Roberta Pini

Onset of major Pleistocene glaciations in the Alps

During maximum Pleistocene glacial expansions, the Alpine ice cap invaded the Central Europe uplands and Italian Southalpine foothills. Periglacial basins, such as the Po River Basin, are natural collectors of sediments that record the past biological and climatic changes that involve the waxing and waning of major ice caps. In a 200-m-long core from the central Po Plain, stratigraphic evidence for one such major glacial pulse of the nearby Alpine ice cap is recorded by a sequence boundary, termed the R surface, associated with a drastic reorganization of vegetational, fluvial, and Alpine drainage patterns. The R surface, seismically traceable across the Po Plain subsurface, was constrained magnetostratigraphically to the first prominent Pleistocene glacio-eustatic lowstand of marine isotope stage (MIS) 22 at 0.87 Ma. MIS 22 corresponds to the end of the Mid-Pleistocene Revolution, a marked reorganization of Northern Hemisphere glaciation pattern that took place in the late early Pleistocene. We suggest that the R surface formed at Mid-Pleistocene Revolution‐MIS 22 time, during the onset of the first major Pleistocene glaciation in the Alps.

Circum-Mediterranean fire activity and climate changes during the mid-Holocene environmental transition (8500-2500 cal. BP)

A mid- to late-Holocene synthesis of fire activity from the Mediterranean basin explores the linkages among fire, climate variability and seasonality through several climatic and ecological transitions. Regional fire histories were created from 36 radiocarbon-dated sedimentary charcoal records, available from the Global Charcoal Database. During the mid-Holocene ‘Thermal Maximum’ around 7500—4500 cal. BP, charcoal records from the northern Mediterranean suggest an increase in fire while records from the southern Mediterranean indicate a decrease associated with wetter-than-present summers. A North—South partition between 40° and 43°N latitude is apparent in the central and western Mediterranean. Relatively abrupt changes in fire activity are observed c. 5500—5000 cal. BP. Records of Holocene fire activity appear sensitive to both orbitally forced climate changes and shorter-lived excursions which may be related to North Atlantic cold events, possibly modulated by an NAO-like climate mechanism. In cases where human—fire interactions have been documented, the regional coherency between fire occurrence and climate forcing suggests a dominant fire—climate relationship during the early—mid Holocene. The human influence on regional fire activity became increasingly important after c. 4000—3000 cal. BP. Results also suggest that: (1) teleconnections between the Mediterranean area and other climatic regions, in particular the North Atlantic and the low latitudes monsoon areas, influenced past fire activity; (2) gradual forcing, such as changes in orbital parameters, may have triggered abrupt shifts in fire activity; (3) regional fire reconstructions contradict former notions of a gradual (mid- to late-Holocene) aridification of the entire region due to climate and/or human activities and the importance of shorter-term events; (4) Mediterranean fire activity appears hightly sensitive to climate dynamics and thus could be considerably impacted by future climate changes.

Evidence for late Alpine tectonics in the Lake Garda area (northern Italy) and seismogenic implications

We investigated the recent evolution of the Po Plain–Alps system by integrating subsurface geophysical data from the Po Plain with new stratigraphic and structural observations from the Southern Alps margin. Inversion of structural data and chronology provided by stratigraphic constraints led to the definition of three tectonic events since the Pliocene, namely, the intra-Zanclean, the Gelasian, and the middle Pleistocene, driven by an axis of maximum compression formerly oriented NE (intra-Zanclean) and then to the NNW (Gelasian and middle Pleistocene). The associated deformation has been accommodated by two sets of faults consisting of NNE-trending thrust faults, mostly represented in the western sector of Lake Garda, and NW-trending strike-slip faults, observed in the southern and eastern sectors. The interplay between these two sets of faults is interpreted to produce short ( w w > 6.5) along the NW-trending strike-slip faults. In this framework, the newly defined Nogara fault and the Sant’Ambrogio fault, all pertaining to the NW-trending system, are regarded as potential candidates for the seismogenic source of the January A.D. 1117 event, the most destructive earthquake in the Po Plain.