N, fabianii B forms, Moreover, the ornamentation pattern of N. ptukhiani B (reticulated, granulated) is easily distinguishable from that of N. fabianii B (sinuous to meandering reticulate, non-granulated). For the megalospheric individuals, internal features seem more independent of the paleoenvironment, but they may also have been environmentally controlled in some cases. Four parameters are used to distinguish the A forms: protoconch height, shape of the embryonic apparatus, mean chamber length, and coiling curves. None of these internal features has been found useful to distinguish between the B forms of the two species. Only the total number of whorls is different (two to seven more whorls in N. fabianii B than in N. ptukhiani B). The overall similarities between the two species and the gradual transition of the measured features confirm they are successive chronospecies that can, however, be separated by conventional limits, useful for biostratigraphy of the middle/upper Eocene carbonates of the Tethys

Nummulite biostratigraphy at the Middle/Upper Eocene boundary in the northern Mediterranean area

Some larger foraminifera assemblages (mostly nummulitids) near the Middle/Upper Eocene boundary have been investigated. Sections of the Veneto area (Berici and Lessini Mts., northern Italy) were studied and compared with others of the same age from Spain (Ebro basin) and Romania (Cluj-Napoca). In the Veneto area the results allow to split the upper Middle Eocene Nummulites brongniarti Zone into two biozones: a lower N. lyelli Zone and an upper N. biedai Zone. The N. aff. fabianii Zone is here renamed N. variolarius/incrassatus Zone. This subdivision can also be recognized in Spain and Romania.According to the current conceptions, the base of the Priabonian (= Upper Eocene) could correspond either to the base of the N. fabianii s.s. Zone or to the base of the N. variolarius/incrassatus Zone. Anyway, the Mossano succession could be a potential Global Stratotype Section and Point for the base of the Priabonian

Le pietre, le malte e il degrado della Torre Ghirlandina

L'articolo sintetizza i risultati dello studio geo-paleontologico eseguito sulle pietre del rivestimento della Torre Ghirlandina, dando indicazioni sulla loro natura e provenienza. Inoltre, fornisce informazioni sulle malte usate durante la costruzione e sulla probabile provenienza dei materiali usati per la loro produzione. Infine, tratta della distribuzione del degrado superficiale sul quale il restauro è intervenuto

PALEOENVIRONMENTAL CONTROL ON THE MORPHOLOGY OF NUMMULITES FABIANII (PREVER) IN THE LATE PRIABONIAN PARASEQUENCES OF THE MORTISA SANDSTONE (VENETIAN ALPS, NORTHERN ITALY)

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NUMMULITE BIOSTRATIGRAPHY AT THE MIDDLE/UPPER EOCENE BOUNDARY IN THE NORTHERN MEDITERRANEAN AREA

Some larger  foraminiferal assemblages (mostly nummulitids) near the Middle/Upper Eocene boundary have been investigated. Sections of the Veneto area (Berici and Lessini Mts., northern Italy) were studied and compared with others of the same age from Spain (Ebro basin) and Romania (Cluj-Napoca). In the Veneto area the results allow to split the upper Middle Eocene Nummulites brongniarti Zone into two biozones: a lower N. lyelli Zone and an upper N. biedai Zone. The N. aff. fahianìi Zone is here renamed N. variolarias/incrassatus Zone. This subdivision can also  be recognized in Spain and Romania. According to the current conceptions,  the base of the Priabonian (= Upper Eocene) could correspond either to the base of the N. fabianii s.s. Zone or to the base of the N. vaiolarius/ incrassatas Zone. Anyway, the Mossano succession could be a potential Globai Stratotype Section and Point for the base of the Priabonian

The middle to late Eocene evolution of nummulitid foraminifer Heterostegina in the Western Tethys

Megalospheric forms of Western Tethyan late Bartonian to late Priabonian involute Heterostegina from numerous localities, marking different ecological conditions, were morphometrically investigated. They belong to three species, H. armenica, H. reticulata, and H. gracilis based on the presence/absence of granulation, on the chamberlet characteristics and on the relative size of proloculus. Within these species a very rapid evolution could be observed in the reduction of the number of operculinid chambers, in the increase of the number of chamberlets and partially in the increase of the proloculus size. This evolution is demonstrated by stratigraphic superpositions in several localities (especially in the Mossano section), and is supported also by the change of co−occurring fossils, starting with the disappearance of large−sized Nummulites, then followed by the appearance of the genus Spiroclypeus and then by the disappearance of orthophragmines of middle Eocene acme. Based on the reduction of operculinid chambers, two chronosubspecies of Heterostegina armenica and seven of H. reticulata are defined biometrically (four of them: H. armenica tigrisensis, H. reticulata tronensis, H. r. hungarica, and H. r. mossanensis are introduced here). This allows to subdivide the Shallow Benthic Zone (SBZ) 18 into three and SBZ 19 into two subzones. The extremely rapid evolution of H. reticulata allows to calibrate larger foraminiferal events around the middle/late Eocene boundary. The extinction of large−sized Nummulites seems to be heterochronous in the late Bartonian in having migrated eastward, while the first appearance of Spiroclypeus is shown to be synchronous at the base of the Priabonian. The middle/upper Eocene (=Bartonian/Priabonian) boundary is to be placed at the base of the Priabona marls in the Mossano section corresponding to the SBZ 18/19 limit, to the first appearance of genus Spiroclypeus, to that of Nummulites fabianii and of Heterostegina reticulata mossanensis. It falls into the upper part of both the P15 and NP18 planktic zones. The Western Tethyan Eocene involute Heterostegina became extinct, apparently with no Oligocene successors

Exceptional development of dissepimental coenosteum in the new Eocene scleractinian coral genus Nancygyra (Ypresian, Monte Postale, NE Italy)

In colonial corals, the polyps are interconnected with a common tissue called coenosarc. Polyps and coenosarc secrete distinct skeletal structures: corallites and coenosteum, respectively. Ratio of corallite to coenosteum development may vary resulting in two extreme architectural patterns of coral colonies: corallite-dominated (e.g., cerioid) and coenosteum-dominated (e.g., aphroid) colonies. A large suite of examples of these patterns can be identified among extant and fossil corals, including Paleozoic rugosan corals. Herein we describe the new early Eocene colonial scleractinian coral genus Nancygyra that forms exceptional coenosteum-dominated colonies. The colonies were found in Ypresian limestones at Monte Postale (Lessini Mountains, Veneto, NE Italy), very close to the Pesciara di Bolca Fossil-Lagerstätte, where coralgal buildups have been recently recognised and described. The corallum is massive and consists of corallites of variable size (typically few millimeters in lesser calicular diameter) dispersed and protruding from a very extensive and dense dissepimental coenosteum. The coenosteum forms ca. 60-80% of the corallum volume and is made of vesicular convex dissepiments. The new coral is tentatively assigned to Euphylliidae (known in the fossil record since the Paleocene) whose modern representatives develop similar extensive coenosteum with sticking-out corallites (Galaxea) and form coralla with well-developed walls and thickened axial margins of septa (Euphyllia). Among stratigraphically older scleractinian corals, similar extent of dissepimental coenosteum development is shown by some Mesozoic amphiastreids and rhipidogyriids

La grandiosa rosa di pietra. Analisi litologica del rosone del Duomo di Modena

L'analisi litologica del rosone del Duomo di Modena ha permesso di identificare 5 diversi litotipi: Arenaria della Formazione di Pantano, Arenaria di Scabiazza, Pietra di Aurisina varietà granitello, Rosso Ammonitico e Marmo Proconnesio.Lo studio del rosone ha dimostrato come il Duomo sia l’unico monumento modenese in cui si sia utilizzata pietra locale. Nel contesto della Cattedrale la rosa si contraddistingue in quanto non presenta reimpiego di materiali antichi, come testimoniato nelle fasi precedenti, e nemmeno di Rosso Ammonitico veronese, litotipo principale utilizzato dai Campionesi. L’arenaria impiegata nel rivestimento lapideo esterno si è rivelata del tutto inadeguata, come dimostrato sulla Ghirlandina dalle sostituzioni col Rosso Ammonitico effettuate a partire dal XVI secolo. La pratica del restauro dei materiali degradati è stata affrontata diversamente nel corso dei secoli, e progressivamente si è giunti alla consapevolezza del rispetto dei materiali. Solo alla fine del ‘800, quando vennero condotti i risanamenti sulla Cattedrale, la cultura del restauro impose di impiegare lo stesso materiale nel ricostruire gli elementi danneggiati dal tempo. Una nuova attenzione, specchio della sensibilità artistica del momento storico, ha permesso di conservare questo unicum all’interno del panorama architettonico modenese