Guido Parisi

The Eocene-Oligocene Boundary in the Umbrian Pelagic Sequences, Italy

Publisher Summary Detailed biostratigraphic and paleomagnetic studies on Eocene–Oligocene pelagic sequences from Umbria (Central Italy) revealed that deposition across the Eocene–Oligocene boundary was continuous and undisturbed in that area. This chapter presents the data from eight stratigraphic sequences spanning the interval from the Early to Middle Eocene boundary through the Early Oligocene with specific emphasis on the events at the Eocene–Oligocene boundary. To have a complete biostratigraphic and paleomagnetic record, the Contessa highway section was sampled upwards into the northwestern quarry—that mirrors the Contessa quarry of Lowrie—where the Eocene–Oligocene boundary is undisturbed. Lithologically, the scaglia formation is very monotonous except for the major color changes. Visual correlations among sections are limited to minor changes that are not easily detected. Some of these changes, however, appear to be of larger (not local) significance.

Eocene and early oligocene micropaleontology and paleoenvironments in SE Umbria, Italy

A detailed study, based on calcareous nannofossils and planktonic and benthic Foraminifera, has been carried out on five sections in the “Scaglia” Group of the Umbrian region (Visso and Cascia areas, Central Italy). These sections are characterized by continuous pelagic sedimentation and are constituted mainly of marls, marly limestones and limestones of Early Eocene to Early Oligocene age. Calcareous turbidites, with shallow-water skeletal debris, discharged from the Latium-Abruzzi carbonate platform, are interbedded within the pelagic sequences. The biostratigraphic study, based on calcareous nannofossils and planktonic Foraminifera, confirmed the continuous succession of standard events and revealed some new ones. These results allow us to refine the biostratigraphic resolution, with a very good correlation between calcareous nannofossil and planktonic foraminiferal zonations. The major features and events recognized are: • The Early-Middle Eocene boundary (Zones P9–P10) is characterized by the first occurrence (FO) of hantkeninids, by abundant thick-walled Globigerinatheka (G. senni) and by spinose acarininids. A decrease has been noted in planoconvex morozovellids and an increase of low-spired subbotinids. • The benthic assemblage shows a great variability, with an increase in the Zone P11 of the large Heterolepa and Cibicidoides. This is an event of worldwide significance. • In the calcareous nannofossils, the FO of Nannotetrina sp. was used to define the lower boundary of Zone CP13 instead of N. fulgens, because poor preservation prevented identification at the specific level. • The FO of Reticulofenestra umbilica, marking the lower boundary of Zone CP14, occurs in the upper part of Zone P11. • The Zone P13 was recognized indirectly because of the absence of the index species Orbulinoides beckmanni. The base of the zone is close to the FO of Turborotalia cerroazulensis, and is defined by an increase of Catapsydrax sp. and by the last occurrence (LO) of Acarinina bullbrooki. The top of the zone is defined by an increase of the high-spired subbotinids of the S. corpulenta group and the disappearance of Morozovella spinulosa • The Middle/Late Eocene boundary (Zones P14/P15) is characterized by the extinction of the spinose acarininids and of the smooth-walled Planorotalites. From Zone P13 to Zone P15 there is a replacement in the benthic assemblages. In fact, Pleurostomella, Heterolepa and Anomalinoides capitata characterize these zones, bolivinids become abundant and uvigerinids appear around the P14/P15 boundary. • The Late Eocene is characterized by an increase of subbotinids with abortive chambers and of the Turborotalia cerroazulensis lineage. Hantkeninids and cribohantkeninids are rare, particularly C. inflata. The FO of Istmolithus recurvus has been noted at the base of Zone P16. Within this zone, Globigerinatheka index and Turborotalia cunialensis coexist. The LO of G. index is associated with a strong decrease of representatives of the genus Globigerinatheka. At the same level of the LO of G. index, the coeval extinctions of Discoaster barbadiensis and Discoaster saipanensis are noted. Just above this level, within Zone P17, the LO of T. cerroazulensis lineage (T. cocoaensis and T. cunialensis) has been recognized. The Eocene/Oligocene boundary is defined by planktonic Foraminifera at the extinction level of hantkeninids and cribrohantkeninids, shortly following that of the T. cerroazulensis group.

Stratigraphy and geochemical anomalies of the early Toarcian oxygen-poor interval in the Umbria-Marche Apennines (Italy)

Abstract A multidisciplinary approach is used to demonstrate the occurrence of oxygen-poor sediments in theTenuicostatum Zone (Early Toarcian) within the clayey-marly pelagic sediments of Marne del Monte Serrone Formation (Umbria-Marche basin). This approach involves examination of some geochemical anomalies (trace elements), measurement of Total Organic Carbon and observation of benthic foraminifera and trace fossils. A distinction between “ black shale facies ” (BSF1) and “ black shale-like sediments ” (BSF2) allows better identification of the variable anoxic conditions present within the same basin. A high degree of organic matter preservation and major anoxia extensions occur in the middle-upper part of the Tenuicostatum Zone (Early Toarcian) probably related to maximum flooding-high stand of the global Early Toarcian sea-level rise. Several subenvironments showing pelagic conditions and high primary productivity of planktonic organisms (mainly radiolarians and calcareous nannofossils), have been defined on the basis of organic matter content and positive geochemical anomalies. The diversified physiography of the Umbria-Marche basin, related to synsedimentary tectonic activity and circulation patterns, probably determined different intensities of ventilation conditions on the sea-floor.

Biostratigraphic Correlation Between the Central Subbetic (Spain) and Umbro-Marchean (Italy) Pelagic Sequences at the Eocene/Oligocene Boundary Using Foraminifera.

Abstract The most significant events, which occurred during the time interval spanning from the Late Eocene to the Early Oligocene, are preserved in the continous pelagic sequences of the Subbetic basin (Spain) and Umbro-Marchean basin (Italy). A comparative analysis has been carried out between events common to both areas, based on planktonic and benthic foraminifera. The relationship between Hantkeninidae and other selected taxa were used to identify and correlate the biozones identified in the two areas. We show that below the Eocene/Oligocene boundary several successive extinctions occur in the same order both in Spain and in Italy. Particularly, the Turborotalia cerroazulensis group extinction is slightly prior to the Hantkeninidae and large Pseudohastigerina extinctions, which latter mark the Eocene/Oligocene boundary.

MIDDLE JURASSIC - EARLY CRETACEOUS INTEGRATED BIOSTRATIGRAPHY (AMMONITES, CALCAREOUS NANNOFOSSILS AND CALPIONELLIDS) OF THE CONTRADA DIESI SECTION (SOUTH-WESTERN SICILY, ITALY)

Facies and biostratigraphic analyses of the Contrada Diesi succession, cropping out along the northern slope of Mt. Magaggiaro (Sciacca, SW Sicily), provided new data on the Middle Jurassic-Early Cretaceous pelagic sedimentation in the Saccense domain. The richness in ammonites allowed the identification of Bathonian-Kimmeridgian Biozones and Subzones, while the Tithonian-Valanginian interval was defined mainly by calpionellids and calcareous nannofossils. Facies and microbiofacies analyses of the Jurassic-Cretaceous pelagic sediments of the area, together with ammonite, calpionellid and calcareous nannofossil integrated biostratigraphy, were very effective tools for comparison of biostratigraphic events. Many gaps in sedimentation were recognized, the most important spanning the middle and late Berriasian and part of the early Berriasian. The Contrada Diesi succession provides new litho-biostratigraphic data on the Saccense Domain. It suggests a high degree of internal variability tied to the irregular paleotopography of the carbonate platform substrate (Inici Fm.), derived from Early Jurassic tectonics. Gaps in sedimentation in the Contrada Diesi sections indicate that the environment of the Saccense Domain was characterized by a variable rate of sedimentation and energy changes.

INTEGRATED STRATIGRAPHY (RADIOLARIANS AND CALCAREOUS NANNOFOSSILS) OF THE JURASSIC SILICEOUS SEDIMENTS FROM MONTE KUMETA (WESTERN SICILY, ITALY)

Integrated analyses of Calcareous Nannofossils and Radiolarians were carried out in the Monte Kumeta (Sicily) to better define the age of the siliceous sediments (Membro Radiolaritico Intermedio = MRI), which results to be early-middle Bathonian to early Kimmeridgian. The base of this unit shows variable ages in the different sites along the Kumeta palaeoescarpment. Particularly, the ages of the distal sections range from early-middle Bathonian to early Kimmeridgian, whereas the proximal sections show ages from late Oxfordian to early Kimmeridgian. This fact suggests the presence of heteropy between the Membro Radiolaritico Intermedio and the Rosso Ammonitico Inferiore. Moreover, several gaps occur in the MRI and they are restricted to late Bathonian - early Callovian and to late Oxfordian, testifying the times of major tectonic activity along the palaeoescarpment.