Roberto Tinterri

An introduction to the analysis of ancient turbidite basins from an outcrop perspective

Basin Studies Field Methods and Studies Sandstones and Clastics Sequence Stratigraphy. Turbidite sedimentation of ancient orogenic belts are considered as closely related to that of marginal flood-dominated fluvio-deltaic systems. Many conclusions are new and far from conventional. These notes represent a need for fresh air from the area of outcrop studies.

Occurrence of inter-eruption debris flow and hyperconcentrated flood-flow deposits on Vesuvio volcano, Italy

Abstract In the period between AD 79 and AD 472 eruptions, inter-eruption debris flow and hyperconcentrated-flood-flow deposits were deposited in the Somma-Vesuvio areas. These deposits, forming cliffs at the Torre Bassano and Torre Annunziata, were generated by highly erosive floods, whose erosive capacity was enhanced by acceleration due to the steepness of the volcano slopes. In this type of deposits were distinguished five depositional facies (from A to E) outcropping well at Torre Bassano where they are stacked in three fining-upward (FU) sequences, probably representing three forestepping — backstepping episodes in the emplacement area of gravity flows. These five facies from coarse to fine are interpreted to represent the downcurrent evolution of particular composite sediment gravity flows characterized by horizontal segregation of the main grain-size population. The blocking of these highly concentrated composite parent flows would first produce the deposition of the coarse front part to form facies A and then the overriding of this deposit by the bipartite flow, which constitutes the body of the flow. This flow is composed of a highly concentrated basal inertia carpet responsible for the deposition of facies B, C and D and an upper hyperconcentrated flood flow that forms facies E, through traction plus fallout processes, respectively. Finally, the occurrence of “lahar” type events at Somma-Vesuvio region even at present times is discussed.

The Specchio Unit (Northern Apennines, Italy): An Ancient Mass Transport Complex Originated from Near-Coastal Areas in an Intra-Slope Setting

Within the Eocene-Oligocene syn-orogenic deposits of the Epiligurian succession (Northern Apennines of Italy), a field-based study of the Specchio Unit (lower Rupelian) reveals that this complex is made up of three distinct but amalgamated mass-transport deposits (MTDs), the largest of which reaches a maximum volume of ca. 150 km3. These bodies were deposited inside the complex system of intraslope basin systems, developed atop the submerged Ligurian accretionary prism at the collision with the Adria continental plate. The MTDs originated from catastrophic retrogressive collapses starting from the upper slope and involving progressively shallow-water environments, from distal shelfal pro-delta and delta-front sediments up to proximal coastal fan-delta deposits. These recurrent and close in time, catastrophic slope failures were probably caused by tectonic and climatic triggers, such as the enhanced tectonic activity due to incipient Apenninic continental collision and the onset of harsh climatic conditions, as suggested by oxygen isotopic maxima (e.g., Oi-1a event). Although the wedge toe/foredeep systems are generally considered the principal loci of such, usually located in deep-water settings, here we stress the importance of catastrophic mass transport events also atop the wedge, in shallow-water depositional domains. Mass transport processes also have a fundamental role in reshaping the upper physiographic profile of an evolving accretionary wedge. The correct interpretation of such mass transport processes has also important implications for geohazard forecasting in modern active continental margins, for example in terms of tsunamigenic potential.

The tectonically confined Firenzuola turbidite system (Marnoso-arenacea Formation, northern Apennines, Italy)

The Firenzuola turbidite system formed during an important phase of thrust propagation, involving the upper Serravallian deposits of the Marnoso-arenacea Formation (MAF). During this phase the coeval growth of two major tectonic structures, the M. Castellaccio thrust and the Verghereto high, played a key role, causing a closure of the inner basin and a coeval shift of the depocenter to the outer basin. This work focuses on this phase of fragmentation of the MAF basin; it is based on a new detailed high-resolution stratigraphic framework, which was used to determine the timing of growth of the involved structures and their direct influence on sediment dispersal, as well as on lateral and vertical turbidite facies distribution. The Firenzuola turbidite system stratigraphy is characterized by the occurrence of MTCs (Mass Transport Complexes) and thick sandstone accumulation in the depocentral area, which passes to finer drape over the structural highs; the differentiation between these two zones increases over time and ends with the deposition of marly units over the structural highs and the emplacement of the Visignano MTC. According to the stratigraphic pattern and turbidite facies characteristics, the Firenzuola System (Unit V in the works by Muzzi Magalhaes and Tinterri) has been split into two sub-units, namely Firenzuola I (sub-Unit Va) and Firenzuola II (sub-Unit Vb): the former is quite similar to the underlying deposits (Unit IV), the latter shows the main fragmentation phase, testifying to the progressive isolation of the inner basin and a coeval shift of the depocenter to the outer basin.

Sedimentary facies control on mechanical and fracture stratigraphy in turbidites

Natural fracture networks exert a first-order control on the exploitation of resources such as aquifers, hydrocarbons, and geothermal reservoirs, and on environmental issues like underground gas storage and waste disposal. Fractures and the mechanical stratigraphy of layered sequences have been intensively studied to unravel the relationships between bed thickness and fracture spacing, but less attention has been paid to intrabed fracturing patterns due to the intrinsic local variability of sedimentary processes and products. Among sedimentary rocks, turbidites show great lateral and vertical variability of textural characteristics and depositional facies, which are expected to strongly influence the location and density of fractures. To better understand the contribution of stratigraphic, sedimentologic, and petrophysical properties on fracture patterns, we performed a high-resolution study on a selected stratigraphic interval of jointed foredeep turbidites in the Miocene Marnoso-Arenacea Formation (Northern Apennines, Italy). Cumulative statistical relations of field and laboratory structural, sedimentologic, and petrophysical data significantly improved when analyzed at the sedimentary facies scale. In particular, for facies recording different cross-flow (i.e., longitudinal to the paleocurrents) depositional conditions within the parent turbidity currents, we observed three-dimensional anisotropies of rock hardness (i.e., uniaxial compression) that were positively correlated with normalized fracture intensities, indicating a primary sedimentary control on fracture distribution. This type of intrabed joint distribution has crucial practical implications for the lateral prediction and evaluation of mesoscale fracture patterns in turbidite sequences.

Seismo-stratigraphic Study of the Plio-pleistocene Deposits of the Central Adriatic Sea, Italy

An integrated 3D Seismo-Stratigraphic Study was carried out on a portion of the Central Adriatic Sea (Italy), offshore the coast of the Abruzzo region, aimed to define and understand in detail the Plio-Pleistocene stratigraphic succession, the evolution of this area through this specific geological time, and the implication from and E&P perspective. The study is based on good quality 3D data, wells and regional 2D seismic lines. The stratigraphic succession of the foredeep Plio-Pleistocene deposits presented in this work, shows a general shoaling up trend in which the vertical evolution from deep water deposits into deltaic and nearshore strata is related to the progressive displacement of the main depocentres eastward produced by thrust propagation toward the outer margin of the foredeep basin. In this note, in particular, the Middle/Upper Pliocene and Pleistocene part is described in its main seismo-stratigraphic characteristics. A detailed 3D seismic facies analysis has infact allowed to identify, interpret and understand from a depositional point of view several interesting geological “objects” at different scale: in particular, possibly for the first time in this area, well developed sediment drifts, related to bottom currents and associated to deep water channel complexes, were described.

Control of Thrust Propagation on Turbidite Sedimentation

In foreland basins, the deep and narrow trough which forms adjacent to the thrust front is commonly termed foredeep, and, until the orogenic wedge is not significantly uplifted and emerged, the trough is characteristically filled in with axial turbidites sourced from fluvio-deltaic systems located in emerged areas of adjacent orogens where substantial tectonic uplift has already occurred.

From axial parallel to orthogonal groundwater flow during fold amplification: insights from carbonate concretion development during the growth of the Quattro Castella Anticline, Northern Apennines, Italy

This paper is based on a multidisciplinary field and laboratory study of carbonate concretions developed in poorly lithified Quaternary, syn-kinematic sediments along the Quattro Castella Anticline, Northern Apennines, Italy. The studied concretions consist of both tabular (parallel to bedding) and elongate single to coalescent concretionary bodies oriented at different angles to the bedding throughout the exposed stratigraphic succession. The dimensions of the concretions range from a few centimetres for single elongate concretions up to several metres for tabular to coalescent concretions. Field observations and petrophysical data indicate that the concretions developed preferentially in sediments characterized by mean grain sizes of 90–290 μm and a permeability ranging from 7 × 102 to 7 × 104 mD. Carbon and oxygen stable isotope analyses in conjunction with the petrographic investigations indicate that the precipitation of concretionary calcite occurred in a meteoric vadose realm during early eogenesis and subsequently in a meteoric phreatic environment. Diagenetic data and concretion patterns in syn-tectonic sediments suggest they formed during the lateral propagation of the anticline, which, in turn, promoted a change in the local topographic–hydraulic gradient from fold axial parallel to fold orthogonal. The integrated analysis of carbonate concretions provides a useful tool with which to unravel the palaeo-fluid flow history and therefore to predict fluid circulation patterns in folded siliciclastic rocks. Supplementary material: Complete isotopic data from both hand samples and thin sections, together with statistical analysis, scanning electron microscope cement images and grain size distributions with the standard operative procedure tests performed, and detailed permeability measurements are available at https://doi.org/10.6084/m9.figshare.c.4087019

Facies and Processes of Turbidite Systems

Over the past two decades marine geological investigations, outcrop studies, laboratory experiments and numerical modelling, and, particularly, a wealth of seismic, well-log and core data derived from extensive exploration for hydrocarbons carried out in many offshore basins worldwide, have provided an increasing body of evidente indicating the very complex and stip poorly understood nature of many deep-water sandstone facies.