Luca Trombino

The palaeoclimatic significance of paleosols in Southern Fezzan (Libyan Sahara): morphological and micromorphological aspects

Abstract Two chronosequences of deep red soils, located in Southern Fezzan, are described micromorphologically. The oldest member is probably Late Tertiary in age and has lateritoid characteristics. The intermediate member, of Middle Pleistocene age, displays moderate rubification and much illuvial clay. The most recent member, of Early Holocene age, has weak rubification and very little illuvial clay. The chronosequences of paleosols can be explained by pedogenesis in a humid pedoclimate on stable surfaces during the Quaternary.

The loess-paleosol sequence at Monte Netto: a record of climate change in the Upper Pleistocene of the central Po Plain, northern Italy

PurposeAt the northern fringe of the Po Plain (northern Italy), several isolated hills exist, corresponding to the top of Late Quaternary anticlines. These hills were thoroughly surveyed for their soils and surficial geology, furnishing detailed archives of the palaeoenvironmental evolution of the area. A new, thick and complex loess-paleosol sequence, resting upon fluvial/fluvioglacial deposits, exposed in a quarry at the top of the Monte Netto hill was studied in detail to elucidate its significance.Materials and methodsHighly deformed fluvial and fluvioglacial deposits, probably of Middle Pleistocene age, are exposed in a clay pit at Monte Netto, underneath a 2- to 4-m-thick loess-paleosol sequence. A geopedological, sedimentological and micropedological investigation of the sequence shows a distinctive difference between the B horizons forming the sequence, while luminescence and radiocarbon age determinations and the occurrence of Palaeolithic lithic assemblages elucidate the chronology of the sequence.Results and discussionThe pedosedimentary sequence consists of several loess layers showing different degrees of alteration; loess deposition and weathering occurred, according to optically stimulated luminescence (OSL) and AMS-14C dating as well as archaeological materials, during the Upper Pleistocene. The lower part of the section consists of strongly weathered colluvial sediments overlying fluvial and fluvioglacial sediments. A tentative model of the exposed profiles involves the burial of the anticline, which forms the core of the hill, by loess strata since Marine Isotopic Stage (MIS) 4 and their subsequent weathering (and truncation) during subsequent interstadials. The degree of weathering of buried B horizons increases from the top of the sequence toward the bottom, suggesting a progressive decrease in the intensity of pedogenesis. Finally, the highly rubified paleosol at the top of the hill is regarded as a buried polygenetic soil or a vetusol, developed near the surface since the Middle Pleistocene.ConclusionsThe palaeopedological, geochronological and geoarchaeological analyses permit to define the phases and steps of development of the Monte Netto pedosedimentary sequence; the lower part of the sequence is dated to the Mid-Pleistocene, whereas loess accumulation occurred between MIS 4 and MIS 2. Moreover, analyses help to clarify the climatic and environmental context of alternating glacial and interstadial phases, during which the sediments where deposited, deformed and weathered.

Progressive offset and surface deformation along a seismogenic blind thrust in the Po Plain foredeep (Southern Alps, Northern Italy)

Here we present, for the first time in the Po Plain foredeep (Northern Italy), the middle to late Pleistocene growth history of an outcropping secondary fold and related faults, whose progressive deformation over an intermediate time window (105 years) is driven by an underlying seismogenic blind thrust. We trenched and logged an outcropping decametric secondary anticline, related to a deeper blind compressional structure, which deforms fluvial sediments and an overlying loess-paleosol sequence. Folded units were dated, using radiocarbon and optically stimulated luminescence methods, to the late Pleistocene–Holocene and tentatively correlated with glacial-interglacial phases occurring during the time interval from marine isotope stage 6 to the present. A multistep retrodeformation of the fold allowed us to calculate uplift rates for this secondary and shallow anticline, varying between 0.02 and 0.1 mm/yr since circa 200 kyr. Trishear forward deformation modeling of the fold indicates that the amplification of the observed fold could be caused by two shallow thrusts formed through a break-backward activation. This generated a decametric surface fold whose most recent growth was associated with bending-moment normal faulting in the crestal and forelimb region. Our observations demonstrate that near-surface compressive tectonics can be caused by blind thrusting, via a complex array of fault and folds: upward strain propagation and generation of shallow low-angle thrust and related folding seem to be mainly due to secondary fold-related faulting, according to an out-of-syncline thrusting mechanism.

The nest of the mud-dauber wasp, Sceliphron spirifex (Hymenoptera, Sphecidae): application of geological methods to structure and brood cell contents analysis

Abstract A collection of nests of Sceliphron spirifex from nine farms in Lombardy (Italy) enabled us to study their structure using a new approach involving some geological methods, and to add information regarding brood cell contents. Granulometric analysis revealed that the size of the particles used to build the nest does not depend on geographical location. The low amount of organic matter in the nest building material is inconsistent with the use of saliva, in contrast to a previous hypothesis. We identified micro‐morphological homogenous zones in cell walls that represent the different sites where soil was collected by the wasps, which appear to be 3–4 for every nest. The method employed allowed us to confirm that the cells are built in a concentric way around the lumen. The prey content of each cell consisted of 6–14 spiders, belonging to four families; the largest number of prey species and the most abundant genera, Larinioides Caporiacco and Araneus Clerck, belong to Araneidae. Most prey were young individuals. The rate of parasitism, due to Díptera and Ichneumonidae, was generally high.

Petroplinthite formation in a pedosedimentary sequence along a northern Mediterranean coast: from micromorphology to landscape evolution

PurposeThe petroplinthic horizon is a layer of indurated material in which Fe is an important cement, and it pertains to the pedogenetic material called “laterite”. The aim of this paper is to document the evolution of a coastal pedosedimentary sequence that developed in NW Italy during the Quaternary and discuss the genesis of its petroplinthic horizon within the context of environmental changes that should not have been favourable to lateritisation processes.Materials and methodsThe palaeosol profile was described, and the soil horizons were grouped into pedostratigraphic levels. The horizons were characterised using laboratory routine analysis, X-ray diffraction and thin section micromorphology. In addition, a scanning electron microscope examination of the back-scattered images and an elemental analysis were performed on the petroplinthic horizon only.Results and discussionThe micromorphological evidence and mineralogical analyses suggest a polygenetic origin for the profile that reflects the influence of separate processes acting on distinct parent material under different environmental conditions.ConclusionsThe petroplinthic horizon results from a pedogenetic process that occurs during seasonal fluctuations of the water table, whereas the plinthite has no pedogenetic link with the weathered bedrock. The plinthitisation/ferrugunisation derived from iron enrichment and accumulation from an external upslope source and/or by post-depositional precipitation of “secondary” iron phyllosilicates (e.g. hisingerite) is a result of the dissolution of pre-existing hematite in inherited detrital laterite fragments.

Holocene environmental history at the treeline in the Northern Apennines, Italy: A micromorphological approach

The aim of this work is to investigate paleoenvironment at treeline quotas through the help of soil micromorphology. It also assesses how the micromorphological approach can provide information in paleoenvironmental studies where paleosols are available as proxy archives. Nine soil profiles are described across the treeline, between 1723 and 1860 m, on Mt Cusna slope (2121 m a.s.l., Northern Apennines, Italy). Undisturbed samples from selected soil horizons are collected in Kubiëna boxes. From field observations, all the profiles appear to be composed of two main pedogenetic units: the upper one, composed of a recent soil of colluvial origin, and the deeper one, consisting of an underlying more developed buried paleosol. Thin sections give detailed information about the nature and the origin of both pedological units. Four principal phases of paleosol development are detected. A first period of temperate climate with forest cover and contrasted seasons is followed by a phase of change and then by a successive decrease of forest cover. In a last phase, the soil experiences frost action under the effect of a colder climate. The final deposition of colluvium seems to be very recent (historical time). Moreover, multiple colluvial layers are identified. Colluvial material of different origins could be identified as part of dismantled soils similar to the preexisting paleosol. In conclusion, with the help of soil micromorphology, it is possible to assess the existence of past stable forest at least 100 m above the present treeline. The micromorphological approach represents a powerful tool in multidisciplinary paleoenvironmental studies due to its high level of resolution in outlining the individual and successive phases of soil evolution.

Micromorphological and ultramicroscopic aspects of buried remains: Time-dependent markers of decomposition and permanence in soil in experimental burial.

A buried body not only determines an environmental response at the deposition site but it is also affected by the soil. The experiment was performed using eleven swine carcasses buried in an open site (Northern Italy). Changes occurring in bone tissue at different post-burial intervals were evaluated observing thin sections of bones through micromorphological and ultramicroscopic (SEM-EDS) techniques. These methods allowed the identification of: (a) magnesium phosphate (Mg3(PO4)2) crystallizations, probably linked to decomposition of bones and soft tissues; (b) significant sulphur levels which seem to be related to hydrogen sulphide (H2S) fixation in bone tissue; (c) metal oxide concentrations in the form of unusual violet-blue colorations, which probably are evidence of the soils action and penetration in bones, also testified by (d) the presence of mineral grains enclosed in the osseous tissue. The results underline the possibility of identifying both time-dependent markers of decomposition and indicators of permanence in soil in buried bones.

Geomorphology of the Mt. Cusna Ridge (Northern Apennines, Italy): evolution of a Holocene landscape

ABSTRACT The Mt. Cusna ridge, located in the Northern Apennines (North Italy), is a mountain area of relevant geological interest for the interaction through time of distinct geomorphic processes, acting since the end of the Last Glacial Maximum. A geomorphological map at the 1:10,000 scale was produced to characterise the main landforms and processes identifiable on the ridge. From this, a detailed reconstruction of the Holocene landscape history of the area is drawn. After deglaciation, at the end of the Pleistocene, glacial and periglacial processes left wide deposits and barren surfaces. Slope and running water processes acted cyclically on the landscape through phases of stronger slope denudation and landslide activation followed by stability periods. These processes are related to the main climatic changes recorded for the N Apennines during the Holocene. Since the Late Holocene, the impact of human communities may have played a prominent role as an agent of landscape modification.