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The site of Coste San Giacomo (Early Pleistocene, central Italy): Palaeoenvironmental analysis and biochronological overview
Quaternary International 267 (2012) 30e39
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The site of Coste San Giacomo (Early Pleistocene, central Italy): Palaeoenvironmental analysis and biochronological overview Luca Bellucci a, *, Ilaria Mazzini b, Giancarlo Scardia c, Luciano Bruni a, Fabio Parenti a, Aldo Giacomo Segre a, Eugenia Segre Naldini a, Raffaele Sardella d a
Istituto Italiano di Paleontologia Umana, Piazza Mincio 2, I-00198 Roma, Italy IGAG-CNR, Via Salaria Km 29.3, CP 10, Monterotondo Staz., I-00016 Roma, Italy INGV, Sezione di Milano-Pavia, via Bassini 15, I-20133 Milano, Italy d Dipartimento di Scienze della Terra, “Sapienza” e Università di Roma, P.le Aldo Moro 5, I-00185 Roma, Italy b c
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 15 April 2011
Facies and ostracod analyses have been performed on a continental core drilled at Coste San Giacomo (Anagni, central Italy), where a middle Villafranchian faunal assemblage was first discovered in 1978. The core intercepted the palaeontological level and penetrated the underlying sedimentary succession, previously largely unknown, for a total sediment recovery of 40 m. In addition, new field surveys led to the discovery of Hippopotamus sp. remains at the faunal site, thus pre-dating the dispersal of this large ungulate into Europe to the middle Villafranchian. The new sedimentological and palaeoecological data allowed to define a palaeoenvironment mainly ascribable to an alluvial plain, characterized by a marsh evolving into a floodplain with overbank deposits and a sand-bed fluvial-channel. This scenario is supported by the reassessed Coste San Giacomo faunal assemblage, consistent with running and/or clear waters as well as prairies and grasslands, under mild climatic conditions. Ó 2011 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction The PlioceneePleistocene (PiacenzianeGelasian) boundary, constrained at 2.588 Ma (Rio et al., 1994; Gibbard et al., 2010) and approximated by the GausseMatuyama polarity reversal (2.581 Ma; Lourens et al., 2005), straddles a global cooling trend between marine isotope stage (MIS) G2 to 100 (Lisiecki and Raymo, 2005) and culminating with the onset of obliquity-driven glacial/ interglacial cycles typical of the Early Pleistocene (Shackleton, 1995). This global cooling trend is temporally associated with the demise of Pliocene ecosystems and the spread of fauna and flora associations typical of the Early Pleistocene. As summarized by Rook and Martinez Navarro (2010), the earlyemiddle Villafranchian mammal turnover, characterized by the dispersal in Europe of species adapted to open environments such as elephants and horses [the so-called “elephant-Equus event” of Lindsay et al., 1980; see also Azzaroli, 1977], took place broadly at this time. The use of the “elephant-Equus event” to mark the earlyemiddle Villafranchian turnover is however questioned by the
* Corresponding author. E-mail address: [email protected] (L. Bellucci). 1040-6182/$ e see front matter Ó 2011 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2011.04.006
recent finding of modern monodactyl horses and elephants (Mammuthus) in at least two early Villafranchian localities of Europe, i.e. in the Dacian Basin of Romania (Radulescu and Samson, 2001; Lister et al., 2005) and at Vialette in France (Lacombat et al., 2008). The fossiliferous sites of the Anagni basin (central Italy; Fig. 1) provide data of particular interest to elucidate the relationship between the “elephant-Equus event” and the earlyemiddle Villafranchian turnover. The sites of Coste San Giacomo, Fontana Acetosa (this latter also known as Acqua Acetosa), and Valle Catenaccio (Fig. 1) have been studied since the end of the 1970s by researchers of the Istituto Italiano di Paleontologia Umana (IsIPU) in Rome (Biddittu et al., 1979; Biddittu and Segre, 1982). The Coste San Giacomo site (CSG) was discovered during a survey carried out in 1978 along the Fosso delle Mole valley and its terraces (Fig. 2). In 1985, 1989, and 1990 trenches were excavated at the base of a terrace, finding a laterally traceable level with fossil vertebrates in the yellow sands thereby exposed. Correlative sandy/clayey deposits with fossil vertebrates were discovered in the same area at Valle Catenaccio (VC) and Fontana Acetosa (FA). Finally, in 2009 the IsIPU promoted the drilling of a 40 m-long core with the aim of investigating the depositional environment of this part of the Anagni basin and to provide a new chronology for the CSG fossil
L. Bellucci et al. / Quaternary International 267 (2012) 30e39
Mts
FA CSG VC
FR
. Sim
bruin
31
i ( Ern ici)
CM L. Canterno Anagni basin Plio-Pleistocene Plio-Plei i basins Reliefs > 500 m
Anagni
HOLOCENE–LATE HOLOCEN N PLEISTOCENE Colluvial, alluvial, “terra rossa”, upper travertine deposits MIDDLE PLEISTOCENE
Sac
nico ntela Mo
Pedogenized pyroclastics, lacustrine deposits and travertine Alban Hills pyroclastic flow and Ernici volcanics
Padun
R.
Gavignano
co
i
Ferentino
EARLY PLEISTOCENE (GELASIAN) P Marsh and fluvial deposits
R.
Villamagna
PLIOCENE PLIOCEN N Gavignano tectonic facies megaconglomerates Bedrock
Sgurgola
Late Miocene turbidites
Montelanico
Mts.
Sacco
Lepi
Morolo
ni (A
Middle Miocene marine epilitoral limestones Cretaceous to early Miocene platform limestones R.
Tectonics Thrusts
uson
i)
Faults
N 0
Sites CM - Colle Marino CSG - Coste San Giacomo FA - Fontana Acquacetosa FR - Fontana Ranuccio VC - Valle Catenaccio
km 2
Fig. 1. Geological map of the Anagni basin with the faunal sites discussed in text: Coste San Giacomo (CSG), Fontana Acetosa (FA), Fontana Ranuccio (FR), and Valle Catenaccio (VC).
assemblage. The core recovered a previously unknown stratigraphic succession, which is object of a multidisciplinary study including facies, ostracods, pollen, and palaeomagnetic analyses. In this paper, sedimentological and palaeontological data from the core are presented and discussed together with a preliminary reappraisal of the CSG faunal assemblage. CSG represents a crucial site to understand the palaeoenvironmental and faunal changes in Italy during the Early Pleistocene (Gelasian sensu Gibbard et al., 2010), just before the dispersal events that led into Europe African taxa such as, among others, Homo sp., Megantereon whitei, and Theropithecus sp. (O’Regan et al., in press). 2. Geological setting The Coste San Giacomo site is located close to Anagni, w50 km southeast of Rome (central Italy). The Anagni basin, covering an area of w20 km2, is a deeply faulted, extensional depression produced during the initial phases of the neotectonic evolution of the Apennines. The basin, bounded by horsts of Mesozoic to Miocene rocks (Segre and Ascenzi, 1984; Carrara et al., 1995; Ascenzi et al., 1996; Segre, 2004), largely developed between the Late Pliocene and the earlier part of the Middle Pleistocene (Carrara et al., 1995; Galadini and Messina, 2004), and was affected by regional volcanic activity of the Alban Hills, Ernici, and Roccamonfina volcanoes since w0.7 Ma (e.g. Giannetti, 2001; Peccerillo, 2005; Rouchon et al., 2008) (Fig. 1). To the southeast, the Anagni basin is bounded by the Sgurgola-Ferentino bedrock ridge (Alberti et al., 1975), which could have acted as a dam for lacustrine sedimentation during the Early Pleistocene (Muttoni et al., 2009) (Fig. 1). These lacustrine-alluvial sediments were covered by travertine (Segre and Ascenzi, 1984) and by Middle Pleistocene pyroclastics, dated at Fontana Ranuccio between 0.528 Ma and 0.487 Ma (KeAr dating, Biddittu et al., 1979) and attributed to the Alban Hills magmatic district (w0.7e0.02 Ma; Peccerillo, 2005).
3. The Coste San Giacomo 1 core The Coste San Giacomo 1 core (CSG1) was drilled in September 2009 at the site with coordinates N41450 21.700 E13 050 49.400 (WGS84 reference system), 206 m above sea level (Fig. 3). The core penetrated 40 m of sediments, but experienced an overall expansion of w10% during drilling operations, reaching a total thickness of 43.4 m. Depths reported in Fig. 3 have not been corrected for the expansion and reflect the actual measured length of the core. Core description and facies analysis were performed by taking into account sediment texture, structure, colour, weathering, vertical lithofacies variation, and the occurrence of accessory features such as roots, organic matter, wood fragments, fossils and bioturbation. Sand texture and colour were determined by means of a 0.5 4 sediment comparator (Udden-Wentworth grain-size classification scheme) and the Munsell Soil Color Chart, respectively. CaCO3 content was qualitatively evaluated in field with a w5% HCl solution, but no remarkable variations (e.g. depletion) were observed throughout the core. Core segments do not show any pervasive sediment disturbance (e.g. concave-downward warping or flowin structures), except for occasional fluidization of some sandy layers. Planar-parallel laminations in the sediment show a gentle tilt of w15e20 , perhaps produced by post-depositional tectonic activity. The palaeoenvironmental interpretation of the CSG1 core was carried out by integrating information from facies analysis and micropalaeontological content (ostracodes and charophytes). A total of 180 standard (w10 cm3) samples was taken every 20 cm throughout core. The samples have been disaggregated in 5% diluted hydrogen peroxide, wet-sieved through a 65 mm and 125 mm mesh and oven-dried. Ostracod valves and carapaces (1 individual ¼ 1 carapace or 1 valve) were identified under a stereoscopic binocular microscope and classified according to the taxonomical scheme of Meisch (2000). The derived auto-ecological preferences are listed in Table 1.
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Fig. 2. a) General overview of the CSG site (arrow corresponds to location of CSG section); b) the CSG section in 1990.
In the CSG1 core, 4 major facies associations (Fig. 3) pertaining to a continental environment mainly ascribable to an alluvial plain depositional system have been identified. 3.1. Marsh facies association 3.1.1. Description This facies association consists of a 20-m-thick vertical stack of laminated, fine-grained deposits with interbedded sand layers and organic-rich intervals (lignite and gyttja). The fine-grained deposits, mainly silty clay, are characterized by faint, cm-thick, planar-parallel lamination and display a dominant grey colour with bluish (5PB 5-6/1, 10B 4/1) to greenish (10G 4-5/1, 5GY 5-6/1) hues. Sand layers are usually normal-graded or massive and show a thinning-upward trend through all the facies association. Some inverse-graded sand layers are observed near the bottom of the facies association. Lignite and organic-rich intervals range in thickness from w0.5 to w2 m and seem to occur in a cyclical way through all the facies association. CaCO3 nodules are observed in very few layers. In addition to wood fragments and vegetation remains, the fossil content includes freshwater ostracods and charophytes (Characeae gyrogonites). Ostracods have been recovered from several intervals within this facies association (Fig. 3). In samples from assemblages A and B (Fig. 3), respectively at 27.85e27.80 m and 25.10e25.05 m, only juvenile forms of Candona sp. juv. occur (Fig. 4f). The sample at 19.30e19.15 m (Fig. 3, assemblage C) bears the richest and most diversified fauna of the core, with Ilyocypris gibba (Fig. 4a), Herpetocypris reptans, Potamocypris zschokkei, Candona candida, and juvenile forms of noded
Cyprideis torosa. At 18.60e18.55 m, (Fig. 3, assemblage D) two species of Mixtacandona and Potamocypris sp. juvenile forms are observed. Finally, in the assemblage E (17.95e17.60 m; Fig. 3) Cyclocypris ovum and fragments of Candonidae and H. reptans are documented together with gyrogonites of the Characee group. This facies association is observed in the core interval 39.60e17.60 m (Fig. 3). 3.1.2. Interpretation The occurrence of laminated, fine-grained deposits points to settling as main depositional process. The vertical thickness of this facies association suggests a long-standing water body, where the cyclic occurrence of vegetal remains and organic-rich intervals may reflects variations in the water depth. The bluish to greyish hues are characteristic of oxygen depletion and waterlogged conditions but, however, the preservation of primary sedimentary features (e.g. lamination) and the lack of mottling rule out remarkable pedogenic processes. The occurrence of rare layers with CaCO3 nodules may be ascribed to groundwater level oscillations. Moving throughout the facies association, the ostracod assemblages depict slightly different environmental conditions, mainly in the uppermost part of the facies association. Juvenile forms of Candona sp. juv. (Fig. 3, assemblages A and B) suggest a stressed environment, while the assemblage with I. gibba, H. reptans, P. zschokkei, and C. candida (Fig. 3, assemblage C) is typical of shallow, slowly flowing water with a clayey substrate. Juvenile forms of noded C. torosa indicate a slight salinity in the water body. The occurrence of Mixtacandona (Fig. 3, assemblage D) points to the vent of interstitial waters (Rogulj et al., 1994), while the Potamocypris sp. juvenile forms are common in
L. Bellucci et al. / Quaternary International 267 (2012) 30e39
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Fig. 3. The Coste San Giacomo 1 core. From left to the right: facies association, lithology, sedimentary features, and ostracod associations. On the right, the location of the core site and the physical correlation of CSG1 core with the CGS faunal site are shown. The area and the level where the CSG fauna was collected are displayed in grey. Bones recovered in the CSG1 core at the depth interval of 4.90e5.10 m have the same elevation as the CSG fauna. FR1 and FR2 are respectively the Fontana Ranuccio 1 and Fontana Ranuccio 2 cores (Segre Naldini et al., 2009; Muttoni et al., 2009).
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L. Bellucci et al. / Quaternary International 267 (2012) 30e39
Table 1 Auto-ecological preferences of the determined ostracod species (from Meisch, 2000 and Frenzel et al., 2010). Candona sp. juv., Potamocypris sp. and Pseudocandona sp. juv. are not included in the list. Taxon
Salinity
Temperature
Habitat
Substrate
Candona candida Candonopsis kingslei Cyclocypris ovum Cyprideis torosa Herpetocypris reptans Ilyocypris gibba Mixtacandona laisi Mixtacandona tabacauri Potamocypris zschokkei Pseudocandona eremita Pseudocandona rostrata
Freshwater to aeoligohaline Freshwater to aeoligohaline Freshwater to aeoligohaline Holeuryhaline Freshwater to beoligohaline Freshwater to aeoligohaline Freshwater Freshwater Freshwater Freshwater Freshwater
Oligothermophilic Thermoeuryplastic Thermoeuryplastic Polythermophylic Thermoeuryplastic Meso-polythermophilic
Endobenthic Endobenthic Nectobenthic Endoeepibenthic Endoeepibenthic phytal Nectobenthic Hyporheic Hyporheic Stygophilic Stygobitic Stygophilic
Sediment Mud Sediment Sediment (mud) Mud Sediment
Cold stenothermal Cold stenothermal
slowly flowing streams. C. ovum together with fragments of Candonidae and H. reptans (Fig. 3, assemblage E) suggests a permanent water body with muddy floor and rich vegetation. H. reptans is known to feed preferably on old Chara (macroalgae) (Meisch, 2000) and gyrogonites of the Characee group have been found in association with H. reptans. Gyrogonites also indicate a permanent water body with clear, shallow waters. Auto-ecological data suggest
Fine mud
standing to slowly flowing, shallow-water conditions and record also episodes of low salinity in the order of w5& of NaCl. Low salinity episodes can be ascribed to a negative hydrologic balance in closed basin settings, where water flows in during floods and is removed by evaporation (e.g. Langbein, 1961; Anadón et al., 1994). As a whole, this facies association is interpreted as a marsh, likely related to an aggrading floodplain.
Fig. 4. Most common ostracod taxa recovered from the CSG sediment core. Scale bars ¼ 200 mm, except otherwise stated. a) Ilyocypris gibba (Ramdohr, 1808), RV, sample 19.30e19.25; b) Pseudocandona sp. juv., sample 5.55e5.50; c) Mixtacandona laisi (Klie, 1938), LV, sample 15.00e15.05, scale bar ¼ 100 mm; d) Pseudocandona eremita (Veidovsky, 1882), LV, sample 15.00e15.05; e) Candonopsis kingslei (Brady and Robertson, 1870), carapace, sample 15.00e15.05; f) Candona sp. juv., sample 27.85e27.80, scale bar ¼ 100 mm.
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3.2. Near-shore facies association 3.2.1. Description This association is w5-m-thick and consists of calcareous medium- to coarse-grained sand and silt, massive or locally arranged in fining-upward cycles, with embedded siliciclastic silty clay or silty sand and organic-rich layers. The silty matrix in sand layers is generally abundant, but the original content could have been strongly influenced by fluidization during drilling. Cementation occurs only in few horizons and it is weak and sparse. Colour is mainly white (2.5Y 8/1, 5Y 8/1, 5PB 8/1), ranging from more oxidized (10YR 5/4, 2.5Y 6/6) to more reduced conditions (5G 6/1, 10GY, 5PB 6/1, 5Y 4-6/3). This facies association provided to be largely barren, except at interval 15.90e13.40 m (Fig. 3, assemblage F) where Mixtacandona laisi (Fig. 4c,d), Mixtacandona tabacauri, Candonopsis kingslei (Fig. 4e), and Pseudocandona eremita (Fig. 4d) were observed. This facies association is observed from the core’s bottom to 39.60 m and in the interval 17.60e12.70 m (Fig. 3). 3.2.2. Interpretation The interpretation of this facies association is not straightforward, as its sediments experienced strong fluidization and partial recovery during drilling operations. The texture of calcareous sediments and the occurrence of organic matter may reflect a context of shallow-water conditions, with large biochemical production of calcareous concretions and organic matter from shore vegetation (e.g. Magny, 1992; Gierlowski-Kordesch, 1998). Medium- to coarse-grained sizes can be ascribed to high-energy wave dynamics (Magny, 1992) or, more likely, to postdepositional mechanical weathering produced by root action and alternating dry (subaerial exposure)/waterlogged conditions (Gierlowski-Kordesch, 1998 and references therein). Colour variations in the facies association may support this interpretation, as point to the presence of iron in both oxidized and reduced status due to periodical waterlogging (Retallack, 2001). Local finingupward trends may represent gradual transgressive events due to the water level rise. The ostracod assemblage is typical of interstitial habitat and could point to the proximity of a spring (DoleOlivier et al., 1993; Mößlacher et al., 1996). The occurrence of C. kingslei (partly epigean form) together with hypogean forms indicates mixed communities, which must move with hydrological variations, being unable to survive desiccation. Taking into account the aforementioned features and the vertical relationship with the other facies associations (sections 3.1 and 3.3), this facies association is interpreted as a near-shore environment of a still-water body (marsh). 3.3. Floodplain facies association 3.3.1. Description Dominant fine-grained, laminated sediments with few inversegraded or massive sand layers compose this facies association, together with accessory features such as CaCO3 nodules, rootlets, and very small fragments of organic material. Lamination and CaCO3 nodules are frequent throughout the facies association. Colour mainly ranges from greenish/bluish grey (10BG 5/1, 10Y 5/1, 10B 6/1, 10G 4/1) and olive (5Y 6/3, 2.5Y 6/8), with few layers having more yellowish hues (2.5Y 7/4, 2.5Y 6/3). Upward, in a virtual coarsening trend, the succession pass to normal-graded, mediumto fine-grained, thin-bedded silty sand, locally arranged into sand to silt fining-upward sequences, with sharp base and CaCO3 nodules in the silt layer. Ostracods have been recovered in the upper part of the facies association. The assemblage is made up of Pseudocandona rostrata with subordinate Candonopsis juv. in the
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assemblage G (Fig. 3) and Pseudocandona sp. juv. (Fig. 4b), Candona sp. juv., Mixtacandona juv. in the assemblage H (Fig. 3). At the whole, this facies association is observed from 12.70 to 5.10 m (Fig. 3). 3.3.2. Interpretation The occurrence of fine-grained, laminated deposits point to settling as main depositional process, while the few sand layers reflects short-lived, moderate-energy events. CaCO3 nodules, rootlets, and the organic material mark alternating phases of waterlogging and subaerial exposure. All these features point to a floodplain deposit. This interpretation is supported by the occurrence of P. rostrata (Fig. 3, assemblage G), a cold stenothermal species, rheotolerant and stygophilic, which lives in both permanent and temporary small water bodies. Upward, the thin alternation of normal-graded sand and silt reflects a change in sedimentation style, with an increase of short-lived, moderateenergy events, tentatively ascribable to a crevasse splay (6.55e5.10 m; Fig. 3). The occurrence of Pseudocandona sp. juv., Candona sp. juv., and Mixtacandona juv. (Fig. 3, assemblage H) still indicates a temporary water body influenced by interstitial waters. 3.4. Fluvial-channel facies association 3.4.1. Description This facies association is w5-m-thick and consists of a vertical stack of amalgamated, moderately sorted, normal-graded, finegrained sands. Sedimentary structures include massive sand layers, as well as ripple cross-lamination and horizontal planar bedding. The sand stack has a lower erosional boundary and displays a fining-upward trend, gradually evolving into massive or locally laminated clayey silt with CaCO3 nodules and rootlets. Colour typically ranges from yellow to olive hues (2.5Y 7/3, 5Y 6/3). This facies association is barren of ostracods, but several vertebrate fragments were observed at 5.10e4.90 m, resting onto the erosional surface. This facies association occurs at the top of the core, from 5.10 to 0.60 m (Fig. 3). 3.4.2. Interpretation The general fining-upward trend, together with the occurrence of traction structures, erosional surfaces, and reworked fragments of accessory features (in this case, bones) are characteristic of a fluvial-channel deposit (e.g. Miall, 2006). The gradual upward transition to fine-grained deposits is interpreted as channel abandonment, with sedimentary processes changing from traction to mainly settling. The occurrence of CaCO3 nodules and rootlets at the top of the facies association points to subaerial exposure and weak weathering. 4. Mammal fauna Biddittu et al. (1979) described the palaeontological sites of the Anagni basin and remarked on the occurrence of Villafranchian mammal assemblages at Coste San Giacomo (CSG), Valle Catenaccio (VC), and Fontana Acetosa (FA) (Fig. 1). The species reported from FA are Mammuthus meridionalis, Hippopotamus sp., Stephanorhinus etruscus, Leptobos sp., Sus strozzi, Equus stenonis, Eucladoceros sp., “Cervus philisi”, Megantereon cultridens, Pachycrocuta sp., Canis sp., Lepus sp., and Testudo sp. Only a few vertebrate remains have been found in the yellow sands at VC, namely Mammuthus sp., E. stenonis, Eucladoceros sp., Gazella borbonica, Pachycrocuta sp., Castor fiber, Testudo sp., and Emys sp. (Cassoli and Segre Naldini, 1984, 1993; Segre Naldini and Valli, 2004).
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A larger amount of fossils comes from the CSG site. Fossil bones were collected from ground surface, where the fossil-bearing yellow sands are ploughed for agriculture. The surveys provided diversified faunal assemblages that Biddittu et al. (1979) referred to the middle Villafranchian because of the affinities of CSG fauna with that from Saint Vallier (France) (Viret, 1954; Guérin et al., 2004, and references therein). In recent times an increasing number of localities with middle Villafranchian faunas has been discovered and studied (Varshets in Bulgaria; Sesklo, Dafnero, Vatera, Volakas in Greece; Rook and Martinez Navarro, 2010, with references therein). Gliozzi et al. (1997) pointed out and updated the biochronology for
PlioePleistocene mammals of Italy and defined the Costa San Giacomo Faunal Unit (FU). As Rook and Martinez Navarro (2010) summarized, the faunal composition of middle Villafranchian units is characterized by some important first occurrences, including those of S. etruscus, E. stenonis, Sus cf. strozzii, the rupicaprine Gallogoral meneghinii, and the spiral horned antelope Gazellospira torticornis. In addition, the first occurrence of Canis cf. C. etruscus, a carnivore very common in the later faunal units, has particular biochronological relevance. The occurrence of Canis cf. C. etruscus in the CSG fauna (Rook and Torre, 1996) suggested that the so-called “Wolf-event” of Azzaroli (1983) started earlier than originally assumed and cannot indicate the
Fig. 5. Selected fossil remains from the CSG site. a) Mammuthus meridionalis; b) Anancus arvernensis; c) Gazellospira torticornis; d) Gazella borbonica; e) Equus stenonis; f) Hippopotamus sp. Scale bar ¼ 10 mm.
L. Bellucci et al. / Quaternary International 267 (2012) 30e39
PlioePleistocene transition (Palombo and Sardella, 2007). Finally, recent identification of Canis sp. in the early Villafranchian of Vialette, indicates that the diffusion of wolf-like dogs across Eurasia was a diachronous event (Lacombat et al., 2008; Sotnikova and Rook, 2010). Besides the First Appearance Datum (FAD) of Canis cf. C. etruscus, the CSG faunal assemblage shows other peculiar features of biochronological value such as the occurrence of gazelle and antelopes (G. borbonica and G. torticornis), coexistence of Anancus arvernensis and M. meridionalis, and the Last Appearance Datum (LAD) of A. arvernensis. Summarizing, the CSG faunal assemblage is definitely middle Villafranchian and characterized by the following taxa: Macaca cf. M. sylvanus florentina COCCHI, A. arvernensis (CROIZET AND JOBERT), M. meridionalis NESTI, Stephanorhinus sp. KRETZOI, E. stenonis COCCHI, Axis lyra (¼ C. philisi SCHAUB), Eucladoceros cf. E. teguliensis (DUBOIS), Croizetoceros ramosus HEINTZ, Cervidae indet., Leptobos sp., G. borbonica DEPÉRET, G. torticornis (AYMARD), Gazella sp., Canis cf. C. etruscus FALCONER, Vulpes cf. V. alopecoides MAJOR, Hyaenidae (possibly Chasmaporthetes HAY), Homotherium sp. and Hystrix cf. H. refossa GERVAIS, Talpa sp. LINNAEUS (Figs. 5 and 6). During the survey attending the drilling activity some new mammal fossil remains were found in the field where most of the CSG FU bones were previously collected. Among them, an upper incisor referable to Hippopotamus sp. (Fig. 5f) is of particular interest and adds a new element to the faunal list. The occurrence of the hippo in late Villafranchian faunal assemblages (Olivola and Tasso FUs; Gliozzi et al., 1997) has been recently questioned and the earliest presence of the taxon in Europe was then considered that from Venta Micena (Spain), correlative to the Pirro Nord FU in Italy (Rook and Martinez Navarro, 2010, with references therein). The FA faunal assemblage was previously considered late Villafranchian in age due to the occurrence of Hippopotamus remains (teeth and fragments of limb bones). Thus the FA fossils were considered slightly younger than CSG, despite the fact that correlation between the fossiliferous levels of CSG and the FA could be supported by field evidence. The new finding of Hippopotamus in CSG allows to refer also the FA assemblage to the middle Villafranchian. Therefore the occurrence of Hippopotamus, reported both in CSG and FA assemblages, assume a remarkable
Fig. 6. Selected fossil remains from the CSG site. a) Chasmaporthetes; b) Canis cf. C. etruscus; c) Homotherium sp.; d) Macaca cf. M. sylvanus florentina. Scale bar ¼ 10 mm.
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biochronological value. In addition, Reimann and Strauch (2008) reported the occurrence of a partial skull of hippo in a middle Villafranchian faunal assemblage from Elis (Peloponnesus, Greece), albeit these authors did not provide a faunal list. Finally, the tooth from CSG confirms the presence of the hippo in the middle Villafranchian in the Italian peninsula, thus demonstrating the diffusion into Europe of an African taxon. Therefore, the dispersal event of the hippo occurred earlier than previously supposed, pre-dating the dispersal of other African taxa during the Early Pleistocene. 5. Discussion The integration of facies analysis and palaeoecological information provided by ostracods and mammal fauna led to the palaeoenvironmental reconstruction of the CSG site. The vertical distribution of facies and ostracod associations points to an aggrading, low-energy environment, with slowly flowing, cold, shallow waters, largely ascribable to an alluvial plain. The w20-mthick marshy succession suggests a long-standing, depressed area of an alluvial plain, probably confined by the bedrock. The bedrock is presently exposed few hundreds meters far from the CSG1 site (Fig. 1) and, in a context of regional aggradation, the marshy depression could be originated by fluvial damming of a recess or a small tributary valley cut into the bedrock. This kind of marshy environment is marginal to the alluvial plain and is largely documented at the foot of the Southern Alps (Ravazzi et al., 2005; Scardia et al., 2010) and the Berici-Euganean hills (e.g. Calderoni et al., 1996; Kaltenrieder et al., 2009; Monegato et al., in press). The marsh at CSG likely developed as a closed basin, where water inflow mainly occurred during floods and was removed by evaporation. Large amounts of organic matter and lignite suggest general humid conditions, during which floods regularly provided water to the marsh and vegetation proliferated along the margin. Episodic negative balance between water inflow and evaporation may have led to moderate salinity increase as documented by the occurrence of noded specimens of C. torosa (Vesper, 1972). Evolution in time led the marsh to be completely filled and to evolve into a low-energy floodplain, with episodic floods and more frequent subaerial exposure. The last facies association in the CSG1 core registers the approach of a sand-bed fluvial-channel, at the base of which bones lie as a lag. Although taphonomic analyses have not been performed yet, bones fragments recovered in the fluvial-channel deposits would suggest a reworking by the water flow for the CSG faunal assemblage. The CSG1 succession ends with the gradual abandonment of the fluvial-channel. A peculiarity of the ostracod assemblage is the concomitant occurrence of epibenthic and hyporheic to stygobitic species in the assemblages D, F, G, and H (Fig. 3). Typically, these species occur in interstitial and groundwater habitats, springs and waters connected to springs, and some of them in a broad range of different freshwater ecosystems. The groundwater hosted in the Mesozoic to Miocene rocks forming the backbones of the Anagni basin (Fig. 1) potentially represents a specific habitat for such taxa and their occurrence in assemblages D and F (Fig. 3) may support the interpretation of a marshy depression confined between the bedrock and an aggrading alluvial plain. The occurrence of Mixtacandona juv. in floodplain settings (Fig. 3, assemblage H) could also be linked to local groundwater characteristics, to the existence of floodplain springs and to the peculiar position of the water body within the floodplain (Ward et al., 1998). Danielopol et al. (1997) studying the interstitial fauna in the Danube Valley near Vienna, reported rich ostracod assemblages during spring and poor assemblages during summer and autumn, corresponding respectively to well oxygenated and hypoxic or anoxic sediment conditions.
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L. Bellucci et al. / Quaternary International 267 (2012) 30e39
Ascenzi (1993) reported Candona albicans from fine-grained deposits exposed along the rivers’ banks in the study area, but the age of these deposits seems presently to be younger than CSG, because of the different topographic elevation and the available palaeomagnetic constrains (Muttoni et al., 2009). The occurrence of hippos agrees with flowing and/or clear waters, as well as with the presence of plants and grasses. Hippos probably lived in the alluvial plain, which was an important water source for many species, while the occurrence of canids, hyaenids, large equids, and gazelles suggests the presence in the area of prairies and grasslands. Such a scenario can be supported also by the occurrence of M. meridionalis with a molar teeth pattern adapted to grazing grass and other types of hard vegetation. As suggested by different authors (Palmqvist et al., 2003; Russo Ermolli et al., 2010), the living African hippo and also the Pleistocene Hippopotamus antiquus cannot be considered tout court as indicators of warm climate conditions, but its occurrence is suitable to mild conditions. At present, only general palaeoenvironmental considerations can be provided by the vertebrate fossil record from CSG.
6. Conclusions Recent drilling and field activities at the CSG faunal site provided a new stratigraphic data and fossil bones. The CSG1 core, drilled few meters above the local base-level to a depth of 40 m, allowed to recover a previously unknown sedimentary succession. The vertebrate-bearing level, known previously from surface exposure, was detected in the CSG1 core at 5.10e4.90 m below the ground level. The integration of facies analyses, micro- and macropalaeontological observations has led to a more detailed interpretation of the palaeoenvironmental settings of the CSG area in the very early Pleistocene, largely pointing to a low-energy alluvial plain with prairies and grasslands, fed by sand-bed rivers. Among the new findings, an upper incisor of Hippopotamus was collected in the field. This record has a valuable biochronological importance, and it enables pre-dating the occurrence of this taxon to an earlier moment of the Early Pleistocene, witnessing a dispersal event from Africa into Europe more than 2 Ma ago. Palaeomagnetic and palaeobotanical analyses are in progress in order to provide a more complete scenario with firm chronologic constraints.
Acknowledgments We wish to thank Annalisa Zarattini (Soprintendenza per i Beni Archeologici del Lazio) who authorized ongoing field activity, Pierluigi Friello for the technical assistance during the drilling work, the Micropalaeontological Laboratory at Roma Tre University for providing access to their facilities, and Sergio Lo Mastro (Roma Tre University) for the SEM pictures. Italu Biddittu, Laura Bruni, Amalia Faraci, and Barbara Saracino helped during the different steps of the research. Mauro Cremaschi, Massimiliano Ghinassi, Giovanni Monegato, and Giovanni Muttoni are thanked for the useful comments and discussions on the early versions of the manuscript. We want also to thank Roberto Chiararia, Director of “Convitto Nazionale Regina Margherita” of Anagni, for providing assistance and facilities. Research was financially supported by Banca di Credito Cooperativo Anagni, by MIUR Grants “Ricerca di Ateneo federato di Scienze e Tecnologia AST Sapienza 2007” (Project: “I mammiferi del Pleistocene Inferiore italiano: evoluzione, migrazioni, biocronologia”; Resp.: R. Sardella), by MIUR IsIPU “funding 2008e2010”.
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The site of Coste San Giacomo (Early Pleistocene, central Italy): Palaeoenvironmental analysis and biochronological overview Luca Bellucci a, *, Ilaria Mazzini b, Giancarlo Scardia c, Luciano Bruni a, Fabio Parenti a, Aldo Giacomo Segre a, Eugenia Segre Naldini a, Raffaele Sardella d a
Istituto Italiano di Paleontologia Umana, Piazza Mincio 2, I-00198 Roma, Italy IGAG-CNR, Via Salaria Km 29.3, CP 10, Monterotondo Staz., I-00016 Roma, Italy INGV, Sezione di Milano-Pavia, via Bassini 15, I-20133 Milano, Italy d Dipartimento di Scienze della Terra, “Sapienza” e Università di Roma, P.le Aldo Moro 5, I-00185 Roma, Italy b c
a r t i c l e i n f o
a b s t r a c t
Article history: Available online 15 April 2011
Facies and ostracod analyses have been performed on a continental core drilled at Coste San Giacomo (Anagni, central Italy), where a middle Villafranchian faunal assemblage was first discovered in 1978. The core intercepted the palaeontological level and penetrated the underlying sedimentary succession, previously largely unknown, for a total sediment recovery of 40 m. In addition, new field surveys led to the discovery of Hippopotamus sp. remains at the faunal site, thus pre-dating the dispersal of this large ungulate into Europe to the middle Villafranchian. The new sedimentological and palaeoecological data allowed to define a palaeoenvironment mainly ascribable to an alluvial plain, characterized by a marsh evolving into a floodplain with overbank deposits and a sand-bed fluvial-channel. This scenario is supported by the reassessed Coste San Giacomo faunal assemblage, consistent with running and/or clear waters as well as prairies and grasslands, under mild climatic conditions. Ó 2011 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction The PlioceneePleistocene (PiacenzianeGelasian) boundary, constrained at 2.588 Ma (Rio et al., 1994; Gibbard et al., 2010) and approximated by the GausseMatuyama polarity reversal (2.581 Ma; Lourens et al., 2005), straddles a global cooling trend between marine isotope stage (MIS) G2 to 100 (Lisiecki and Raymo, 2005) and culminating with the onset of obliquity-driven glacial/ interglacial cycles typical of the Early Pleistocene (Shackleton, 1995). This global cooling trend is temporally associated with the demise of Pliocene ecosystems and the spread of fauna and flora associations typical of the Early Pleistocene. As summarized by Rook and Martinez Navarro (2010), the earlyemiddle Villafranchian mammal turnover, characterized by the dispersal in Europe of species adapted to open environments such as elephants and horses [the so-called “elephant-Equus event” of Lindsay et al., 1980; see also Azzaroli, 1977], took place broadly at this time. The use of the “elephant-Equus event” to mark the earlyemiddle Villafranchian turnover is however questioned by the
* Corresponding author. E-mail address: [email protected] (L. Bellucci). 1040-6182/$ e see front matter Ó 2011 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2011.04.006
recent finding of modern monodactyl horses and elephants (Mammuthus) in at least two early Villafranchian localities of Europe, i.e. in the Dacian Basin of Romania (Radulescu and Samson, 2001; Lister et al., 2005) and at Vialette in France (Lacombat et al., 2008). The fossiliferous sites of the Anagni basin (central Italy; Fig. 1) provide data of particular interest to elucidate the relationship between the “elephant-Equus event” and the earlyemiddle Villafranchian turnover. The sites of Coste San Giacomo, Fontana Acetosa (this latter also known as Acqua Acetosa), and Valle Catenaccio (Fig. 1) have been studied since the end of the 1970s by researchers of the Istituto Italiano di Paleontologia Umana (IsIPU) in Rome (Biddittu et al., 1979; Biddittu and Segre, 1982). The Coste San Giacomo site (CSG) was discovered during a survey carried out in 1978 along the Fosso delle Mole valley and its terraces (Fig. 2). In 1985, 1989, and 1990 trenches were excavated at the base of a terrace, finding a laterally traceable level with fossil vertebrates in the yellow sands thereby exposed. Correlative sandy/clayey deposits with fossil vertebrates were discovered in the same area at Valle Catenaccio (VC) and Fontana Acetosa (FA). Finally, in 2009 the IsIPU promoted the drilling of a 40 m-long core with the aim of investigating the depositional environment of this part of the Anagni basin and to provide a new chronology for the CSG fossil
L. Bellucci et al. / Quaternary International 267 (2012) 30e39
Mts
FA CSG VC
FR
. Sim
bruin
31
i ( Ern ici)
CM L. Canterno Anagni basin Plio-Pleistocene Plio-Plei i basins Reliefs > 500 m
Anagni
HOLOCENE–LATE HOLOCEN N PLEISTOCENE Colluvial, alluvial, “terra rossa”, upper travertine deposits MIDDLE PLEISTOCENE
Sac
nico ntela Mo
Pedogenized pyroclastics, lacustrine deposits and travertine Alban Hills pyroclastic flow and Ernici volcanics
Padun
R.
Gavignano
co
i
Ferentino
EARLY PLEISTOCENE (GELASIAN) P Marsh and fluvial deposits
R.
Villamagna
PLIOCENE PLIOCEN N Gavignano tectonic facies megaconglomerates Bedrock
Sgurgola
Late Miocene turbidites
Montelanico
Mts.
Sacco
Lepi
Morolo
ni (A
Middle Miocene marine epilitoral limestones Cretaceous to early Miocene platform limestones R.
Tectonics Thrusts
uson
i)
Faults
N 0
Sites CM - Colle Marino CSG - Coste San Giacomo FA - Fontana Acquacetosa FR - Fontana Ranuccio VC - Valle Catenaccio
km 2
Fig. 1. Geological map of the Anagni basin with the faunal sites discussed in text: Coste San Giacomo (CSG), Fontana Acetosa (FA), Fontana Ranuccio (FR), and Valle Catenaccio (VC).
assemblage. The core recovered a previously unknown stratigraphic succession, which is object of a multidisciplinary study including facies, ostracods, pollen, and palaeomagnetic analyses. In this paper, sedimentological and palaeontological data from the core are presented and discussed together with a preliminary reappraisal of the CSG faunal assemblage. CSG represents a crucial site to understand the palaeoenvironmental and faunal changes in Italy during the Early Pleistocene (Gelasian sensu Gibbard et al., 2010), just before the dispersal events that led into Europe African taxa such as, among others, Homo sp., Megantereon whitei, and Theropithecus sp. (O’Regan et al., in press). 2. Geological setting The Coste San Giacomo site is located close to Anagni, w50 km southeast of Rome (central Italy). The Anagni basin, covering an area of w20 km2, is a deeply faulted, extensional depression produced during the initial phases of the neotectonic evolution of the Apennines. The basin, bounded by horsts of Mesozoic to Miocene rocks (Segre and Ascenzi, 1984; Carrara et al., 1995; Ascenzi et al., 1996; Segre, 2004), largely developed between the Late Pliocene and the earlier part of the Middle Pleistocene (Carrara et al., 1995; Galadini and Messina, 2004), and was affected by regional volcanic activity of the Alban Hills, Ernici, and Roccamonfina volcanoes since w0.7 Ma (e.g. Giannetti, 2001; Peccerillo, 2005; Rouchon et al., 2008) (Fig. 1). To the southeast, the Anagni basin is bounded by the Sgurgola-Ferentino bedrock ridge (Alberti et al., 1975), which could have acted as a dam for lacustrine sedimentation during the Early Pleistocene (Muttoni et al., 2009) (Fig. 1). These lacustrine-alluvial sediments were covered by travertine (Segre and Ascenzi, 1984) and by Middle Pleistocene pyroclastics, dated at Fontana Ranuccio between 0.528 Ma and 0.487 Ma (KeAr dating, Biddittu et al., 1979) and attributed to the Alban Hills magmatic district (w0.7e0.02 Ma; Peccerillo, 2005).
3. The Coste San Giacomo 1 core The Coste San Giacomo 1 core (CSG1) was drilled in September 2009 at the site with coordinates N41450 21.700 E13 050 49.400 (WGS84 reference system), 206 m above sea level (Fig. 3). The core penetrated 40 m of sediments, but experienced an overall expansion of w10% during drilling operations, reaching a total thickness of 43.4 m. Depths reported in Fig. 3 have not been corrected for the expansion and reflect the actual measured length of the core. Core description and facies analysis were performed by taking into account sediment texture, structure, colour, weathering, vertical lithofacies variation, and the occurrence of accessory features such as roots, organic matter, wood fragments, fossils and bioturbation. Sand texture and colour were determined by means of a 0.5 4 sediment comparator (Udden-Wentworth grain-size classification scheme) and the Munsell Soil Color Chart, respectively. CaCO3 content was qualitatively evaluated in field with a w5% HCl solution, but no remarkable variations (e.g. depletion) were observed throughout the core. Core segments do not show any pervasive sediment disturbance (e.g. concave-downward warping or flowin structures), except for occasional fluidization of some sandy layers. Planar-parallel laminations in the sediment show a gentle tilt of w15e20 , perhaps produced by post-depositional tectonic activity. The palaeoenvironmental interpretation of the CSG1 core was carried out by integrating information from facies analysis and micropalaeontological content (ostracodes and charophytes). A total of 180 standard (w10 cm3) samples was taken every 20 cm throughout core. The samples have been disaggregated in 5% diluted hydrogen peroxide, wet-sieved through a 65 mm and 125 mm mesh and oven-dried. Ostracod valves and carapaces (1 individual ¼ 1 carapace or 1 valve) were identified under a stereoscopic binocular microscope and classified according to the taxonomical scheme of Meisch (2000). The derived auto-ecological preferences are listed in Table 1.
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Fig. 2. a) General overview of the CSG site (arrow corresponds to location of CSG section); b) the CSG section in 1990.
In the CSG1 core, 4 major facies associations (Fig. 3) pertaining to a continental environment mainly ascribable to an alluvial plain depositional system have been identified. 3.1. Marsh facies association 3.1.1. Description This facies association consists of a 20-m-thick vertical stack of laminated, fine-grained deposits with interbedded sand layers and organic-rich intervals (lignite and gyttja). The fine-grained deposits, mainly silty clay, are characterized by faint, cm-thick, planar-parallel lamination and display a dominant grey colour with bluish (5PB 5-6/1, 10B 4/1) to greenish (10G 4-5/1, 5GY 5-6/1) hues. Sand layers are usually normal-graded or massive and show a thinning-upward trend through all the facies association. Some inverse-graded sand layers are observed near the bottom of the facies association. Lignite and organic-rich intervals range in thickness from w0.5 to w2 m and seem to occur in a cyclical way through all the facies association. CaCO3 nodules are observed in very few layers. In addition to wood fragments and vegetation remains, the fossil content includes freshwater ostracods and charophytes (Characeae gyrogonites). Ostracods have been recovered from several intervals within this facies association (Fig. 3). In samples from assemblages A and B (Fig. 3), respectively at 27.85e27.80 m and 25.10e25.05 m, only juvenile forms of Candona sp. juv. occur (Fig. 4f). The sample at 19.30e19.15 m (Fig. 3, assemblage C) bears the richest and most diversified fauna of the core, with Ilyocypris gibba (Fig. 4a), Herpetocypris reptans, Potamocypris zschokkei, Candona candida, and juvenile forms of noded
Cyprideis torosa. At 18.60e18.55 m, (Fig. 3, assemblage D) two species of Mixtacandona and Potamocypris sp. juvenile forms are observed. Finally, in the assemblage E (17.95e17.60 m; Fig. 3) Cyclocypris ovum and fragments of Candonidae and H. reptans are documented together with gyrogonites of the Characee group. This facies association is observed in the core interval 39.60e17.60 m (Fig. 3). 3.1.2. Interpretation The occurrence of laminated, fine-grained deposits points to settling as main depositional process. The vertical thickness of this facies association suggests a long-standing water body, where the cyclic occurrence of vegetal remains and organic-rich intervals may reflects variations in the water depth. The bluish to greyish hues are characteristic of oxygen depletion and waterlogged conditions but, however, the preservation of primary sedimentary features (e.g. lamination) and the lack of mottling rule out remarkable pedogenic processes. The occurrence of rare layers with CaCO3 nodules may be ascribed to groundwater level oscillations. Moving throughout the facies association, the ostracod assemblages depict slightly different environmental conditions, mainly in the uppermost part of the facies association. Juvenile forms of Candona sp. juv. (Fig. 3, assemblages A and B) suggest a stressed environment, while the assemblage with I. gibba, H. reptans, P. zschokkei, and C. candida (Fig. 3, assemblage C) is typical of shallow, slowly flowing water with a clayey substrate. Juvenile forms of noded C. torosa indicate a slight salinity in the water body. The occurrence of Mixtacandona (Fig. 3, assemblage D) points to the vent of interstitial waters (Rogulj et al., 1994), while the Potamocypris sp. juvenile forms are common in
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Fig. 3. The Coste San Giacomo 1 core. From left to the right: facies association, lithology, sedimentary features, and ostracod associations. On the right, the location of the core site and the physical correlation of CSG1 core with the CGS faunal site are shown. The area and the level where the CSG fauna was collected are displayed in grey. Bones recovered in the CSG1 core at the depth interval of 4.90e5.10 m have the same elevation as the CSG fauna. FR1 and FR2 are respectively the Fontana Ranuccio 1 and Fontana Ranuccio 2 cores (Segre Naldini et al., 2009; Muttoni et al., 2009).
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Table 1 Auto-ecological preferences of the determined ostracod species (from Meisch, 2000 and Frenzel et al., 2010). Candona sp. juv., Potamocypris sp. and Pseudocandona sp. juv. are not included in the list. Taxon
Salinity
Temperature
Habitat
Substrate
Candona candida Candonopsis kingslei Cyclocypris ovum Cyprideis torosa Herpetocypris reptans Ilyocypris gibba Mixtacandona laisi Mixtacandona tabacauri Potamocypris zschokkei Pseudocandona eremita Pseudocandona rostrata
Freshwater to aeoligohaline Freshwater to aeoligohaline Freshwater to aeoligohaline Holeuryhaline Freshwater to beoligohaline Freshwater to aeoligohaline Freshwater Freshwater Freshwater Freshwater Freshwater
Oligothermophilic Thermoeuryplastic Thermoeuryplastic Polythermophylic Thermoeuryplastic Meso-polythermophilic
Endobenthic Endobenthic Nectobenthic Endoeepibenthic Endoeepibenthic phytal Nectobenthic Hyporheic Hyporheic Stygophilic Stygobitic Stygophilic
Sediment Mud Sediment Sediment (mud) Mud Sediment
Cold stenothermal Cold stenothermal
slowly flowing streams. C. ovum together with fragments of Candonidae and H. reptans (Fig. 3, assemblage E) suggests a permanent water body with muddy floor and rich vegetation. H. reptans is known to feed preferably on old Chara (macroalgae) (Meisch, 2000) and gyrogonites of the Characee group have been found in association with H. reptans. Gyrogonites also indicate a permanent water body with clear, shallow waters. Auto-ecological data suggest
Fine mud
standing to slowly flowing, shallow-water conditions and record also episodes of low salinity in the order of w5& of NaCl. Low salinity episodes can be ascribed to a negative hydrologic balance in closed basin settings, where water flows in during floods and is removed by evaporation (e.g. Langbein, 1961; Anadón et al., 1994). As a whole, this facies association is interpreted as a marsh, likely related to an aggrading floodplain.
Fig. 4. Most common ostracod taxa recovered from the CSG sediment core. Scale bars ¼ 200 mm, except otherwise stated. a) Ilyocypris gibba (Ramdohr, 1808), RV, sample 19.30e19.25; b) Pseudocandona sp. juv., sample 5.55e5.50; c) Mixtacandona laisi (Klie, 1938), LV, sample 15.00e15.05, scale bar ¼ 100 mm; d) Pseudocandona eremita (Veidovsky, 1882), LV, sample 15.00e15.05; e) Candonopsis kingslei (Brady and Robertson, 1870), carapace, sample 15.00e15.05; f) Candona sp. juv., sample 27.85e27.80, scale bar ¼ 100 mm.
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3.2. Near-shore facies association 3.2.1. Description This association is w5-m-thick and consists of calcareous medium- to coarse-grained sand and silt, massive or locally arranged in fining-upward cycles, with embedded siliciclastic silty clay or silty sand and organic-rich layers. The silty matrix in sand layers is generally abundant, but the original content could have been strongly influenced by fluidization during drilling. Cementation occurs only in few horizons and it is weak and sparse. Colour is mainly white (2.5Y 8/1, 5Y 8/1, 5PB 8/1), ranging from more oxidized (10YR 5/4, 2.5Y 6/6) to more reduced conditions (5G 6/1, 10GY, 5PB 6/1, 5Y 4-6/3). This facies association provided to be largely barren, except at interval 15.90e13.40 m (Fig. 3, assemblage F) where Mixtacandona laisi (Fig. 4c,d), Mixtacandona tabacauri, Candonopsis kingslei (Fig. 4e), and Pseudocandona eremita (Fig. 4d) were observed. This facies association is observed from the core’s bottom to 39.60 m and in the interval 17.60e12.70 m (Fig. 3). 3.2.2. Interpretation The interpretation of this facies association is not straightforward, as its sediments experienced strong fluidization and partial recovery during drilling operations. The texture of calcareous sediments and the occurrence of organic matter may reflect a context of shallow-water conditions, with large biochemical production of calcareous concretions and organic matter from shore vegetation (e.g. Magny, 1992; Gierlowski-Kordesch, 1998). Medium- to coarse-grained sizes can be ascribed to high-energy wave dynamics (Magny, 1992) or, more likely, to postdepositional mechanical weathering produced by root action and alternating dry (subaerial exposure)/waterlogged conditions (Gierlowski-Kordesch, 1998 and references therein). Colour variations in the facies association may support this interpretation, as point to the presence of iron in both oxidized and reduced status due to periodical waterlogging (Retallack, 2001). Local finingupward trends may represent gradual transgressive events due to the water level rise. The ostracod assemblage is typical of interstitial habitat and could point to the proximity of a spring (DoleOlivier et al., 1993; Mößlacher et al., 1996). The occurrence of C. kingslei (partly epigean form) together with hypogean forms indicates mixed communities, which must move with hydrological variations, being unable to survive desiccation. Taking into account the aforementioned features and the vertical relationship with the other facies associations (sections 3.1 and 3.3), this facies association is interpreted as a near-shore environment of a still-water body (marsh). 3.3. Floodplain facies association 3.3.1. Description Dominant fine-grained, laminated sediments with few inversegraded or massive sand layers compose this facies association, together with accessory features such as CaCO3 nodules, rootlets, and very small fragments of organic material. Lamination and CaCO3 nodules are frequent throughout the facies association. Colour mainly ranges from greenish/bluish grey (10BG 5/1, 10Y 5/1, 10B 6/1, 10G 4/1) and olive (5Y 6/3, 2.5Y 6/8), with few layers having more yellowish hues (2.5Y 7/4, 2.5Y 6/3). Upward, in a virtual coarsening trend, the succession pass to normal-graded, mediumto fine-grained, thin-bedded silty sand, locally arranged into sand to silt fining-upward sequences, with sharp base and CaCO3 nodules in the silt layer. Ostracods have been recovered in the upper part of the facies association. The assemblage is made up of Pseudocandona rostrata with subordinate Candonopsis juv. in the
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assemblage G (Fig. 3) and Pseudocandona sp. juv. (Fig. 4b), Candona sp. juv., Mixtacandona juv. in the assemblage H (Fig. 3). At the whole, this facies association is observed from 12.70 to 5.10 m (Fig. 3). 3.3.2. Interpretation The occurrence of fine-grained, laminated deposits point to settling as main depositional process, while the few sand layers reflects short-lived, moderate-energy events. CaCO3 nodules, rootlets, and the organic material mark alternating phases of waterlogging and subaerial exposure. All these features point to a floodplain deposit. This interpretation is supported by the occurrence of P. rostrata (Fig. 3, assemblage G), a cold stenothermal species, rheotolerant and stygophilic, which lives in both permanent and temporary small water bodies. Upward, the thin alternation of normal-graded sand and silt reflects a change in sedimentation style, with an increase of short-lived, moderateenergy events, tentatively ascribable to a crevasse splay (6.55e5.10 m; Fig. 3). The occurrence of Pseudocandona sp. juv., Candona sp. juv., and Mixtacandona juv. (Fig. 3, assemblage H) still indicates a temporary water body influenced by interstitial waters. 3.4. Fluvial-channel facies association 3.4.1. Description This facies association is w5-m-thick and consists of a vertical stack of amalgamated, moderately sorted, normal-graded, finegrained sands. Sedimentary structures include massive sand layers, as well as ripple cross-lamination and horizontal planar bedding. The sand stack has a lower erosional boundary and displays a fining-upward trend, gradually evolving into massive or locally laminated clayey silt with CaCO3 nodules and rootlets. Colour typically ranges from yellow to olive hues (2.5Y 7/3, 5Y 6/3). This facies association is barren of ostracods, but several vertebrate fragments were observed at 5.10e4.90 m, resting onto the erosional surface. This facies association occurs at the top of the core, from 5.10 to 0.60 m (Fig. 3). 3.4.2. Interpretation The general fining-upward trend, together with the occurrence of traction structures, erosional surfaces, and reworked fragments of accessory features (in this case, bones) are characteristic of a fluvial-channel deposit (e.g. Miall, 2006). The gradual upward transition to fine-grained deposits is interpreted as channel abandonment, with sedimentary processes changing from traction to mainly settling. The occurrence of CaCO3 nodules and rootlets at the top of the facies association points to subaerial exposure and weak weathering. 4. Mammal fauna Biddittu et al. (1979) described the palaeontological sites of the Anagni basin and remarked on the occurrence of Villafranchian mammal assemblages at Coste San Giacomo (CSG), Valle Catenaccio (VC), and Fontana Acetosa (FA) (Fig. 1). The species reported from FA are Mammuthus meridionalis, Hippopotamus sp., Stephanorhinus etruscus, Leptobos sp., Sus strozzi, Equus stenonis, Eucladoceros sp., “Cervus philisi”, Megantereon cultridens, Pachycrocuta sp., Canis sp., Lepus sp., and Testudo sp. Only a few vertebrate remains have been found in the yellow sands at VC, namely Mammuthus sp., E. stenonis, Eucladoceros sp., Gazella borbonica, Pachycrocuta sp., Castor fiber, Testudo sp., and Emys sp. (Cassoli and Segre Naldini, 1984, 1993; Segre Naldini and Valli, 2004).
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A larger amount of fossils comes from the CSG site. Fossil bones were collected from ground surface, where the fossil-bearing yellow sands are ploughed for agriculture. The surveys provided diversified faunal assemblages that Biddittu et al. (1979) referred to the middle Villafranchian because of the affinities of CSG fauna with that from Saint Vallier (France) (Viret, 1954; Guérin et al., 2004, and references therein). In recent times an increasing number of localities with middle Villafranchian faunas has been discovered and studied (Varshets in Bulgaria; Sesklo, Dafnero, Vatera, Volakas in Greece; Rook and Martinez Navarro, 2010, with references therein). Gliozzi et al. (1997) pointed out and updated the biochronology for
PlioePleistocene mammals of Italy and defined the Costa San Giacomo Faunal Unit (FU). As Rook and Martinez Navarro (2010) summarized, the faunal composition of middle Villafranchian units is characterized by some important first occurrences, including those of S. etruscus, E. stenonis, Sus cf. strozzii, the rupicaprine Gallogoral meneghinii, and the spiral horned antelope Gazellospira torticornis. In addition, the first occurrence of Canis cf. C. etruscus, a carnivore very common in the later faunal units, has particular biochronological relevance. The occurrence of Canis cf. C. etruscus in the CSG fauna (Rook and Torre, 1996) suggested that the so-called “Wolf-event” of Azzaroli (1983) started earlier than originally assumed and cannot indicate the
Fig. 5. Selected fossil remains from the CSG site. a) Mammuthus meridionalis; b) Anancus arvernensis; c) Gazellospira torticornis; d) Gazella borbonica; e) Equus stenonis; f) Hippopotamus sp. Scale bar ¼ 10 mm.
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PlioePleistocene transition (Palombo and Sardella, 2007). Finally, recent identification of Canis sp. in the early Villafranchian of Vialette, indicates that the diffusion of wolf-like dogs across Eurasia was a diachronous event (Lacombat et al., 2008; Sotnikova and Rook, 2010). Besides the First Appearance Datum (FAD) of Canis cf. C. etruscus, the CSG faunal assemblage shows other peculiar features of biochronological value such as the occurrence of gazelle and antelopes (G. borbonica and G. torticornis), coexistence of Anancus arvernensis and M. meridionalis, and the Last Appearance Datum (LAD) of A. arvernensis. Summarizing, the CSG faunal assemblage is definitely middle Villafranchian and characterized by the following taxa: Macaca cf. M. sylvanus florentina COCCHI, A. arvernensis (CROIZET AND JOBERT), M. meridionalis NESTI, Stephanorhinus sp. KRETZOI, E. stenonis COCCHI, Axis lyra (¼ C. philisi SCHAUB), Eucladoceros cf. E. teguliensis (DUBOIS), Croizetoceros ramosus HEINTZ, Cervidae indet., Leptobos sp., G. borbonica DEPÉRET, G. torticornis (AYMARD), Gazella sp., Canis cf. C. etruscus FALCONER, Vulpes cf. V. alopecoides MAJOR, Hyaenidae (possibly Chasmaporthetes HAY), Homotherium sp. and Hystrix cf. H. refossa GERVAIS, Talpa sp. LINNAEUS (Figs. 5 and 6). During the survey attending the drilling activity some new mammal fossil remains were found in the field where most of the CSG FU bones were previously collected. Among them, an upper incisor referable to Hippopotamus sp. (Fig. 5f) is of particular interest and adds a new element to the faunal list. The occurrence of the hippo in late Villafranchian faunal assemblages (Olivola and Tasso FUs; Gliozzi et al., 1997) has been recently questioned and the earliest presence of the taxon in Europe was then considered that from Venta Micena (Spain), correlative to the Pirro Nord FU in Italy (Rook and Martinez Navarro, 2010, with references therein). The FA faunal assemblage was previously considered late Villafranchian in age due to the occurrence of Hippopotamus remains (teeth and fragments of limb bones). Thus the FA fossils were considered slightly younger than CSG, despite the fact that correlation between the fossiliferous levels of CSG and the FA could be supported by field evidence. The new finding of Hippopotamus in CSG allows to refer also the FA assemblage to the middle Villafranchian. Therefore the occurrence of Hippopotamus, reported both in CSG and FA assemblages, assume a remarkable
Fig. 6. Selected fossil remains from the CSG site. a) Chasmaporthetes; b) Canis cf. C. etruscus; c) Homotherium sp.; d) Macaca cf. M. sylvanus florentina. Scale bar ¼ 10 mm.
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biochronological value. In addition, Reimann and Strauch (2008) reported the occurrence of a partial skull of hippo in a middle Villafranchian faunal assemblage from Elis (Peloponnesus, Greece), albeit these authors did not provide a faunal list. Finally, the tooth from CSG confirms the presence of the hippo in the middle Villafranchian in the Italian peninsula, thus demonstrating the diffusion into Europe of an African taxon. Therefore, the dispersal event of the hippo occurred earlier than previously supposed, pre-dating the dispersal of other African taxa during the Early Pleistocene. 5. Discussion The integration of facies analysis and palaeoecological information provided by ostracods and mammal fauna led to the palaeoenvironmental reconstruction of the CSG site. The vertical distribution of facies and ostracod associations points to an aggrading, low-energy environment, with slowly flowing, cold, shallow waters, largely ascribable to an alluvial plain. The w20-mthick marshy succession suggests a long-standing, depressed area of an alluvial plain, probably confined by the bedrock. The bedrock is presently exposed few hundreds meters far from the CSG1 site (Fig. 1) and, in a context of regional aggradation, the marshy depression could be originated by fluvial damming of a recess or a small tributary valley cut into the bedrock. This kind of marshy environment is marginal to the alluvial plain and is largely documented at the foot of the Southern Alps (Ravazzi et al., 2005; Scardia et al., 2010) and the Berici-Euganean hills (e.g. Calderoni et al., 1996; Kaltenrieder et al., 2009; Monegato et al., in press). The marsh at CSG likely developed as a closed basin, where water inflow mainly occurred during floods and was removed by evaporation. Large amounts of organic matter and lignite suggest general humid conditions, during which floods regularly provided water to the marsh and vegetation proliferated along the margin. Episodic negative balance between water inflow and evaporation may have led to moderate salinity increase as documented by the occurrence of noded specimens of C. torosa (Vesper, 1972). Evolution in time led the marsh to be completely filled and to evolve into a low-energy floodplain, with episodic floods and more frequent subaerial exposure. The last facies association in the CSG1 core registers the approach of a sand-bed fluvial-channel, at the base of which bones lie as a lag. Although taphonomic analyses have not been performed yet, bones fragments recovered in the fluvial-channel deposits would suggest a reworking by the water flow for the CSG faunal assemblage. The CSG1 succession ends with the gradual abandonment of the fluvial-channel. A peculiarity of the ostracod assemblage is the concomitant occurrence of epibenthic and hyporheic to stygobitic species in the assemblages D, F, G, and H (Fig. 3). Typically, these species occur in interstitial and groundwater habitats, springs and waters connected to springs, and some of them in a broad range of different freshwater ecosystems. The groundwater hosted in the Mesozoic to Miocene rocks forming the backbones of the Anagni basin (Fig. 1) potentially represents a specific habitat for such taxa and their occurrence in assemblages D and F (Fig. 3) may support the interpretation of a marshy depression confined between the bedrock and an aggrading alluvial plain. The occurrence of Mixtacandona juv. in floodplain settings (Fig. 3, assemblage H) could also be linked to local groundwater characteristics, to the existence of floodplain springs and to the peculiar position of the water body within the floodplain (Ward et al., 1998). Danielopol et al. (1997) studying the interstitial fauna in the Danube Valley near Vienna, reported rich ostracod assemblages during spring and poor assemblages during summer and autumn, corresponding respectively to well oxygenated and hypoxic or anoxic sediment conditions.
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Ascenzi (1993) reported Candona albicans from fine-grained deposits exposed along the rivers’ banks in the study area, but the age of these deposits seems presently to be younger than CSG, because of the different topographic elevation and the available palaeomagnetic constrains (Muttoni et al., 2009). The occurrence of hippos agrees with flowing and/or clear waters, as well as with the presence of plants and grasses. Hippos probably lived in the alluvial plain, which was an important water source for many species, while the occurrence of canids, hyaenids, large equids, and gazelles suggests the presence in the area of prairies and grasslands. Such a scenario can be supported also by the occurrence of M. meridionalis with a molar teeth pattern adapted to grazing grass and other types of hard vegetation. As suggested by different authors (Palmqvist et al., 2003; Russo Ermolli et al., 2010), the living African hippo and also the Pleistocene Hippopotamus antiquus cannot be considered tout court as indicators of warm climate conditions, but its occurrence is suitable to mild conditions. At present, only general palaeoenvironmental considerations can be provided by the vertebrate fossil record from CSG.
6. Conclusions Recent drilling and field activities at the CSG faunal site provided a new stratigraphic data and fossil bones. The CSG1 core, drilled few meters above the local base-level to a depth of 40 m, allowed to recover a previously unknown sedimentary succession. The vertebrate-bearing level, known previously from surface exposure, was detected in the CSG1 core at 5.10e4.90 m below the ground level. The integration of facies analyses, micro- and macropalaeontological observations has led to a more detailed interpretation of the palaeoenvironmental settings of the CSG area in the very early Pleistocene, largely pointing to a low-energy alluvial plain with prairies and grasslands, fed by sand-bed rivers. Among the new findings, an upper incisor of Hippopotamus was collected in the field. This record has a valuable biochronological importance, and it enables pre-dating the occurrence of this taxon to an earlier moment of the Early Pleistocene, witnessing a dispersal event from Africa into Europe more than 2 Ma ago. Palaeomagnetic and palaeobotanical analyses are in progress in order to provide a more complete scenario with firm chronologic constraints.
Acknowledgments We wish to thank Annalisa Zarattini (Soprintendenza per i Beni Archeologici del Lazio) who authorized ongoing field activity, Pierluigi Friello for the technical assistance during the drilling work, the Micropalaeontological Laboratory at Roma Tre University for providing access to their facilities, and Sergio Lo Mastro (Roma Tre University) for the SEM pictures. Italu Biddittu, Laura Bruni, Amalia Faraci, and Barbara Saracino helped during the different steps of the research. Mauro Cremaschi, Massimiliano Ghinassi, Giovanni Monegato, and Giovanni Muttoni are thanked for the useful comments and discussions on the early versions of the manuscript. We want also to thank Roberto Chiararia, Director of “Convitto Nazionale Regina Margherita” of Anagni, for providing assistance and facilities. Research was financially supported by Banca di Credito Cooperativo Anagni, by MIUR Grants “Ricerca di Ateneo federato di Scienze e Tecnologia AST Sapienza 2007” (Project: “I mammiferi del Pleistocene Inferiore italiano: evoluzione, migrazioni, biocronologia”; Resp.: R. Sardella), by MIUR IsIPU “funding 2008e2010”.
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