Pierluigi Pieruccini

A late Lower Pliocene planation surface across the Italian Peninsula: a key tool in neotectonic studies

Abstract An integrated geological–geomorphological approach is proposed in order to provide more information for the assessment of neotectonic deformation in the Apennines. On this basis, it can be stated that: (1) a major flat planation surface is recognisable across the whole Italian Peninsula; (2) it is better preserved on harder rocks and in the higher parts of the local relief; (3) it cuts strata ranging in age from Palaeozoic to early Lower Pliocene; (4) it smoothed tectonic structures older than early Lower Pliocene; (5) it is buried below continental and marine deposits younger than late Lower Pliocene; (6) it is displaced and deformed by local thrust re-activation and, since the Lower Pleistocene, by high angle normal faults. Displacement analysis of this morphological feature at local scale allowed us to discriminate between pre- and post-planation tectonic deformations, hence providing useful information about the rates of uplift and faulting in the Apennines.

The Geomorphological Map of Mt. Amba Aradam Southern Slope (Tigray, Ethiopia)

Abstract Please click here to download the map associated with this article. The geomorphological map described below covers an area of about 100 km, located on the southeastern slope of Mt. Amba Aradam (northern Ethiopia). It has been produced within the Ethio-Italian Cooperation Programme, in order to understand the recent evolution and present-day trends of the area as a basic tool for land reclamation/rehabilitation projects. The survey was carried out in three successive work campaigns (February 1995, February-March 1996 and December 2002) following the Italian Environmental Agency guidelines. The main geomorphological processes responsible for present-day landscape modelling in the investigation area, are gravity-driven mass movements and slope erosion due to running water. They strongly affect human activities, especially in terms of agriculture and infrastructure management. This map may therefore represent a useful document for land management as well as the initial step for the assessment of geomorphological hazard and risk.

A new vertebrate fossiliferous site from the Late Quaternary at San José on the north coast of Ecuador: preliminary note

A new fossiliferous site is described south of Manta on the north coast of Ecuador. Estuarine sediments overlying Quaternary terraced deposits contain abundant vertebrate remains belonging to the following taxa: Eremotherium cf. laurillardi or E. rusconii, Haplomastodon chimborazi, and Geochelone s.l. On the basis of geological context and the fossil assemblage, a probable Early Holocene age is suggested, although a latest Pleistocene age cannot be ruled out. This discovery will provide crucial new information to enhance knowledge of the geologic and faunistic evolution of the area.

Seismic characterization and reconstruction of reference ground motion at accelerometric sites of the Italian national accelerometric network (RAN)

We present a field procedure that has been extensively used in Italy to characterize local seismic response at accelerometric sites and to retrieve ground motion at reference soil conditions by deconvolution analysis. To allow a generalized application to large areas where borehole data are generally lacking or inadequate for the seismic characterization for soils down to the reference seismic bedrock, cost-effectiveness of the considered procedures is a main issue. Thus, major efforts have been devoted to optimize available information and exploit fast and cheap surface geophysical prospecting. In particular, geological/geomorphological survey and passive seismic prospecting (both in single- and multi-station configurations) were jointly considered to reconstruct seismo-stratigraphical site conditions. This information was then used to feed numerical modeling aiming at computing the local seismic response and performing a deconvolution analysis to reconstruct ground motion at reference soil conditions. Major attention was devoted to evaluate and manage uncertainty involved in the procedure and to quantify its effect on final outcomes. An application of this procedure to a set of sites included in the Italian Accelerometric Network is presented.

Geomorphological map and land units at 1:200,000 scale of the Siena Province (Southern Tuscany, Italy)

Abstract Please click here to download the map associated with this article. Small scale geomorphological maps and land unit classification of large areas are not common due to the high degree of generalisation required to represent landforms originally mapped at larger scale (i.e. 1:10,000). Here we present a 1:200,000 scale geomorphological map of the Siena Province (Tuscany, Italy) where the landforms related to different processes have been synthesised into a map representing the main landscape units. The process of generalisation follows the overlapping of the main processes and landforms grouped in 6 main categories: geology, land use, slope, structural/selective erosion, gravity and running water. The final map indicates the presence of seven main homogeneous landscapes characterised by typical associations of landforms and processes. The reference scale allows the analysis of the entire Siena Province and may be used for landscape evaluation, including natural hazards and related susceptibility.

Planation Surfaces and the Long-term Geomorphological Evolution of Ethiopia

Four major planation surfaces (PS) characterize the Ethiopian geology and landscape. They were modelled near or at sea level before the Ordovician (PS1), before the Late Triassic (PS2), before the Cenomanian (PS3), and before the Oligocene (PS4). These are unconformities in the sedimentary sequence recognizable across the entire country and the surrounding regions that due to uplift can be locally exhumed to generate wide steps in the landscape. At the top of the sequence, that also corresponds to the higher parts of the highlands, the flat depositional surface of the continental flood basalts (CFB) is preserved over large areas. However, a series of deep large palaeovalleys dissecting the CFB have been recognized on the water divides of the Afar, the Main Ethiopian Rift (MER), the Southern Ethiopian Rift (SER), and the Somalian and Sudan lowlands that are the main geomorphological features of the country. The palaeovalleys testify to a radial pattern that originated from the dome created by the emplacement of the CFB. They are easily recognizable to the south of Dire Dawa and in the northern part of the country. They were modelled over the pre-volcanic bedrock but in most of the highlands were buried under later volcanic products. The deep erosion of the dome and the later volcanic filling can explain the results of the previous thermochronological investigation. Unfortunately, the thickness of the CFB could have led to the reset of the apatite fission tracks (AFT) during the Oligocene and it is difficult to separate the effects of deep erosion from that of uplift, also considering that they can be closely related. In any case, a progressive incision of the thicker part of the dome is documented soon after the CFB deposition in the Blue Nile Gorge and during the Miocene and the Plio-Pleistocene in many other parts of the country.

Tuscany Hills and Valleys: Uplift, Exhumation, Valley Downcutting and Relict Landforms

The Tuscany physical landscape is the result of processes of selective erosion initiated by regional uplift. The overall geomorphological setting is characterized by “highlands” or mountain ridges alternated with “lowlands” or basins filled with Mio-Pliocene continental and marine sediments. A planation surface was shaped over bedrock, including Pliocene marine terrains, and is widely preserved on top of the mountain ridges. As a result of uplift, the sedimentary infillings of the Pliocene synform basins were affected by river incision. Gully and badland erosion dominate the clayey terrains while cuestas, mesas and stepped slopes are found in sandstones and conglomerate terrains. Large karstic depressions are also found. In the past, these hosted palaeo-springs that alimented travertine and calcareous tufa deposition which spread out to occupy large valley sectors.

Seismic hazard assessment at municipality scale: the Unesco Cultural Heritage site of San Gimignano (Italy)

AbstractIn the frame of the project Rischio Sismico negli Edifici Monumentali-RiSEM (Seismic Risk in Monumental Buildings), a seismogeological reference model was developed for the historical cente...