Abstract
Through a geomorphological study relying on statistically assessed classes of hilltop elevations, we reconstruct a suite of paleo-surfaces along the Tiber River Valley north of Rome that we identify as fluvial terraces formed by interplay between global sea-level fluctuations and regional upift. Using biostratigraphic constraints provided by marine through continental deposits of Santernian age, we recognize the oldest terrace in this area, corresponding to an early coastal plain of late Santernian-Emilian age. By assuming the simple chronological principle of a staircase geometry we correlate the sea-level highstands of MIS 21 through MIS 5 with the lowest eight paleo-surfaces. By plotting against time the cumulated terrace elevations and the average elevation of the Santernian coastline in the investigated area, we detect rates of uplift during the last 1.8 Ma. Two major pulses of uplift are recognized 0.86 through 0.5 Ma, and 0.25 Ma through the Present, which are interpreted as driven by the subduction process and uprising of metasomatized magma bodies on the Tyrrhenian Sea Margin of central Italy, superimposied on a smaller isostatic component of uplift.
Highlights
The Tyrrhenian Sea Margin of Latium (Fig. 1), throughout the Pliocene and part of the Early Pleistocene, hosted the marine sedimentary basins produced by extensional tectonics acting at the back of the Apennines orogenic belt[1, 2]
In the present work we have adopted the same methodological approach employed by[12] in the coastal area between Civitavecchia and Anzio and in the inland area of Rome, to reconstruct a suite of paleo-surfaces occurring at different elevation along the inner portion of the Tyrrhenian Sea margin comprised between Magliano Sabina and Rome (Fig. 1), and to correlate them with the marine isotopic stage (MIS) timescale, providing an indirect age for each terrace
Assuming that regional uplift has been active since 1.8 Ma, a smaller uplift rate is inferred in the time span 1.8–0.8 Ma with respect to that estimated in the following period, suggesting that the uplift on the inner Tyrrhenian margin during the last 0.8 Ma comprises the combination of the early steady trend and the trend observed near the coast amended from local tectonic subsidence
Summary
Received: 31 January 2017 Accepted: 6 April 2017 Published: xx xx xxxx arc magmatism-related uplift in central Italy. A larger paleo-surface ranging 201–220 m a.s.l. is recognized (red triangles in Fig. 4a) and interpreted as the oldest terrace in this area, corresponding to an early coastal plain of late Santernian-Emilian age (S in Figs 4a and 5a,b) This paleo-surface onlaps (“rubine” red and violet contour lines in Fig. 4a) on the older Gelasian continental deposits (G in Figs 4a and 5a) and on the carbonate structure of the Apennines, while it is poorly preserved (pink triangles) closer to the Tiber valley, where a suite of younger terraced surfaces and a related aggradational succession is present. The two lowest fluvial terraces of[10], according to the geochronologic constraints provided by these authors, correspond to those of MIS 7 and MIS 5, which have marked morphological evidence in the whole hydrographic network of the Tiber River, due to the occurrence of the most recent pulse of uplift since 250 ka[12]
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