Distribution in space and time and analysis of ...€¦ · for the regional stratigraphical reconstruction, but neither the volcanic activity of the Albano and Sabatino districts

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1. SPATIAL DISTRIBUTION OF THE SITES

The aim of the present contribution is to offera general overview of the distribution of theLower Palaeolithic sites - with both bones andartefacts- of the surroundings of Rome (Fig. 1),moreover to trace some regularities in their spa-tial distribution and to analyse some of the fac-tors that may have played a role in their preser-vation and discovery. Geological characteris-tics and discovery conditions of 12 major sitesare given in table I (a, b).

According to the site distribution in relationto the geological context, the older sites (age

about 300,000 years) are predominantly relatedto the fluvio-lacustrine environment existingtowards the end of the main volcanic activity ofthe Albano and Sabatino districts (MiddlePleistocene, between about 500,000 and300,000 years BP). Instead, the younger sites(age 200,000 - 125,000 years) are related pre-dominantly to a plainly alluvial environment.In the older group, present altitudes are higherthan in the younger group (60 to 70 m a.s.l. –with Torre in Pietra “m” as an exception - ver-sus 30 to 50 m a.s.l.). One notices that half ofthe sites were discovered after 1970 (mainlythose belonging to the older group).

Distribution in space and time and analysis of preservationfactors of Pleistocene deposits in the Roman area

A. Arnoldus-Huyzendveld1, F. Zarlenga2, P. Gioia3, M.R. Palombo4

1Digiter S.r.l., Rocca di Papa (RM), Italy - [email protected] 2ENEA/CR-Casaccia-Divisione CAT, Roma, Italy - [email protected] Comunale ai Beni Culturali, Roma, Italy - [email protected] di Scienze della Terra, Università degli Studi di Roma “La Sapienza”;CNR, Centro di Studio per il Quaternario e l'Evoluzione ambientale, Roma, [email protected]

SUMMARY: An overview is given of the distribution of the 12 major Lower Palaeolithic sites around Romewith both bones and artefacts. Regularities in their spatial distribution are traced, and the preservation and dis-covery conditions of the sites are analysed. Generally, the formation of the embedding sediments is recog-nised as a principal site-forming condition. It is stressed that in the “Campagna Romana”, sedimentary con-ditions have been present only during very short periods of the Quaternary geological evolution. Also otherfactors for site “formation” -favourable living conditions, burial, fossilisation, and discovery- are analysed forthis specific area. It is concluded that the present distribution of Lower Palaeolithic sites near Rome may bemainly due to events related to the local and regional geological and morphological evolution. It is remarkedthat, in order to gain insight in the real areas of frequentation of the “Campagna Romana”, one should takeinto account all the factors relevant to site formation, in particular the existence of favourable depositionalconditions only during short time spans, the Quaternary landscape evolution characterised by several inter-twined cycles of erosion and sedimentation, and the spatial distribution of stratigraphies containing remainsand their apparently similar empty counterparts.

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2. A CONDITION FOR SITE-FORMATION:EMBEDDING IN SEDIMENTS

An essential site forming condition is the for-mation of the embedding sediment. From theviewpoint of landscape development, to survivein time, the remains should be embedded in themost recent cycle of deposition, or in relictsfrom older cycles that escaped later erosion.Moreover, the deposit should be located in sucha position in the present landscape that thedepth below the surface allows for discovery(Arnoldus-Huyzendveld 1995).

The sediments of the Middle Pleistocene(middle and late) of the “Bassa CampagnaRomana”, represented by the alluvial sedi-ments of the Tiber river and its complex tribu-tary system, are clearly related to the eustaticrise of the sea level at the moment of deglacia-tion and represent complete sedimentary cycles(Malatesta & Zarlenga 1986, 1986a, 1988).Their position, at least concerning the threeoldest cycles (formations of San Cosimato,Aurelia and Vitinia; Conato et al. 1980), did notgive rise to alluvial terraces in the strictersense, since no uplift phases occurred duringtheir deposition. Being the later fills inset in thetrenches cut in the earlier fills, these sediments

can be identified as “alluvial fills inset”(Leopold et al. 1964). They are separated byerosion surfaces of global character, related tothe eustatic lowering of the sea level in coinci-dence with glacial phases (Caloi et al. 1998).

Examining the most recent sedimentarycycle, represented by the present Tiber flood-plain deposits, with a thickness variablebetween 100 m near the sea and about 50-60m near the city of Rome, we observe that theselayers were deposited between 12000 and8000 years ago. This means that an alluvialinfill was produced in only 4000 years; thisvalue can be enlarged when admitting a rea-sonable margin of error, but anyway a veryshort time stands out.

Reflecting upon the fact that, in the past, allu-vial infills of this type have been considered tocoincide with the entire interglacial part of aglacial-interglacial cycle (the whole cycle last-ing on average about 100,000 years), onenotices that from the record of the interglacialphase a large part of possible information con-tained within the sediments is lacking.Therefore, a fluvial sedimentary cycle in areasclose to the river outlet, like the “BassaCampagna Romana”, does not represent elsethen a small part of a much longer story.

Distribution in space and time and analysis of preservation factors of the Pleistocene deposits

Fig.1 - Distribution of the major Lower Paleolithic sites around Rome.

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Tab.1a - Discovery- and site characteristics of the principal Lower Palaeolithic sites around Rome.

Tab.1b - Discovery and site characteristics of the principal Lower Palaeolithic sites around Rome (continued)

And moreover, that part is limited to inter-glacial climatic conditions, since the eventuallyexisting remains refering to glacial periods arenow covered by the sea.

There occur also sediments, mainly lacus-trine, but also alluvial, e.g. alluvial floodingdeposits, which are detached from this specificevolutionary context, i.e. detached from theoutcrops of the “alluvial fill inset”, and forwhich it has been possible to reconstruct adetailed evolution. Frequently, just in thesecontexts paleontological and palethnologicaldifferences of a certain extent are observed, andsensible differences between the industries ofvarious outcrops or differences in the faunasare evaluated. Here the request arises to refinethe geological time scale. But from the geolog-ical viewpoint it is not possible to define a dif-ferent reference period since the event is thesame, i.e. the rising and highstand of the sealevel, and almost never one succeeds in under-standing the exact point on the time line of theevents.

A particular limitation of the “CampagnaRomana” is moreover the absence of limestoneoutcrops and the consequential lack of caveswith archaeological and faunal remains.

Volcanic layers represent precious markersfor the regional stratigraphical reconstruction,but neither the volcanic activity of the Albanoand Sabatino districts has been continuous (DeRita et al. 1991; 1993; De Rita & Zarlenga, thisvolume). The activity started about 500,000years ago and lasted until about 25,000 yearsago, with very long periods of inactivity.Therefore, also the information contained involcanic products, or in the sediments derivedfrom them, are limited to precise moments ofthe regional evolution. For instance, one shouldconsider (De Rita et al. 1993) that the majorpart of the activity and the products of the“Tuscolano-Artemisio” period of the Albanovolcanic district seems to be deposited duringphases of low sea level.

One must conclude that the information con-tained in sediments, and thus it paleontologicaland palethnological content, does not evidenceanything else than particular moments of muchlonger lasting geological events, about which

we have no, or very few, information. Certainly,once cleared up this limitation of geology it ispossible, by integrating the various informa-tion, to succeed more or less correctly in deter-mining the point on the time line of a specificsite.

3. OTHER CONDITIONS FOR SITE FORMATION

3.1 Favourable living conditions

We may presume that the peculiar environ-mental conditions of the Rome area, surround-ed by volcanoes that were during the LowerPalaeolithic in their “afterlife”, must have exer-cised a general attraction on the mammal fauna.One could mention the abundant vegetation onfertile soils, the abundance of springs and watercourses, the complex pattern of environmentalconditions, the ease of tracking from one areato another caused by the levelling effect of thepyroclastic deposits – absence of steeply dis-sected valleys-, the presumable dominance ofintermittent parallel river channels (of the“braided” type) related to the high sedimentload of the water courses, and the frequentoccurrence of stagnant waters so typically for a“young” geomorphology.

3.2 Burial and fossilisation

Taphonomy analysis provide a convenienttool to detect how fossils form and why theyare found where they are (Andrews 1997;AA.VV. 1999; Martin 1999). As alreadyknown, the possibility to have bone–bearingdeposits depend on nature of the organism, wayand place of life and manner and cause ofdeath, nature of biotic and physical processesoperating during transport, burial and fossilisa-tion, nature of deposit, processes of accu-mulation and of diagenesis of remains.Consequently, the bone-bearing deposit forma-tion is not an usual phenomenon and a bonerecord rarely samples more than a very smalland more or less poorly representative selectionof an animal community (Behrensmeyer 1991).Any way, bones, made by complex matrix ofproteinaceous materials (collagen and others),

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Distribution in space and time and analysis of preservation factors of the Pleistocene deposits

highly mineralised and reinforced with hydrox-yapatite (Ca10[PO4]6[OH]2 ) are usually the lastpart of the vertebrate body to decompose andare often robust enough to survive and fossilise.Preservation is aided by the relative resilienceof bone, which provides improved opportuni-ties for chemical alteration and fossilisation(Trueman & Benton 1997). However, bones aresubject to destruction through breakage due totransport, trampling, scavenging, digestiveprocess, weathering, wetting and drying, acidconditions etc.

Rapid burial is a near essential for bonepreservation. This is usually accomplished influvial, lacustrine or marine environmentsthough there can preservation in terrestrial sitesunder suitable chemical conditions. Caves, ashoriginating from volcanic eruptions and vul-canoclastic deposits can also offer conditions inorder to a potential preservation. Fluvial condi-tions notably affect by selective transport thecomposition of bone-bearing. In fact, the trans-port of bone to sites of deposition are governedby the same rules which control movement ofother sedimentary particles. In many instances,bone beds develop on river bends or other siteswhere clasts accumulate. This is the pattern ofmany deposits of the “Campagna Romana”.

In the “Campagna Romana”, bone fossilisa-tion has presumably occurred in most casesthrough calcification. Although few analysis onthe chemical composition of the bones are pub-lished, one could infer this from the composi-tion of the circulating groundwater, which isfrequently calcareous through the influence ofthe sandy calcareous layers interbeddedbetween the clayey Pliocene substrate and thevolcanic deposits.

A special case of fossilisation is present atthe La Polledrara site, i.e. evidently throughfluoritisation (Arnoldus-Huyzendveld &Anzidei 1993; Anzidei et al. in press). Thecomposition of the bones has been determinedby diffractometric analysis as fluoroapatite, aresistant and hard material. The bone remainsare frequently associated with small fluoriticaggregates and more rarely, with large imprintsof radial gypsum crystals. The local lacustrinesediments are made up mainly of ashy tuffites.

Within these sediments there occur occasional-ly whitish layers, composed mainly of fluorite(also barite and halite are present as minerals).

The origin of these layers has been related tothe rise along fractures of mineralised fluidscausing fumaroles at the surface. Volcanic gasmay mix with ash, and fluorine may link to theash particles. The process of fossilisation mayhave occurred by indirect contact of the boneswith ashes and fluorine-containing water. Thechemical transformation must have been of thistype: hydroxyapatite + F <––> fluoroapatite +OH. The gypsum (CaSO4) could be a result ofthe interaction of the bone calcium with the sul-phur contained in the fluids or gasses.

The distribution of fluorite layers in the localgeological context turned out to be limited to anarrow N-S belt with a length of more than 10km, crossing the site. Therefore, this kind offossilisation may have occurred as well in othersites situated on this belt (Castel di Guido, ViaAurelia, Boschian 1993). The fluorite depositsof the Rome area are a rather rare phenomenonif seen on a world scale, so probably also thisway of bone fossilisation.

3.3 Discovery of the sites

Urban or suburban conditions do evidentlycontribute to the discovery of archaeologicalsites. The discovery conditions of the sites ofthe “Campagna Romana” were essentially oftwo kinds: or in relation to intensive surfacetransformation through quarries or publicworks or to more or less systematic surveys.The two types of discovery tend to concentratein two different sectors of Rome: the former inthe north-eastern area (Casal de' Pazzi, Sediadel Diavolo, Monte delle Gioie, Saccopastore,Ponte Mammolo) and the latter in the area tothe west of the town, close to the Via Aurelia(Torre in Pietra, Castel di Guido, Malagrotta,La Polledrara di Cecanibbio, Via Aurelia km.19,3). This distribution is related to the recentdevelopment of these areas. From the end ofthe 19th century on, the eastern zone has beensubject to urbanisation, with the gradual substi-tution of the existing gravel and sand quarriesby urban quarters. On the contrary, a vast area

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to the west was composed by large estatesbelonging to the “Pio Istituto di S. Spirito” andthe “Ospedali Riuniti di Roma”, which wereused as agricultural estates and farms for sup-plying the Roman hospitals. These propertiespassed in 1978 to the Rome Municipality andwere from then on protected by the UrbanDevelopment Plan, thus maintaining their agri-cultural vocation.

Another aspect typical of the Rome area isthe presence of many Institutions related to thearchaeological heritage. We should mentionresearch Institutes like the “Istituto Italiano diPaleontologia Umana”, the University of Pisaand particularly the survey activity and capil-lary archaeological research and protectionactivity of the Rome territory by the“Soprintendenza Archeologica” of Rome. So ithas been possible to exercise a control on theterritory and to verify constantly the strati-graphical situations and the archaeologicalpresences put to light during the expansion ofthe city. The result of this policy has been theidentification, excavation and preservation, oftwo of the most interesting late MiddlePleistocene deposits in Italy: the La Polledraraand the Casal de’ Pazzi sites, as well as theacquisition of many data useful for a detailedgeomorphological and palaeo-environmentalreconstruction of the Rome territory.

4. CONCLUSIONS

Referring to the present distribution of theearly Palaeolithic sites in the Rome territory,one notices that a few stratigraphical situationsare dominant, i.e. alluvial and volcanic-lacus-trine.

From the geological considerations exposedit follows that sedimentary conditions musthave dominated only during a small portion of time, i.e. the phase of sea level rising.Moreover, natural caves that eventual could fillsome of the gaps in our knowledge are lackingin the “Campagna Romana”. And finally, theknown data are limited to interglacial climaticconditions, since the eventually existingremains refering to the glacial periods are nowcovered by the sea or have been removed by

surface erosione. Considering moreover theother conditions necessary for becoming a site(frequentation, burial, fossilisation and discov-ery), it may be justified to conclude that thepresent distribution of Lower Palaeolithic sitesnear Rome is probably due mainly to fortunatesequences of events related to the local andregional geological and morphological evolu-tion. In particular one could refer to the condi-tions that the top of the volcanic-lacustrine sed-iment layers (with locally favourable fossilisa-tion conditions for the faunal remains) becameexposed through the late Pleistocene andHolocene surface erosion, and that in the lowertract of the Aniene River, the terraces werelocally well preserved trough the combinedinfluence of lateral river displacement (sealevel highstand) and linear dissection (lastsealevel lowstand).

It must be stressed that, due to the intensiveurbanisation and the constant presence of theinstitutions, in the “Campagna romana” manypotential “containers” have been observed, i.e.those stratigraphies that may have had thepotential to embed and preserve the paleonto-logical and associated archaeological remains.But almost never these turned out to be present.

Taking into account the existence offavourable local depositional conditions onlyduring short time spans and the (complementa-ry) huge gaps in time and space, moreover aQuaternary landscape evolution characterisedby several intertwined cycles of erosion andsedimentation, and finally the spatial distribu-tion of “empty” stratigraphies and of stratigra-phies containing remains, it should well be pos-sible to gain insight into the real areas of fre-quentation.

5. REFERENCES

AA.VV. 1984. I primi abitanti d’Europa.1.500.000 – 100.000 anni. Catalogo dellamostra. Ministero per i beni culturali eambientali, Soprintendenza speciale almuseo preistorico etnografico “LuigiPigorini”. Roma: De Luca.

AA.VV. 1999. Taphonomy as a tool inpalaeoenvironmental researches and envi-

15

Distribution in space and time and analysis of preservation factors of the Pleistocene deposits

ronmental assessment. Palaeogeography,Palaeoclimatology, Paleoecology, 49, spe-cial issue.

Andrews, P. 1997. What Taphonomy can andcannot tell us. Quadernos de GeologiaIberica 23: 53-72.

Anzidei, A.P., Angelelli, F., Arnoldus-Huyzendveld, A., Caloi, L., Palombo, M.P.& Segre, A.G., 1989. Le gisementPleistocène de la Polledrara di Cecanibbio(Rome, Italie). L'Anthropologie, XCIII, 3:749-781.

Anzidei, A.P. & Arnoldus-Huyzendveld, A.,1992. The middle Pleistocene site of LaPolledrara di Cecanibbio (Rome, Italy).Fourth Conference of Italian Archaeology,B.A.R., I.S.: 141-153.

Anzidei, A.P., Arnoldus-Huyzendveld, A.,Lemorini, L., Caloi L. & Palombo, M.R.1999. Two Middle Pleistocene sites nearRome (Italy): La Polledrara di Cecanibbioand Rebibbia - Casal Dè Pazzi; The role ofearly humans in the accumulation ofEuropean lower and middle Palaeolithicbone assemblages. Atti del Convegno tenu-tosi a Mainz, 1995: 173-195.

Anzidei, A.P., Cassoli, P.F., Ruffo, M. andSegre A.G., 1984. Risultati preliminaridello scavo di un deposito pleistocenico inlocalità Rebibbia-Casal de’ Pazzi. Atti delXXIV Convegno dell’Istituto Italiano diPreistoria e Protostoria.

Anzidei, A.P., Arnoldus Huyzendveld, A.,Caloi, L., Lemorini, C., Mussi, M. &Palombo, M.R. in press. NouvellesDonnées sur le gisement Pleistocène moyende La Polledrara di Cecanibbio (Latium,Italie). Actes du Colloque International deTautavel sur "Les Premiers habitants del'Europe" (10-15 avril 2000).

Anzidei, A.P. & Gioia, P. 1990. The lithicindustry from Rebibbia-Casal de' Pazzi. InPaper of the Fourth Conference of ItalianArchaeology, New Developments in ItalianArchaeology Part 1: 155-179.

Anzidei, A.P. & Ruffo, M.. 1985. ThePleistocene deposit of Rebibbia-Casal de'Pazzi (Rome, Italy). Papers in ItalianArchaeology IV - Part I. The Human

Landscape. Bar International Series 243:69-85. Oxford.

Arnoldus Huyzendveld, A. & Anzidei, A.P.1993. Ricostruzione di un ambiente fluvio-lacustre nella regione vulcanica di Roma(La Polledrara di Cecanibbio). Atti XXXRiunione Scientifica Istituto Italiano diPreistoria e Protostoria (Firenze 1993):151-165.

Arnoldus-Huyzendveld, A. 1995. The passageof information from the socio-cultural tothe archaeological context; aspects ofapplied soil science and sedimentology. InP. Urbanczyk (ed.), Theory and Practice ofArchaeology, part II: Acquisition of fielddata at multi-strata sites: 25-68. Warszawa.

Behrensmeyer, A.K. 1991. TerrestrialVertebrate Accumulations. In Allison, P.A.& Briggs, D.E.G., Taphonomy, 6: 291-335.

Bietti-Sestieri, A.M. (ed.) 1984. Preistoria eProtostoria nel territorio di Roma. Lavori estudi di archeologia pubblicati dallaSoprintendenza archeologica di Roma.Roma: De Luca.

Boschian, G. 1993. Castel Di Guido, scavi1980-1991. In Paleosuperfici delPleistocene e del primo Olocene in: Italia,processi di formazione e interpretazione.Istituto Italiano di Preistoria e Protostoria,Atti della XXX riunione scientifica: 167-178.

Caloi, L., Palombo, M.R. & Zarlenga, F. 1998.Late Middle Pleistocene mammal faunas ofLatium (Central Italy): Stratigraphy andenvironment. Quaternary InternationalJourn. 47-48: 77-86.

Cassoli, P.F., De Giuli, C., Radmilli, A.M.,Segre, A.G. 1982. Giacimento delPaleolitico Inferiore a Malagrotta (Roma).In Istituto Italiano di Preistoria eProtostoria, Atti della XXIII riunione scien-tifica: 531-535.

Conato, V., Esu, D., Malatesta, A. & Zarlenga,F. 1980. New data on the Pleistocene ofRome. Quaternaria 22: 131-176.

De Rita, D., Milli, S., Rosa, C. & Zarlenga, F.1991. Un'ipotesi di correlazione tra la sedi-mentazione lungo la costa tirrenica dellacampagna romana e l'attività vulcanica dei

16

The World of Elephants - International Congress, Rome 2001

17

Colli Albani. Studi Geol. Camerti, Vol.Spec.: "Studi preliminari all'acquisizionedati del profilo CROP 11. Civitavecchia-Vasto": 343-349.

De Rita, D., Milli, S., Rosa, C., Zarlenga, F. &Cavinato, G.P. 1993. Catastrophic eruptionsand glacioeustatic episodes in Latium.International Conference: "Large explosiveeruptions". Accademia Nazionale deiLincei 25/5/93, Rome.

Leopold, L.B., Wollman, M.G. & Miller, J.P.1964. Fluvial processes in geomorphology.San Francisco and London: Freeman W.H.& Company.

Malatesta, A. 1978. Torre in Pietra. Roma.Quaternaria 20: 203-577.

Malatesta, A. & Zarlenga, F. 1986.Evoluzione paleogeografico- strutturaleplio-pleistocenica del basso bacinoromano a Nord e a Sud del Tevere.Memorie della Società Geologica Italiana,

35: 75-85.Malatesta, A. & Zarlenga, F. 1986a. Cicli trasgres-

sivi medio pleistocenici sulle coste liguri e tir-reniche. Geologica Romana 25. 1-8.

Malatesta, A. & Zarlenga, F. 1988. Evidence ofMiddle Pleistocene marine transgressionsalong the Mediterranean coast.Palaeogeography, Palaeoclimatology,Palaeoecology 68: 311-315.

Martin, R.E. 1999. Taphonomy: a processapproch. Cambridge Palaebiology series 4,Library accession 560.

Radmilli, A.M. & Boschian, G. 1996. Gli scavidi Castel di Guido. Il più antico giacimentodi cacciatori del Paleolitico inferiorenell'Agro Romano. Firenze: Istituto Italianodi preistoria e Protostoria.

Taschini, M. 1967. Il "Protopontiniano" ris-siano di Sedia del Diavolo e di Monte delleGioie (Roma). Quaternaria IX: 301-319.

Distribution in space and time and analysis of preservation factors of the Pleistocene deposits