Publication Date:
2019-04-01
Description:
Rapid and permanent granulometric changes within the clastic sedimentary deposits of the Tiber River are
directly linked to changes in sediment transport capacity and give insight on climate fluctuations and related
sea-level oscillations during Late Pleistocene–Holocene times. In this work, we investigate the stratigraphic
features of the sedimentary fill of the Tiber River channel as far as 30 km from the coast, and of one tributary,
the Grottaperfetta stream. Through direct observation and core sampling of ten, 30 to 80 m deep boreholes,
and the analysis of a large number of stratigraphic log data, we reconstruct a series of transverse sections and
correlate them along a longitudinal profile of the Tiber River course. We provide geochronologic constraints
to the deposition of distinct lithostratigraphic units by means of 8 newly acquired 14C ages and 21 previously
reported ages of intercalated peat layers and wood fragments. Moreover, we review and select 28 radiocarbon
ages fromliterature on the deposits of the Tiber River in the coastal plain, in order to reconstruct the aggradational
history throughout the distal portion of the basin. Finally, we provide curves of sediment aggradation vs. time
during the last 19,000 yr for the different investigated portions of the Tiber River course. We compare them to
sea-level curves from the literature. To perform this comparison, we use a rigorous geotechnical approach to estimate
the subsidence due to sediment compaction, andwe apply a correction to the Present-day elevation of the
dated samples of organic material interbedded with the sedimentary deposits. Two significant sedimentary events at around 13,800 yr BP and 7500 yr BP, marked by sharp stratigraphic and
granulometric changes, are recognized and correlate to important variations in the rate of sea-level rise. Moreover,
we show evidence of an erosional event coupled to a reversal of the granulometry (increase in gain size
of sediments) affecting the whole investigated tract of the Tiber River channel between 5500 and 3500 yr BP
and discuss its possible causes. In particular, we discuss whether besides the change in capacity of transport
due to a climatic change, also a drop in sea level, in the order of 2–3 meters, may have occurred in this time
span, either in response to an increase in global ice volume, glacial isostatic adjustment, or local tectonic uplift.
Description:
Published
Description:
157–176
Description:
4A. Oceanografia e clima
Description:
JCR Journal
Keywords:
Tiber River
;
Holocene climate
;
Fluvio-deltaic sedimentation
;
Post-glacial sea-level rise
;
04.04. Geology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
