The Late Quaternary subsurface successions buried beneath several delta-coastal plains exhibit distinct cyclic facies patterns that reflect the predominant control exerted by climate-eustatic factors on sedimentation, at Milankovitch and sub- Milankovitch scales. However, local subsidence co-operates with Late Quaternary glacio-eustatic fluctuations in determining changes in accommodation space through time and space. During phases of sea-level rise (interglacial periods), subsidence further increases the accommodation space. On the other hand, during the subsequent phases of sea-level fall (glacial periods) subsidence works to mitigate the accommodation space reduction, resulting in a better preservation of the depositional record. In the case of rapidly subsiding regions, such as the Po Plain (N Adriatic Sea, Italy), the combined tectonic-eustatic effect led to a vertically stacked succession of transgressive-regressive (T-R) sequences forming a multilayered aquifer system (Amorosi and Colalongo, 2005; Amorosi and Pavesi, 2010). In a hydrostratigraphic view, sheet-like, channel-belt fluvial bodies, tens of m-thick in the regressive portion of the T-R sequences represent major aquifers. In contrast, pronounced fluvial incisions occurred during glacial periods in coastal plains characterized by lower rates of subsidence, as those facing the Ligurian- Tyrrhenian margin (e.g. Arno Plain, Ombrone Plain, Tiber Plain, Volturno Plain). These erosive processes led to the formation of km-wide and tens of m-thick paleovalleys able to erode confined aquifers, reducing their lateral continuity. In these contexts, the reconstruction of the aquifer systems is further complicated by the incised valley fill (IVF) successions formed during the subsequent interglacial periods. These IVFs, which consist predominantly of estuarine muddy deposits, represent, in fact, localized impermeable barrier to ground-water circulation. A high-resolution multiproxy approach (sedimentological, faunal and chronological data) and the application of sequence stratigraphic principles can furnish a successful threedimensional representation of such complex aquifer systems. The Arno coastal plain (Ligurian Sea, Italy) represents an ideal setting where to investigate the hydrostratigraphic role of incised valley systems (IVSs), as two well-preserved IVFs have been identified within the uppermost 100 meters and dated to two non-consecutive interglacial cycles (MIS 7 and MIS 1; Amorosi et al., 2008; Rossi et al., in press). Based on a large subsurface stratigraphic dataset, composed of hundreds of > 50 m long cores, 14C and ESR chronological data, and stratigraphic correlation, a representation of the Arno Plain aquifer system is outlined. We focused on the identification and mapping of potential aquitards/aquicludes (IVFs) and aquifers. These latter include: (i) laterally discontinuous gravel terrace deposits developed at different stratigraphic levels along the paleovalleys flanks, (ii) lenticular channel-belt sand bodies formed during the glacial phases that preceded IVSs formation, and (iii) post-valley fill coastal-marine sands showing a landward-wedging geometry. References Amorosi A. and Colalongo M.L. (2005). The linkage between alluvial and coeval nearshore marine successions: evidence from the Late Quaternary record of the Po River Plain, Italy. In: M.D. Blum, S.B. Marriott & S.F. Leclair (Eds.) Fluvial Sedimentology VII. Int. Assoc. Sedimentol. Spec. Publ. 35, 257–275. Amorosi A. and Pavesi M. (2010). Aquifer stratigraphy from the middle-late Pleistocene succession of the Po Basin. Mem. Descr. Carta Geol. d’It. XC, 7–20. Amorosi A., Sarti G., Rossi V. and Fontana V. (2008). Anatomy and sequence stratigraphy of the late Quaternary Arno valley fill (Tuscany, Italy). In: A. Amorosi, B.U. Haq & L. Sabato (Eds.) Advances in Application of Sequence Stratigraphy in Italy. GeoActa Spec. Publ. 1, 55–66. Rossi V., Amorosi A., Sarti G. and Mariotti S. (in press). Late Quaternary multiple incised valley systems: an unusually wellpreserved stratigraphic record of two interglacial valley fill successions from the Arno plain (northern Tuscany, Italy). Sedimentology.
The role of Late Quaternary incised valley systems in coastal-plain aquifer geometry: A case study from the Arno Plain (Ligurian Sea, Italy).
SARTI, GIOVANNI;
2017-01-01
Abstract
The Late Quaternary subsurface successions buried beneath several delta-coastal plains exhibit distinct cyclic facies patterns that reflect the predominant control exerted by climate-eustatic factors on sedimentation, at Milankovitch and sub- Milankovitch scales. However, local subsidence co-operates with Late Quaternary glacio-eustatic fluctuations in determining changes in accommodation space through time and space. During phases of sea-level rise (interglacial periods), subsidence further increases the accommodation space. On the other hand, during the subsequent phases of sea-level fall (glacial periods) subsidence works to mitigate the accommodation space reduction, resulting in a better preservation of the depositional record. In the case of rapidly subsiding regions, such as the Po Plain (N Adriatic Sea, Italy), the combined tectonic-eustatic effect led to a vertically stacked succession of transgressive-regressive (T-R) sequences forming a multilayered aquifer system (Amorosi and Colalongo, 2005; Amorosi and Pavesi, 2010). In a hydrostratigraphic view, sheet-like, channel-belt fluvial bodies, tens of m-thick in the regressive portion of the T-R sequences represent major aquifers. In contrast, pronounced fluvial incisions occurred during glacial periods in coastal plains characterized by lower rates of subsidence, as those facing the Ligurian- Tyrrhenian margin (e.g. Arno Plain, Ombrone Plain, Tiber Plain, Volturno Plain). These erosive processes led to the formation of km-wide and tens of m-thick paleovalleys able to erode confined aquifers, reducing their lateral continuity. In these contexts, the reconstruction of the aquifer systems is further complicated by the incised valley fill (IVF) successions formed during the subsequent interglacial periods. These IVFs, which consist predominantly of estuarine muddy deposits, represent, in fact, localized impermeable barrier to ground-water circulation. A high-resolution multiproxy approach (sedimentological, faunal and chronological data) and the application of sequence stratigraphic principles can furnish a successful threedimensional representation of such complex aquifer systems. The Arno coastal plain (Ligurian Sea, Italy) represents an ideal setting where to investigate the hydrostratigraphic role of incised valley systems (IVSs), as two well-preserved IVFs have been identified within the uppermost 100 meters and dated to two non-consecutive interglacial cycles (MIS 7 and MIS 1; Amorosi et al., 2008; Rossi et al., in press). Based on a large subsurface stratigraphic dataset, composed of hundreds of > 50 m long cores, 14C and ESR chronological data, and stratigraphic correlation, a representation of the Arno Plain aquifer system is outlined. We focused on the identification and mapping of potential aquitards/aquicludes (IVFs) and aquifers. These latter include: (i) laterally discontinuous gravel terrace deposits developed at different stratigraphic levels along the paleovalleys flanks, (ii) lenticular channel-belt sand bodies formed during the glacial phases that preceded IVSs formation, and (iii) post-valley fill coastal-marine sands showing a landward-wedging geometry. References Amorosi A. and Colalongo M.L. (2005). The linkage between alluvial and coeval nearshore marine successions: evidence from the Late Quaternary record of the Po River Plain, Italy. In: M.D. Blum, S.B. Marriott & S.F. Leclair (Eds.) Fluvial Sedimentology VII. Int. Assoc. Sedimentol. Spec. Publ. 35, 257–275. Amorosi A. and Pavesi M. (2010). Aquifer stratigraphy from the middle-late Pleistocene succession of the Po Basin. Mem. Descr. Carta Geol. d’It. XC, 7–20. Amorosi A., Sarti G., Rossi V. and Fontana V. (2008). Anatomy and sequence stratigraphy of the late Quaternary Arno valley fill (Tuscany, Italy). In: A. Amorosi, B.U. Haq & L. Sabato (Eds.) Advances in Application of Sequence Stratigraphy in Italy. GeoActa Spec. Publ. 1, 55–66. Rossi V., Amorosi A., Sarti G. and Mariotti S. (in press). Late Quaternary multiple incised valley systems: an unusually wellpreserved stratigraphic record of two interglacial valley fill successions from the Arno plain (northern Tuscany, Italy). Sedimentology.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
