Terrestrial records of deglaciation events during terminations V and IV in the central Apennines (Italy) and insights on deglacial mechanisms

Abstract

Abstract40Ar/39Ar geochronology constraints to aggradational phases and grain size variations show that the two large gravel beds occurring in the sedimentary filling of the Liri fluvial-lacustrine basin (central Italy) recorded the occurrence of deglaciation events synchronous within uncertainties with global meltwater pulses at ca. 450 and 350 ka. In particular, we find a precise match between the ages of gravel deposition and the occurrence of moderate sea-level rise events which anticipate those more marked during the glacial termination V and IV in the Red Sea relative sea level curve, as already verified by data from the Tiber River catchment basin. Such correspondence suggests that gravel deposition is facilitated by melting of Apennine mountain range glaciers, which provide the water transport energy and a surplus of clastic input to the rivers draining the mountain regions and flowing into the Tyrrhenian Sea. Therefore, the thick gravel beds intercalated in the sedimentary filling of the catchment basins of the major rivers in central Italy may be regarded as an equivalent proxy of large deglaciation events, similar to the ice-rafted debris in northern Atlantic. Consistent with this hypothesis, we also show the close correspondence between the occurrence of particularly mild (warmer) minima of the mean summer insolation at 65° N and these early aggradational phases, as well as with other anomalous early sea-level rises occurring c. 750 ka and 540 ka at the onset of glacial termination VIII and VI, and 40 ka at the onset of the so-called Heinrich events.

Evidence for a Constant Slip Rate Over the Last ∼40 ka Along the Mt. Morrone Fault System in Central Apennines

“…(2009). Specifically, recent studies in the Liri area (southwest of Sulmona) (Marra et al., 2022) observed the occurrence of one of the so‐called Heinrich events (Hemming, 2004) at 40 ka, a mild minimum (warmer) period in MIS3 that produced the last major emplacement of the aggradational phase, that may be related to the alluvial‐slope sedimentation and UTS formation.In this scenario, the tectonic activity was noted from the westernmost faults offsetting the alluvial fans in Roccacasale (F2 in Figure 16c). This agrees with the younger structural evolution observed by Vignaroli et al.…”

“…(2009). Specifically, recent studies in the Liri area (southwest of Sulmona) (Marra et al., 2022) observed the occurrence of one of the so‐called Heinrich events (Hemming, 2004) at 40 ka, a mild minimum (warmer) period in MIS3 that produced the last major emplacement of the aggradational phase, that may be related to the alluvial‐slope sedimentation and UTS formation.…”

“…The large amount of alluvial-fluvial and slope sedimentation of the basin outcropping at the mountain toe, such as the Malepasso alluvial fan (T1 related-deposits), is related to this period, as suggested by Gori et al (2009). Specifically, recent studies in the Liri area (southwest of Sulmona) (Marra et al, 2022) observed the occurrence of one of the so-called Heinrich events (Hemming, 2004) at 40 ka, a mild minimum (warmer) period in MIS3 that produced the last major emplacement of the aggradational phase, that may be related to the alluvialslope sedimentation and UTS formation. In this scenario, the tectonic activity was noted from the westernmost faults offsetting the alluvial fans in Roccacasale (F2 in Figure 16c).…”

Glacier Melting Triggers Massive Gravel Deposition in Central Italy's River Basins, Unveiling Deglacial Events From 1250 to 780 ka

“…One defining characteristic of the aggradational successions of the Paleo-Tiber River is the sudden shift in sedimentary facies between the lower and upper sections of the sedimentary record (Giaccio et al, 2021;Marra et al, 2008Marra et al, , 2013Marra et al, , 2016Marra et al, , 2022. This is also observed in the 120-m-thick succession extracted from the PR1 borehole, where a sharp boundary separates a layer of well-rounded limestone and chert pebbles, with diameters reaching up to approximately 10 cm (as measured by the core's inner diameter), embedded in a matrix of silty sand (0.5-1.0 mm), from a separate layer of mostly clayey <0.004 mm and sandy <0.5 mm sediments that is several meters thick (5-9 m, as shown in Figure 3 and Figures S2 to S8 in Supporting Information S1).…”

“…The coarse clastic sediments found at the base of the aggradational successions of the (paleo-) rivers in central Italy, consisting of gravel with a grain size between >1 and <10 cm, have been identified as evidence of global deglacial events occurred during the Pleistocene (Giaccio et al, 2021;Marra et al, 2022). According to the sedimentary model proposed by Marra et al (2008Marra et al ( , 2016, the transportation of coarse gravel from the Apennine Mountain chain through the (Paleo-) Tiber River channel, and its subsequent accumulation on the Tyrrhenian Sea coast, is only possible during glacial terminations due to several factors that occur simultaneously.…”