STRUTTURA FISICA DELLA CONOIDE ALLUVIONALE GIGANTE DEL FIUME TARO E RICARICA DEGLI ACQUIFERI DELLA PIANURA PARMENSE

Abstract

Bedulli F. & Valloni R., Physical structure of the Taro River giant alluvial fan and Parma plain aquifer recharge. (IT ISSN
0394-3356, 2004).
Using a large set of stratigraphic data, numerous cross-sections of the southern margin of the Parma alluvial plain were drawn; they
allowed the recognition of the architecture of the Taro alluvial fan and the water flow pattern from the surface to the unconfined and
confined aquifers.
The middle (Medesano-Madregolo) and outer portion of the alluvial fan system are separated by an anticline, named Madregolo high,
which controls the groundflow pattern with its impermeable basement uplifted at about -70 m from ground level. In its outer portion
the fan has giant dimensions extending up to 15 km axially and up to 20 km normally to the depositional strike.
The sedimentation of the Middle-Late Pleistocene alluvium is strongly related to climatic changes. General and local evidence permit
the assignment of the tens of meter thick coarse fluvial deposits to cold (glacial) periods and of the meters thick fine alluvium to warm
(interglacial) periods.
The base of the alluvial fan rests on a laterally continuous confining layer dated 180.000 yr BP. At the intersection Taro River -
Autostrada A1 this layer is encountered at -130 m from ground level; confining layers of lesser importance, internal to the alluvial fan
body, are encountered at -40 and -80 m from ground level.
In front of the Madregolo high the coarse sedimentary units (aquifers) of the alluvial fan body are amalgamated. Northwards these aquifers expand in thickness and are put under pressure by the intervening confining layers. This indicates that the groundwater flow pattern is from the front of the Madregolo high northwards into the unconfined and confined aquifers of the thickest part of the fan.