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Featured article from geoscience journal

Geografia Fisica e Dinamica Quaternaria, 2012, Issue 35, p. 119-127
Landscape evolution in the Tacchi area (Central-East Sardinia, Italy) based on karst and fluvial morphology and age of cave sediments


The east-central part of Sardinia (Italy) is characterised by Jurassic

dolomitic mesas (Tacchi, or «table mountains») that overlie a Palaeozoic

basement mainly composed of metavolcanics and phyllites. These mountains

are the remnants of a continuous carbonate cover, dissected by

faults and river erosion, and are now completely isolated hydrological

systems. Most of these rivers have cut valleys more than 200 metres deep

into the Palaeozoic basement rocks, whose slopes are often characterised

by landslides, suggesting their recent oversteepening. Some valleys, on

the contrary, have not reached the base of the carbonate sequence and

appear to be suspended above the deeper incisions, apparently disconnected

by them. Several subhorizontal surfaces can be distinguished on

the table mountains, related to local base level stillstands. Also water

table caves, scattered along the flanks of the mountains over an altitudinal

range of about 200 m, show several stillstands in base level lowering.


26Al and 10Be burial dating of sediments in four caves located at different

elevations on the flanks of the suspended Taquisara Valley show

an Upper Pliocene or Lower Pleistocene age. Thus, this valley appears to

be of Late Tertiary age. The deeper valleys, such as Riu Pardu, that dissect

the Tacchi mountains completely, cutting deeply into the basement

rocks, are much younger, as their unstable slopes suggest. Knickpoint retreat

in Riu Pardu and estimated valley erosion rates suggest the capture

of Riu Pardu by Rio Pelau to have occurred in the last 100 ky.