Upper Agri Valley (Basilicata) Between Geomorphology and Ancient Settle- Ments
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Upper Agri Valley (Basilicata) between Geomorphology and Ancient Settle- ments Francesco Tarlano Sapienza Università di Roma, PhD student email: [email protected] Julian Bogdani Alma Mater Studiorum - Università di Bologna email: [email protected] Antonio Priore Freelance professional geologist email: [email protected] Abstract 1. Introduction In this paper we present the geoarchaeological The Upper Agri Valley is placed in the mountain and landscape project on the Upper Agri Valley area of an inland Lucania valley that cuts the (Basilicata). Between 2012 and 2015 we coordi- region from west to east, up to the river that flows nated multidisciplinary research with the purpose into the Ionian Sea. For this reason, the valley of reconstructing the history and evolution of the floor has been an essential route between the territory, analysing the relationships between man two coasts (Tyrrenian and Ionian coast) since the and landscape from the Prehistory to the Middle ancient times. This area is archaeologically known Age. The studied area, an inland mountain valley primarily for the existence of the important Roman situated in the ancient Lucania, is very important, town of Grumentum. It settlements in the country- because it is a fundamental route between the two side are less well known because archaeological coasts of Magna Graecia and because during the investigations have mainly been focused on urban- Roman period this valley was the territory in which istic questions. Grumentum was born, one of the most important Indeed, the area has been studied since the towns of Roman Southern Italy. Thanks to the dia- second half of the 1960s, especially for questions logue between different competences, this project concerning the city of Grumentum. The landscape, aims at understanding the settlements dynamics instead, has never been studied, except when the and the mutual influences between man and en- Soprintendenza has to make inspections during vironment: indeed, we conducted geophysics and building constructions. Therefore, in this con- geoarchaeological investigations, archaeological text, we have created a research project with the surveys, cartographic and aerial photos studies, Ancient Topography teaching post of University written sources analysis: in this way, different of Bologna (directed by P. L. Dall’Aglio and E. data are used to understand the landscape from a Giorgi), in cooperation with Sapienza University global point of view. of Rome. This project purposes to reconstruct the ancient settlements order as well as the Keywords: Agri, Grumentum, Topography, Lucania, landscape morphology and evolution during the Geoarchaeology centuries. LAC2014 Proceedings | DOI 10.5463/lac.2014.57 1 Since 2012, we directed on the field a series ders lower and closer to the river (Tarlano, 2013: of multidisciplinary studies, with archaeological 233-40). For what concerns the river flow, we can surveys in the districts of Grumento Nova and underline a migration of the river bed from north Viggiano and geoarchaeological research (geo- east to south west, produced by the sediments of physics, pollen analysis, etc.) aimed to under- the alluvial fans from the southern slopes of the stand the geomorphological units preferential Volturino chain. for ancient settlements and to reconstruct the Thanks to the analysis of the valley, we can paleoenvironmental aspects. The interaction and note a constant evolution of meandering, much the dialogue between competences usually oper- more evident in the area upstream and west of ating in different fields allows the proposition of a Grumentum. In the east area, however, the river global interpretation of the historic understanding has an anastomosed path near the Lake Pertusil- of a landscape, as a result of natural events and lo and, going to the east, the river flows deeply human actions, and mutual relations between the embanked. The different morphological nature of two causes. In this paper, we want to introduce the the river bed is conditioned by the territory, and by research methodologies used during our project lithologies and tectonics, that influence the whole of territorial archaeology and the first results of region. these investigations. (F.T.) We studied the geomorphology of the valley, starting with a field survey and then we arranged some investigations with the purpose of identify- 2. Geological and Geomorphological ing the underground structures related to other Research: The Geoarchaeological Investi- depositional events. For instance, we found some gations paleo channels of the river Agri, that testify to the evolution and migration of the river bed. We The Agri valley is an intermountain basin of the used Electrical Resistivity Tomography (ERT), very Southern Apennines, full-formed by tectonics useful for the identification of natural or anthropic in the Quaternary period, bounded by border or interred structures. direct faults with Apenninic direction, filled by Near the ERT stringings, we dug with an alluvial sediments, and defined by reliefs made excavator some sample tests, useful to propose of geological formations of limestone belonging a stratigraphic analysis of the first metres under- to Carbonate Platform Units over the Lagonegro ground. The stratigraphy allowed to us to identify Units made by basinal silico-calcareous marl. The the last depositional events in the area, consid- tectonics created the conditions for the valley’s ering the distribution and the depth of the layers. disposition; the plio-pleisticenic lake basin gradu- During the excavation, we also collected some ally dried up due to the opening of a dam threshold samples for pollen analysis and for radiocarbon for natural tectonic causes (Priore, 2010: 11-19). dating, for a vegetational and paleoenvironmental The valley is quite flat, but its uniformity is interpretation of the data. interrupted by alluvial fans and stream terraces Moreover, we studied the aerial photos from (that testify to the alluvial activity of the area) and different periods: in fact, we noted a lot of differ- by predominantly limestone hills. The alluvial ences in the landscape between the first flight fans are easily distinguishable on the base of the (1951) and the current flights, especially in terms southern slopes of the Volturino – Monte di Vig- of the river Agri flow, the woods’ coverages and giano mountain chain. The east area of Upper Agri the alluvial shapes. Valley, close to Lake Pertusillo, is flat but terraced In the geomorphological survey, the prelimi- with high borders. On the west side, northwest nary activity of aerial photos analysis is fundamen- from the hill of Monticello, Tramutola, the river tal to point out the shapes of a landscape in the engraving is less clear with the terraces’ bor- third dimension. The study of 1951 aerial photos 2 LAC2014 Proceedings | DOI 10.5463/lac.2014.57 Fig. 1. Excerpt from the Geomorphological Map of the Upper Agri Valley (top); physical geography of Basilicata and localisation of the studied area (bottom). LAC2014 Proceedings | DOI 10.5463/lac.2014.57 3 Fig. 2. Evolution of a landscape. (top): excerpts from the allows us to find interesting elements of the paleo aerial photos (1951 and 2003); (bottom): a Geo-electrical environments. In fact, thanks to the ERT, we veri- section with the Agri river and some paleo-channels. fied the repositioning of the Agri river bed; further- more, in some cases, the results permitted us to locate some very interesting anomalies, attributa- ble to interred ancient buildings. with the stereoscope, and their overlap with the The sample excavations pointed out the surface current photos, allowed us to understand how geology and stratigraphy in which it’s been possi- the river bed changed its path. So, we found that ble to distinguish sedimentary and granulometric the alluvial fans are still dynamic, and that they patterns and the particle disposition. The descrip- carried out sediments in the Agri basin quickly tion of the stratigraphic elements allowed us to and violently, before the building of the river bank reconstruct the energy transport and depositional and other hydraulic control structures. The wood environments and to recognise any anthropic coverage also was different in 1951, less wide than element. The regular samples collection on the now. In the end, the aerial photos helped us in exposed surface of the excavation has been useful the identification of anthropic interred structures, to analyse pollen in layers dated by radiocarbon. thanks to the stereoscopic vision. The pollen analysis is based on the extraction, ERT exploits the features of the material to identification and interpretation of pollen grains be crossed from the electricity, so any resistivity found in the samples. Basically, with the analysis anomaly is linked to interred objects. The data of the pollen grains, we can compile a list of plant processing, together with a geological research, life useful for the paleo vegetation reconstruc- 4 LAC2014 Proceedings | DOI 10.5463/lac.2014.57 tions and for the identification of anthropogenic gated with good resolution were those fields with elements, explaining the relationship between average visibility, fields that because of low or man and environment. During our first analysis, absent vegetation, allow an easy identification of the samples have been particularly poor of pollen, mobile finds or structures on their surface, even with little pollen grains and few palynomorphs. if they weren’t ploughed in depth. The areas that, The discovery of some pollen grains of cereal was for various reasons, (the most common due to very interesting, meaning an important presence the presence of fences or high and dense vegeta- of this plant in the fields all around Grumentum. tion) do not allow the immediate identification of A.P. artefacts and structures, generally they haven’t been visited. This choice reduced the investiga- ble and investigated areas within the test area; 3. Archaeological Investigations: The Re- however, it also has ensured good reliability of the search Methodology and the Data Man- data (presence or absence of artefacts or struc- agement tures) for the investigated areas.