Giovanni Giuseppe Scanu

European Jurassic floras: statistics and palaeoenvironmental proxies

Abstract The Jurassic floras of Europe show considerable diversity. To examine the extent of this diversity and its possible causes we used multivariate statistical methods (cluster analysis, PCA, NMDS) to compare all significant Jurassic floras in Europe. Data were based on 770 taxa from 46 fossiliferous occurrences (25 units) from France, Germany, Greenland, Hungary, Italy, Norway, Poland, Romania, Scotland, Serbia, Sweden, Switzerland, and the United Kingdom. Statistical analyses were applied at species level and genus level, and also performed for the major plant groups. The genus cladograms show affinities between different localities based on environmental factors, while the cladograms based on species affinities indicate only taxonomical correlations. The study shows that locality age does not seem to be of paramount importance for floral composition.

The Jurassic plant fossils of the Lovisato Collection: preliminary notes

A preliminary account is presented herein of the revision of 473 slabs containing macrofossil plant remains from the Domenico Lovisato plant Collection. The latter is housed in the Museo Sardo di Geologia e Paleontologia “D. Lovisato” of the Università di Cagliari. The material examined encompasses palaeobotanical remains collected from the Genna Selole Formation and from the basal part of the Dorgali Formation, both of Jurassic age at a variety of localities in Barbagia and Sarcidano, eastern Sardinia. A reconstruction is given of the history of the collection, initiated in 1888, and the scientific studies of the flora by a variety of palaeobotanists. Based on a preliminary revision of the specimens the following genera are recognized: Phlebopteris Brongniart, 1836, Hausmannia Dunker, 1846, Coniopteris Brongniart, 1849, Cladophlebis Brongniart, 1849, Sagenopteris Presl in Sternberg, 1838, Cycadeospermum Saporta, 1875, Ptilophyllum Morris in Grant, 1840, Williamsonia Carruthers, 1870 emend. Harris, 1969, Weltrichia Braun, 1847 emend. Harris, 1969, Taeniopteris Brongniart, 1828, Czekanowskia Heer, 1876 emend. Harris et al., 1974, Brachyphyllum Brongniart, 1828, Elatocladus Halle, 1913 emend. Harris, 1979 and Carpolithes Brongniart, 1822. Some plant remains have been putatively assigned to the following genera: Ptilozamites Nathorst, 1878 emend. Antevs, 1914, Nilssonia Brongniart, 1825, Pterophyllum Brongniart, 1828 and Geinitzia Endlicher, 1847. Several of these genera are known also from the Jurassic flora of Yorkshire and from other Jurassic floras of Italy. RIASSUNTO [La flora giurassica della Collezione Lovisato: nota preliminare] In questo lavoro vengono presentati i dati preliminari della revisione sistematica di 473 reperti contenenti resti macroscopici di piante fossili della Collezione Lovisato, conservata presso il Museo di Geologia e Paleontologia Domenico Lovisato, dell’Università degli Studi di Cagliari. La collezione comprende resti fossili raccolti in diverse località del Sarcidano e della Barbagia, nella Sardegna orientale, e provenienti dalla Formazione di Genna Selole e dalla porzione basale della Formazione di Dorgali, entrambe di età medio giurassica. Viene ricostruita la storia della collezione e degli studi effettuati su di essa dai vari studiosi che si sono succeduti nel tempo, a partire dal 1888, anno di inizio delle raccolte e dei campionamenti da parte del Prof. Domenico Lovisato. La revisione tassonomica preliminare consente di fornire una lista aggiornata a livello generico delle forme riconosciute nella collezione, che sono: Phlebopteris Brongniart, 1836, Hausmannia Dunker, 1846, Coniopteris Brongniart, 1849, Cladophlebis Brongniart, 1849, Sagenopteris Presl in Sternberg, 1838, Cycadeospermum Saporta, 1875, Ptilophyllum Morris in Grant, 1840, Williamsonia Carruthers, 1870 emend. Harris, 1969, Weltrichia Braun, 1847 emend. Harris, 1969, Taeniopteris Brongniart, 1828, Czekanowskia Heer, 1876 emend. Harris et al., 1974, Brachyphyllum Brongniart, 1828, Elatocladus Halle, 1913 emend. Harris, 1979 e Carpolithes Brongniart, 1822. Anche i generi Ptilozamites Nathorst, 1878 emend. Antevs, 1914, Nilssonia Brongniart, 1825, Pterophyllum Brongniart, 1828 e Geinitzia Endlicher, 1847 possono essere dubitativamente segnalati per questa flora. Un numero consistente di generi segnalati per il Giurassico della Sardegna sono noti sia nella flora giurassica dello Yorkshire (Inghilterra) sia nelle altre flore giurassiche del territorio italiano, come ad esempio presso la località di Rotzo, in Veneto.

A palaeoenvironmental reconstruction of the Middle Jurassic of Sardinia (Italy) based on integrated palaeobotanical, palynological and lithofacies data assessment

During the Jurassic, Sardinia was close to continental Europe. Emerged lands started from a single island forming in time a progressively sinking archipelago. This complex palaeogeographic situation gave origin to a diverse landscape with a variety of habitats. Collection- and literature-based palaeobotanical, palynological and lithofacies studies were carried out on the Genna Selole Formation for palaeoenvironmental interpretations. They evidence a generally warm and humid climate, affected occasionally by drier periods. Several distinct ecosystems can be discerned in this climate, including alluvial fans with braided streams (Laconi-Gadoni lithofacies), paralic swamps and coasts (Nurri-Escalaplano lithofacies), and lagoons and shallow marine environments (Ussassai-Perdasdefogu lithofacies). The non-marine environments were covered by extensive lowland and a reduced coastal and tidally influenced environment. Both the river and the upland/hinterland environments are of limited impact for the reconstruction. The difference between the composition of the palynological and palaeobotanical associations evidence the discrepancies obtained using only one of those proxies. The macroremains reflect the local palaeoenvironments better, although subjected to a transport bias (e.g. missing upland elements and delicate organs), whereas the palynomorphs permit to reconstruct the regional palaeoclimate. Considering that the flora of Sardinia is the southernmost of all Middle Jurassic European floras, this multidisciplinary study increases our understanding of the terrestrial environments during that period of time.

New insights into the Middle Jurassic floras of Sardinia (Italy) - The Miccolis Collection at the Museo di Storia Naturale of Venice, Italy

The fossil plants of the Domenico Miccolis Collection, stored at the Museo di Storia Naturale of Venice (Italy), are from the Middle Jurassic Genna Selole Formation of central Sardinia. The assemblage contains 11 taxa: Marattia intermedia, Phlebopteris muensteri, P. braunii, Coniopteris sp. cf. C. hymenophylloides, Dicksonia kendallii, Eboracia sp. cf. E. lobifolia, Cladophlebis sp., Weltrichia sp. cf. W. whitbiensis, Geinitzia divaricata, Brachyphyllum expansum and Carpolithes sp. 2. Six species are described for the first time from the Jurassic strata of Sardinia (and Italy), thus increasing the known biodiversity of the flora of this age from these regions. The newly identified taxa have several characters in common with the well-studied Yorkshire flora (UK) indicating strong floristic affinities between southern and western Europe during the Jurassic.

Mineralogical, petrographic, and physical investigations on fossiliferous middle Jurassic sandstones from central Sardinia (Italy) to define their alteration and experimental consolidation

In the present work, the mineralogical-petrographic and physical features of Middle Jurassic sandstones with macrofossil plant remains belonging to the Domenico Lovisato collection, housed at the Geological and Palaeontological Museum of the Cagliari University (Sardinia, Italy), have been studied to define the alteration processes and the consolidating treatment. These sandstones, coming from the Genna Selole formation (central Sardinia), show evident problems of physical decay, due to petrophysical and compositional characteristics such as high porosity, low cementing degree, and presence of clay minerals (e.g., phyllosilicates). This latter leads to subsequent cyclic mechanisms of hydration/dehydration, which affect these sedimentary rocks. For this purpose, five main different sandstone specimens with evident crystalline matrix decohesion have been selected and analyzed. To define their mineralogical-petrographic (composition, microstructure) and physical characteristics (real and bulk densities, helium porosity, water absorption, mechanical strength, etc.), the optical microscope (OM) in polarized light, X-ray powder diffraction analysis (XRPD), helium and water pycnometer, and point load test were used. Testing the most suitable and compatible products for consolidation and time-saving of the palaeobotanical remains, several experimental treatment tests have been performed using four chemical products (i.e., alkoxysilane ethyl silicates and Na/K-silicate).

Past environments of Sardinian archaeological sites (Italy, West Mediterranean Sea), based on palynofacies characterization

Abstract A study method based on characterization of palynofacies (organic matter, palynomorphs) preserved in sediments was applied to obtain information about past environments of Sardinian sites. Organic matter (OM) was classified in ten categories according to its biological source, ecological characteristics, morphology and preservation state. These categories included woody and non-woody particles (cuticles, amorphous organic matter), phytoclasts, spores and pollen grains, gelified particles, and altered phytoclasts that ranged from transparent to opaque fragments. Cluster analysis classified the samples into associations. Each cluster includes stations with a similar spatial distribution pattern. The characterization of the different types of OM was coupled with palyno-logical analyses to produce suggested hypotheses about past vegetation, human activity and land use in Sardinia.

Middle Pennsylvanian vegetation of the San Giorgio Basin, southern Sardinia (Italy)

The small, intramontane San Giorgio Basin in southwestern Sardinia has yielded plant macrofossils dominated by sphenophytes, but with subsidiary pteridosperms, ferns, (?)noeggerathians and cordaitanthaleans. They belong to the upper part of the Crenulopteris acadica Zone or possibly the Odontopteris cantabrica Zone, indicating a late Asturian or Cantabrian (≡ late Moscovian) age. They therefore correlate with the post-Leonian deposits in northern Spain, the Nýřany Member in Western and Central Bohemia, and the Llantwit Beds in South Wales. The presence of post-tectonic deposits of this age is further evidence of the widespread influence of the Leonian Phase of tectonic activity in middle Asturian times, whose effect can be observed across Europe. The San Giorgio Basin is therefore a late Variscan rather than post-Variscan basin.