Landscape response to tectonic and climatic forcing in the foredeep of the southern Apennines,Italy: insights from Quaternary stratigraphy,quantitative geomorphic analysis,and denudation rate proxies

We present new data about the morphological and stratigraphic evolution and the rates of fluvial denudation of the Tavoliere di Puglia plain, a low‐relief landscape representing the northernmost sector of the Pliocene‐Pleistocene foredeep of the southern Apennines. The study area is located between the easternmost part of the southern Apennine chain and the Gargano promontory and it is characterized by several orders of terraced fluvial deposits, disconformably overlying lower Pleistocene marine clay and organized in a staircase geometry, which recorded the emersion and the long‐term incision history of this sector since mid‐Pleistocene times. We used the spatial and altimetric distribution of several orders of middle to late Pleistocene fluvial terraces in order to perform paleotopographic reconstruction and GIS‐aided eroded volumes estimates. Then, we estimated denudation rates on the basis of the terraces chronostratigraphy, supported by published OSL and AAR dating. Middle to upper Pleistocene denudation rates estimated by means of such an approach are slightly lower than 0.1 mm yr^‐1, in good agreement with short‐term data from direct and indirect evaluation of suspended sediment yield. The analysis of longitudinal river profiles using the stream power erosion model provided additional information on the incision rates of the studied area. Middle to late Quaternary uplift rates (about 0.15 mm yr^‐1), calculated on the basis of the elevation above sea level of marine deposits outcropping in the easternmost sector of the study area, are quite similar to the erosion rates average value, thus suggesting a steady‐state fluvial incision. The approach adopted in this work has demonstrated that erosion rates traditionally obtained by quantitative geomorphic analysis and k_sn estimations can be successfully integrated to quantify rates of tectonic or geomorphological processes of a landscape approaching steady‐state equilibrium. Copyright © 2014 John Wiley & Sons, Ltd.     

Cyclic facies architecture as a key to depositional controls in a distal foredeep: Campanian Mesaverde Group,Wyoming, USA

The Mesaverde Group consists of a thick wedge of fluvial, littoral-deltaic and shallow marine clastics shed into the Cretaceous Western Interior Seaway of North America. The western parts of the seaway lay within the strongly subsiding foredeep of the active Sevier fold and thrust belt further to the west. The study area is located east of the axis of maximum subsidence and is thus in a favourable position to record competing effects of eustasy, sediment supply and thrust-load induced subsidence. Facies and sequence analysis carried out on high quality outcrop and well log data led to the recognition of a complex depositional cycle hierarchy within the typical storm- and wave-dominated inner shelf/shoreface/strand plain and delta systems of the Mesaverde. Fourth-order parasequences and parasequence bundles of estimated 100–400 ka duration are the best recognizable, ubiquitous and most useful stratigraphic units. Their arrangement with respect to sequence boundaries, however, varies with their overall stratigraphic position and also differs from the Exxon models. Mesaverde progradation was interrupted by a major transgression that occurred out of phase with the aggradational to progradational stacking trend of third-order sequences. A proposed genetic model relates large-scale (second-order) sequence architecture to tectonics: a Sevier thrust event as well as Laramide uplift within the foredeep controlled non-linear changes in the accommodation/supply ratio. Parasequence stacking patterns and sequence boundary formation, in contrast, were the product of (global?) eustasy enhanced by short-term, perhaps local, changes in the rates of subsidence and detrital influx.     

The Alpine evolution of the Southern Alps around the Giudicarie faults: A Late Cretaceous to Early Eocene transfer zone

Data supporting relevant Late Cretaceous–Early Eocene sinistral displacement along the Giudicarie fault zone and a minor Neogene dextral displacement along the Periadriatic lineament are discussed. The pre-Adamello structural belt is present only in the internal Lombardy zone, located W of the Adamello massif. This belt is unknown in the Dolomites and surrounding areas located to the E of the Giudicarie lineament. Upper Cretaceous–Early Eocene thick syntectonic Flysch deposits of Lombardy and Giudicarie are well preserved along the southern and eastern border of the pre-Adamello belt (S-vergent Alpine orogen). Towards the E, in the Dolomites and in the Carnic Alps and external Dinarides, only incomplete remnants of Flysch deposits, Aptian–Albian and Turonian–Maastrichtian in age, are present. They can be considered as equivalent to those of Lombardy and Giudicarie formerly in connection to each other along the N-Giudicarie corridor. To the S, the syntectonic Flysch deposits are laterally replaced by the calcareous red pelagites of the Scaglia Rossa and by the carbonate shelf deposits of the Friuli (to the E) and Bagnolo (to the S) carbonate platforms. The different location in the southern structural accretion of the eastern and western opposite blocks (the Dolomites versus the pre-Adamello belt) can be related to the Cretaceous–Eocene convergence. In this frame, the N-Giudicarie fault has been considered as part of a former transfer zone, which produced the sinistral lateral displacement of the Southern Alps front for an amount of some 50 km. During the Late Eocene to Early Oligocene the transfer zone was mostly sealed by the Paleogene Adamello batholith. Oligocene to Neogene compressional evolution inverted the N-Giudicarie fault into a backthrust of the Austroalpine units over the South-Alpine chain.     

Early exhumation of the collisional orogen and concurrent infill of foredeep basins in the Miocene Eurasian–Okhotsk Plate boundary, central Hokkaido, Japan: Inferences from K–Ar dating of granitoid clasts

Abstract   Thick Middle (–Upper) Miocene turbiditic deposits filled very deep and narrow foredeep basins formed in the western margin of the Hidaka collision zone in central Hokkaido. Cobble- to boulder-sized clasts of eight monzogranites and a single granodiorite in the Kawabata Formation in the Yubari Mountains area yielded biotite K–Ar ages of 44.4 ± 1.0 to 45.4 ± 1.0 Ma and 42.8 ± 1.1 Ma, respectively. Major elemental compositions of the clasts all fall in the field of S-type granite on an NK/A (Na₂O + K₂O/Al₂O₃ in molecule) versus A/CNK (Al₂O₃/CaO + Na₂O + K₂O in molecule) diagram, verifying their peraluminous granite character (aluminium saturation index (ASI): 1.12–1.19). These geochronological and petrographical features indicate that the granitoid clasts in the Kawabata Formation correlate with Eocene granitic plutons in the northeastern Hidaka Belt, specifically the Uttsudake (43 Ma) and Monbetsu (42 Ma) plutons. Foredeep basins are flexural depressions developed at the frontal side of thickened thrust wedges. The results presented here suggest that deposition of the Middle Miocene turbidites was coeval with rapid westward up-thrusting and exhumation of the Hidaka Belt. This early mountain building may have occurred in response to thrusting in the Tertiary fold-and-thrust system of central Hokkaido.     

Foreland-dipping normal faults in the inner edges of syn-orogenic basins: a case from the Central Apennines, Italy

Extensional deformations are common within foredeep basins and generally consist of hinterland-dipping normal faults located at the foredeep–foreland transition zones. Foreland-dipping normal faults at the belt–foredeep boundaries, by contrast, are far less documented and their occurrence is not predicted by simple orogenic load models. New surface data integrated with seismic reflection profiles across the Central Apennines of Italy reveal the occurrence of foreland-dipping normal faults located in the inner edges of foredeep depressions. Extensional deformations are systematically found within sequentially younger Tortonian, Messinian and Early Pliocene foredeep basins, thus suggesting that normal fault development was an intrinsic feature of the evolving belt–foredeep–foreland system and could have influenced the stratal architectures of the host syn-orogenic deposits. Foreland extension is consistent with existing geodynamic models for the Apennines and could represent the effects of lithospheric bending: its recognition and documentation elsewhere could provide significant insights to improve our understanding of syn-orogenic basin dynamics.     

Turbidites facies response to the morphological confinement of a foredeep (Cervarola Sandstones Formation,Miocene, northern Apennines,Italy)

The Cervarola Sandstones Formation, Aquitanian–Burdigalian in age, was deposited in an elongate, north‐west stretched foredeep basin formed in front of the growing northern Apennines orogenic wedge. As other Apennine foredeep deposits, such as the Marnoso‐arenacea Formation, the stratigraphic succession of the Cervarola Sandstones Formation records the progressive closure of the basin due to the propagation of thrust fronts towards the north‐east, i.e. towards the outer and shallower foreland ramp. This process produces a complex foredeep that is characterized by syn‐sedimentary structural highs and depocentres that strongly influence lateral and vertical turbidite facies distribution. This work describes and discusses this influence, providing a high‐resolution physical stratigraphy with ‘bed by bed’ correlations of an interval ca 1000 m thick, parallel and perpendicular to the palaeocurrents and to the main structural alignments, on an area of ca 30 km that covers the proximal portion of the Cervarola basin in the northern Apennines. The main aim is to show, for the first time ever, a detailed facies analysis of the Cervarola Sandstones Formation, based on a series of bed types that have proven fundamental to understand the morphology of the basin. The knowledge of the vertical and lateral distribution of these bed types, such as contained‐reflected and slurry (i.e. hybrid) beds, together with other important sedimentary structures, i.e. cross‐bedded bypass facies and delamination structures, is the basis for better understanding of facies processes, as well as for proposing an evolutionary model of the foredeep in relation to the syn‐sedimentary growth of the main tectonic structures. This makes the Cervarola Sandstones, like the Marnoso‐arenacea Formation, a typical example of foredeep evolution.     

塔里木盆地西北缘克孜布拉克剖面下二叠统砂岩沉积构造背景的初步研究

塔里木盆地西北缘的下二叠统由下部的凝灰岩和上部的碎屑浊积岩组成,后者的地球化学特征明显不同于被动大陆边缘沉积,是前渊复理石建造.南天山洋盆经早二叠世的大规模消减后在晚二叠世大部分闭合,相应地,塔北的二叠-三叠系组成了从前渊复理石深海沉积经海陆交互相沉积发育为前陆磨拉石粗碎屑岩的完整序列.     

The Romagna Apennines,Italy: an eroded duplex

The study of clast composition carried out on the alluvial gravels of the Romagna Apennines of northern Italy has provided evidence for an extensive covering of allochthonous units (Ligurian nappe and Epiligurian succession) above the Miocene foredeep deposits (Marnoso‐Arenacea Formation), which has been subsequently eroded during the Late Miocene–Pleistocene uplift. This result is confirmed by the burial history outlined in the Marnoso‐Arenacea Formation through vitrinite reflectance and apatite fission‐track analyses. The Romagna Apennines represent, therefore, a regional tectonic window where the thrust system that displaced the Marnoso‐Arenacea Formation crops out. The geometric relations between this thrust system and the basal thrust of the Ligurian nappe, exposed at the boundaries of the Romagna Apennines (Sillaro Zone and Val Marecchia klippe), are consistent with a duplex structure. Thus, the Romagna Apennines thrust system is an eroded duplex. The duplex roof‐thrust corresponds to the surface of the synsedimentary overthrust of the Ligurian nappe on the Marnoso‐Arenacea Formation; the floor‐thrust is located in the pelagic pre‐foredeep deposits (Schlier Formation). Copyright © 2001 John Wiley & Sons, Ltd.