Reconsideration of the Mytilinii fossiliferous Basin ...

5th International Symposium on Eastern Mediterranean Geology Thessaloniki, Greece, 14-20 April 2004

Reconsideration of the Mytilinii fossiliferous Basin, Samos, Greece Koufos G.D., Kostopoulos D.S., Vlachou Th.D. & Sylvestrou I.A. Department of Geology, Aristotle University, GR-54124, Thessaloniki, Greece, [email protected], [email protected] Keywords: Late Miocene, lithostratigraphy, magnetostratigraphy, biochronology

Introduction Although the fossiliferous deposits of the Mytilinii Basin in Samos island, Greecce were known since the second half of the 19th century (Forsyth-Major 1888) providing a great amount of mammalian fossils (Solounias 1981 and literature listed), the stratigraphic position, the homogeneity and the age of the Samos fauna(s) are still discussed. An extensive field-work, starting in 1993, allowed us to locate several fossiliferous sites, and to re-locate most of the old referred quarries. Palaeontological excavations in association with new lithostratigraphic research, palynological analyses and magnetostratigraphic study on the eastern part of the island, revise and complete previous works. This paper summarizes most of the new available data on the mammal localities and their faunal content, along with several litho- and magneto-stratigraphic as well as biochronological conclusions.

Lithostratigraphy Most relevant works grouped the Neogene sediments of Mytilinii Basin in four to five lacustrine-fluviatile formations (Theodoropoulos1979; Meissner 1979; Weidmann et al. 1984): Basal conglomerate, Pythagorion Fm (marl, lignite, tuffs, fresh-water massive limestone), Hora Fm (thin bedded fresh-water limestone), Mytilinii (=“Mytilini”)Fm (clastic sediments and tuffs) and Kokkarion Fm (mainly algal limestone). Between the Basal conglomerate and the main fresh-water limestones, which represent the upper part of the Pythogorion Fm and the entire Hora Fm, there is a lithological complex at about 40 m thick, consisting of fossiliferous gray-whitish fresh-water limestone with Planorbis, green clay with intercalations of yellow marl and lignite, a 3m thick basalt flow and a 20 m light-green tuffaceous horizon of lahar type. The lithological dissimilarity of these deposits and their difference from the underlying and overlying beds, suggest their separation as a distinct stratigraphic unit. Both the upper part of the Pythagorion Fm and the entire Hora Fm, are consisted of fresh-water massive to thin-bedded limestone and, contrary to previous suggestions, it seems impossible to locate a clear boundary between them. Therefore, and following Theodoropoulos (1979) we suggest including the entire limestone series into the same lithostratigraphic unit. Moreover the contact between Mytilinii and Hora Fm did not reveal any discordance and it is rather transitional.

Mammal Localities and Faunas During the new field-works eight fossiliferous sites have been discovered in the Mytilinii basin. The first two are placed in the lower part of the Mytilinii Fm and correspond to Q6 and Qx of B. Brown (Solounias 1981) but the few collected material cannot give significant information at the moment (Kostopoulos et al. 2003). The locality “Mytilinii 4”-MLN, discovered by Koufos et al. (1997) in the southern outcrops of Potamies ravine seems to be identical with B. Brown’s Q4 (Kostopoulos et al. 2003).

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5th International Symposium on Eastern Mediterranean Geology Thessaloniki, Greece, 14-20 April 2004 The available field data suggest the presence of three fossiliferous horizons in the upper part of Mytilinii Fm. The first and older one is located in the Potamies ravine (northern outcrops) including the localities “Potamies” of Forsyth-Major (1894), Q2 and Q3 of B. Brown (Solounias 1981), localities S2, 3, 4 of Solounias (1981) and locality “Mytilinii-3” (MYT) of Koufos et al. (1997). The location of the latter one matches that of B. Brown’s Q3 and the two fossiliferous localities are considered to be identical (Koufos et al. 1997, Kostopoulos et al. 2003). S4 of Solounias (1981) is probably situated at the same level. The second fossiliferous horizon is located in the Andrianos ravine, where Koufos et al. (1997) retrieved four fossiliferous sites, named “Mytilinii 1”-A, B, C and D (MTLA, MTLB, MTLC and MTLD). MTLA coincides with locality “Andrianos” of Forsyth-Major (1891, 1894) and Melentis (1969), while MTLD are the leftovers of an old excavation directly correlated to Q1 of B. Brown (Solounias 1981, Kostopoulos et al. 2003). The third fossiliferous level corresponds to the locality Q5 of B. Brown and locality L of Acker, both known as being from Limitzis district (Solounias 1981). In 1994, the locality Q5 has been re-found and very few surface fossil fragments have been collected (e.g. Hipparion sp. and Pliocervus sp.). The determination of the available material from each locality gives the following preliminary faunal lists: MTLA. Pseudomeriones cf. pythagorasi, Promeles sp., Hyaenotherium wongii, Metailurus major, Orycteropus gaudryi, Hipparion cf. proboscideum. Hipparion dietrichi, Hipparion sp. (small size), Hipparion aff. elegans, Dicerorhinus pikermiensis, Microstonyx major, Samotherium major, Miotragoceros vallencienesi, Palaeoryx major, Tragoportax sp., Gazella sp.1, Gazella sp. 2, “Protoryx” sp., Pseudotragus parvidens, Antilopinae indet., Ovibovinae indet., Bovidae indet. MTLB. Pseudomeriones cf. pythagorasi, Hyaenotherium wongii, Orycteropus gaudryi, Choerolophodon pentelici, Bunolophodon sp., Hipparion brachypus, Hipparion dietrichi, Hipparion sp. (small size), Dicerorhinus cf. pikermiensis, Samotherium major, Palaeotragus cf. rouenii, “Protoryx” sp., Gazella sp.1, Gazella sp. 2 MTLC. Hyaenotherium wongii, Hipparion sp., Pliohyrax sp., Dicerorhinus s p . , Microstonyx sp. , Samotherium major, “Protoryx” sp., Gazella sp . MYT. Hipparion aff. mediteraneum, Hipparion sp.1 (small size), Hipparion sp.2, Dicerorhinus cf. pikermiensis, Samotherium cf. boissieri, Protoryx cf. laticeps, cf. Pseudotragus. MLN. Testudo sp., Carnivora indet., Hipparion mediterraneum, Hipparion sp. (medium size), Samotherium cf. boissieri, Palaeotragus sp. ?Protoryx sp., ?Boselaphini indet.

Magnetostratigraphy All the known mammalian fossiliferous sites of Samos Island are situated in the Mytilinii Fm, which overlies the limestones series and underlies the Kokkarion Fm. 178 sampled horizons from two main and five secondary sections that cover the entire Mytilinii Fm have been magnetostratigraphically studied and correlated among them. The more than 200 m synthetic magneto-stratigraphic column has been correlated with GPTS providing a new chronological frame (Kostopoulos et al. 2003). The results of this study are given in Figure 1. The Mytilinii Fm covers a time span of about 1.4 Ma; its top corresponds to chron C3Ar (~6.7 Ma) and its base to the boundary C4n/C4r (~8.1Ma) (Fig. 1). The main fossiliferous level of the Andrianos ravine is most probably correlated to chron C3Br.1n (7.13-7.17 Ma). Samples from the locality MYT, provide reverse polarity, and they are most probably correlated to chron C3Br.2r (7.17-7.35 Ma). Somewhat older appears the locality MLN, dated magnetostratigraphycally at C4n.1n/1r indicating an age between 7.45-7.65Ma.

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Figure 1. Correlation of the synthetic magnetostratigraphic column of Mytilinii Basin, Samos with GPTS (after Kostopoulos et al. 2003). Brown’s quarries are indicated with “Q”; L=Limitzis; A=”Andrianos”; G=locality “G”; S=micromammalian sites; MTLA/B/C/D, MYT, MLN following Koufos et al. 1997; MT, MMB, WB, GB, OMB= members of Mytilinii Fm according to Weidman et al. 1984.

Biochronology Four to five successive mammalian assemblages have been recognized in the whole Mytilinii Fm (Table 1). The fossil assemblage of Qx, G, and most probably Q6 constitutes the oldest known mammal record on the island, corresponding to an age between 7.8-8.0 Ma. In the local scale, this faunal assemblage underlies that of the mammal assemblage from MLN/Q4 dated to the upper part of Early Turolian (MN 11) with an estimated magnetostratigraphic age between 7.45-7.65 Ma. The overlain faunal assemblage corresponds to the localities MYT/Q3 and probably Q2 with an age of about 7.3 Ma. The faunal character of MYT/Q3 appears different from that of MLN/Q4, having an intermediate aspect towards and rather closer to that of the next assemblage, represented by the localities of “Andriano(s)”/MTLA,B,C and Q1/MTLD. The new mammal collection from the latter sites shows a great resemblance to those of late Middle Turolian (MN 12) age from East Mediterranean. A magnetostratigraphic age between 7.1-7.2 Ma is estimated for this assemblage. The local succession ends with the faunal assemblage of Q5 and locality L with a predicted magnetostratigraphic age between 6.7-7.0 Ma for the first one. Table 1 summarizes all previous works and the proposed stratigraphic position and ages of the Samos mammal localities.

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Table 1. Stratigraphic position and ages of old and new fossiliferous sites from Mytilinii basin, Samos, in association with the related radiometric dates (after Kostopoulos et al. 2003).

References Forsyth-Major C.I. (1888). Sur un gisement d’ ossement fossils dans l’ île de Samos contemporains de l’ age de Pikermi. Comptes Rendus Hebdomadaires Seances Academie Sciences, 107: 1178-1181. Kostopoulos D.S., Sen S. & Koufos G.D. (2003). Magnetostratigraphy and revised chronology of the late Miocene mammal localities of Samos, Greece. International Journal Earth Sciences (in press) Koufos G.D., Syrides G., Kostopoulos D.S., Koliadimou K.K., Sylvestrou I., Seitanides G. & Vlachou D. (1997). New excavations in the Neogene mammalian localities of Mytilinii, Samos island, Greece. Geodiversitas 19 (4): 877-884. Meissner (1976). Das Neogene von Ostsamos Sedimentationsgeschichte und Korrelation. Neues Jahrbuch Geologie Palaeontologie Abh., 152: 161-176. Solounias N. (1981). The Turolian Fauna from the island of Samos, Greece. Contribution Vertebrate Evolution, 6: 1-232. Theodoropoulos D. (1979). Samos island, geological map 1:50.000, with explanations. Inst. Geol. Mining Research, Athens. Weidmann M., Solounias N., Drake R.E. & Curtis J. (1984). Neogene stratigraphy of the Mytilini Basin, Samos island , Greece. Geobios, 17 (4): 477-490.

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