Dispersal pathways in the early Messinian Adriatic foreland and provenance of the Laga Formation (Central Apennines, Italy)


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Dispersal pathways in the early Messinian Adriatic foreland and provenance of the Laga Formation (Central Apennines, Italy)
Sedimentary Geology
Stalder Nadja Franziska, Fellin Maria Giuditta, Caracciolo Luca, Guillong Marcel, Winkler Wilfried, Milli Salvatore, Moscatelli Massimiliano, Critelli Salvatore
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The early Messinian Laga Formation represents a turbidite complex deposited in the Late Neogene foreland basin
system of the growing Apenninic chain. While the stratigraphy and physiography of the Laga Basin are well
known, the source of its sediments is contentiously claimed to be either recycled Apenninic or primary Alpine.
Furthermore, a shift in paleocurrentwas proposed as a marker of provenance change around 6Ma. By combining
double-dating of detrital zircons (fission-track and U-Pb dating) with compositional analyses, the sedimentary
provenance of the lower Laga arenites and differences between the proximal channelized and distal lobe facies
are addressed. Due to sediment sorting processes, the lobe facies shows a reduced heavy mineral spectrum relative
to the channelized facies. Hence, proximal deposits reflect their hinterland lithologies better than their distal
counterpart and should be preferred in provenance analyses. The petrographic composition of the Laga units implies
amajormetamorphic source combinedwith an additional dolomite and carbonate source.No compositional
difference spanning the shift in paleocurrents is observed,which therefore likely reflects the evolving topography
of the foreland due to syn-sedimentary tectonics. Detrital zircon fission-track data reveal youngest age populations
at ~16–17 Ma and lag times in the range of 9 to 11Ma that can be related to modern fission-track ages observed
in the Central Alps. The two major 238U/206Pb age populations, centered at 277.5 and 37.5 Ma, represent
(post-)Variscan events and the Paleogene magmatic activity in the Central Alps, specifically the Adamello complex.
The Central and Southern Alps are thus inferred as the major source for the early Messinian Laga arenites.
The pathways of the sediments from the Alps to the Laga Basin crossed the Alps-Apennines foreland and passed
on the outer Apenninic wedge-top along elongated and tectonically controlled basins and channels that entered
the basin from the north and northwest. The transfer could have been direct along the Apenninic depozones.
Additionally, late Tortonian sediments fromthe Alps could have been temporarily stored on top of the Apenninic
wedge, e.g. in the Marnoso-arenacea Basin, and then seamlessly cannibalized into the Laga Basin.
Provenance Analysis, Apennines, U-Pb dating, Palinspastic reconstruction
Create date
23/10/2017 11:28
Last modification date
21/01/2020 15:53
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