The planning of every defense project in a sandy coast demands to know how dynamic pro."rró. affecting the coast act and, particularly, how the sedimentary supply, cómirrg from fluvial input,-is distributed along the coast by littoral drifts' Beside welltestedLethodologies turned to the definition of the longshore sediment-flow (e.g. petrographic and ìextural analysis ofthe sands or artificial drifter-launch) less traditional meth;ds, like geochemical analysis of the sediment and the study of bio-drifters can be used. This paper presents the preliminary results of a research carried out on the coast of pisa and ruipori"a by Provincia of Pisa. Fossil foraminifers, picked from sandy samples, were used às natural drifters in order to define longshore sediment flows. Samples were collecteda t severald epthsa long transectsn ormal to the shore,f rom the foreshorez one to the shoreface zone up to the isobate of -10 meters. The costal area between Arno and CalambroneR iversw as samPled. Two main groups of fòraminfera were distinguished: i) well preserved pliocenic foraminifers without any evidence of recrystal\zation and ii) bad preserved and recrystallizedp re-pliocenicf oramiferers. The first assemblageis characterizedby the presenceo f Globorotalia puncticulata andG lobigerinoides, lb"r-elongotus gr. while Paleocene-Eocen(ee g. Morozovella and Acarininal and Miocene (eg. Gtobigerinoides spp., Dentoglobigerina altispira gt) taxa prevail within the second assemblage. The preliminary resultsi ndicatet hat the first group exclusivelyc haracterizesth e seaareab etweenS colamatoreR iver and Calambronev illage while the secondo ne develops along the coastal zone between Arno River and Tirrenia village. In order to know the feed area of these two foraminiferal assemblagesa dditional samples were collected in Amo and calambrone rivers. The acquired data indicate that the Èliocenicf oramifersa re carriedb y CalambroneR iver while pre-Pliocenica ssociations are typical of the sandst ransportedb y Arno River. Therefore,t he presenceo f a northward drift'(from Calambrone Riveì to Calmbrone village) and of a southward drift (from Arno Rivei to Tirrenia village) can be infened and reveals a drift-convergence zone, in agreemenwt ith the resuliso f previousw orks basedo n different methodologies' In conclusion,t he use ofloramiferal assemblagetso define longshores ediment-flows seemst o be a very promisingt ool, particularly in coastalz onesf ed by fluvial systemst hat drain different alimentation areas.
The use of foraminiferal tests as bio-drifters: a new tool to define longshore sediment flows. An example from Pisa coast (Tuscany, Italy)
SARTI, GIOVANNI
2007-01-01
Abstract
The planning of every defense project in a sandy coast demands to know how dynamic pro."rró. affecting the coast act and, particularly, how the sedimentary supply, cómirrg from fluvial input,-is distributed along the coast by littoral drifts' Beside welltestedLethodologies turned to the definition of the longshore sediment-flow (e.g. petrographic and ìextural analysis ofthe sands or artificial drifter-launch) less traditional meth;ds, like geochemical analysis of the sediment and the study of bio-drifters can be used. This paper presents the preliminary results of a research carried out on the coast of pisa and ruipori"a by Provincia of Pisa. Fossil foraminifers, picked from sandy samples, were used às natural drifters in order to define longshore sediment flows. Samples were collecteda t severald epthsa long transectsn ormal to the shore,f rom the foreshorez one to the shoreface zone up to the isobate of -10 meters. The costal area between Arno and CalambroneR iversw as samPled. Two main groups of fòraminfera were distinguished: i) well preserved pliocenic foraminifers without any evidence of recrystal\zation and ii) bad preserved and recrystallizedp re-pliocenicf oramiferers. The first assemblageis characterizedby the presenceo f Globorotalia puncticulata andG lobigerinoides, lb"r-elongotus gr. while Paleocene-Eocen(ee g. Morozovella and Acarininal and Miocene (eg. Gtobigerinoides spp., Dentoglobigerina altispira gt) taxa prevail within the second assemblage. The preliminary resultsi ndicatet hat the first group exclusivelyc haracterizesth e seaareab etweenS colamatoreR iver and Calambronev illage while the secondo ne develops along the coastal zone between Arno River and Tirrenia village. In order to know the feed area of these two foraminiferal assemblagesa dditional samples were collected in Amo and calambrone rivers. The acquired data indicate that the Èliocenicf oramifersa re carriedb y CalambroneR iver while pre-Pliocenica ssociations are typical of the sandst ransportedb y Arno River. Therefore,t he presenceo f a northward drift'(from Calambrone Riveì to Calmbrone village) and of a southward drift (from Arno Rivei to Tirrenia village) can be infened and reveals a drift-convergence zone, in agreemenwt ith the resuliso f previousw orks basedo n different methodologies' In conclusion,t he use ofloramiferal assemblagetso define longshores ediment-flows seemst o be a very promisingt ool, particularly in coastalz onesf ed by fluvial systemst hat drain different alimentation areas.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
