Δελτίο της Ελληνικής Γεωλογικής Εταιρίας τομ. ΧΧΙΧ/Ι, 80-86,2006 Bulletin of the Geological Society of Greece vol. XXIX/1, 80-86,2006
PLIOCENE MOLLUSCS TAXONOMIC DIVERSITY AS A TOOL FOR THE CLIMATIC-OCEANOGRAPHIC RECONSTRUCTION AND STRATIGRAPHY. TWO EXAMPLES FROM THE EASTERN MEDITERRANEAN* E. Koskeridou1
1 National and Kapodistrian University of Athens, Faculty of Geology and Geoenvironmeni:, Department of Historical Geology - Paleontology, ekosker@geol. uoa.gr
ABSTRACT Due to their high extinction rate, the Molluscs of the Pliocene in the Mediterranean, resulted potentially useful as a tool for climatic-oceanographic and chronological inferences. In the present study, we document the possibility of application of the model of Raffi and Monegatti (1993) in the region of Eastern Mediterranean, by studying two examples from the Hellenic area and Cyprus. This model concerns the extinction events of Molluscs of Pliocene, separating 4 dif ferent units of Molluscs with different climatic-oceanographic importance. It is docu mented that the two selected sections, Atsipades in central Crete and Athienou in southern Cyprus, give elements for the correlation of their deposits with this model. The Atsipades section is connected with the first significant extinction event, at the Mollusc Units of Raffi and Monegatti, resulting from the first important Pliocene cooling phenomenon of our hemisphere. The Athienou section is connected with the MPMU2 unit of Raffi and Monegatti, between the first and second distinctive extinction events of the Pliocene Molluscs. Key words: bivalvia, ecobiostratigraphy, Mediterranean, Pliocene, taxonomic diversity.
ΠΕΡΙΛΗΨΗ To μεγάλο ποσοστό εξαφάνισης των Μαλακίων του Πλειόκαινου, το οποίο ξεπερνά το 30%, δίνει τη δυνατότητα της χρήσης τους για την αναγνώριση κλιματικών-ωκεανογραφικών και χρονολογικών στοιχείων. Στην παρούσα εργασία, η δυνατότητα χρήσης του μοντέλου των Raffi & Monegatti (1993) στην περιοχή της ανατολικής Μεσογείου, αποδεικνύεται από τη μελέτη δύο παραδειγμάτων από τον Ελλαδικό χώρο και την Κύπρο. Το μοντέλο αυτό αφορά στα βιοοτρωματογραφικά γεγονότα εξαφάνισης των Μαλακίων του Πλειόκαινου, διακρίνοντας 4 ενότητες Μαλακίων διαφορετικής κλιματικής-ωκεανογραφικής σημασίας. Δύο περιοχές που έχουν καλά μελετηθεί
*Η ΣΥΜΒΟΛΗ ΤΗΣ ΤΑΞΙΝΟΜΙΚΗΣ ΚΑΤΑΝΟΜΗΣ ΤΩΝ ΜΑΛΑΚΙΩΝ ΤΟΥ ΠΛΕΙΟΚΑΙΝΟΥ ΣΤΗΝ ΚΛΙΜΑΤΙΚΗ- ΩΚΕΑΝΟΓΡΑΦΙΚΗ ΑΝΑΣΥΣΤΑΣΗ ΚΑΙ ΤΗ ΣΤΡΩΜΑΤΟΓΡΑΦΙΑ. ΔΥΟ ΠΑΡΑΔΕΙΓΜΑΤΑ ΑΠΟ ΤΗΝ ΑΝΑΤΟΛΙΚΗ ΜΕΣΟΓΕΙΟ Ε. Κοσκερίδου Εθνικό & Καποδιστριακό Παν/μιο Αθηνών, Τομέας Ιστορικής Γεωλογίας & Παλαιοντολογίας, Τμήμα Γεωλογίας & Γεωπεριβάλλοντος, Παν/πολη Ζωγράφου
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από αυτή την άποψη, η τομή Ατσιπάδες Ηρακλείου Κρήτης και η τομή Αθηένου Κύπρου, δίνουν στοιχεία για το συσχετισμό των αποθέσεων τους με το μοντέλο αυτό. Η τομή Ατσιπάδες συσχετίζεται με το πρώτο βιοστρωματογραφικό γεγονός εξαφάνισης των taxa των βενθονικών Μαλακίων των ενοτήτων των Raffi & Monegatti το οποίο μπορεί να θεωρηθεί ως αποτέλεσμα του πρώτου γεγονότος ψύχρανσης κατά το Πλειόκαινο. Η τομή Αθηένου μπορεί να συσχετιστεί με την MPMU2 ενότητα των Raffi & Monegatti, μετά το γεγονός της πρώτης εξαφάνισης και πριν το γεγονός της δεύτερης εξαφάνισης των Μαλακίων του Πλειόκαινου.
1. Introduction knowledge of the statigraphic range of The reduction in taxonomic diversity of Molluscs calibrated by biostratigraphic marine Molluscs throughout the Pliocene and magneto-biostratigraphic data in the Mediterranean, has been report could well play an important role in the ed already by Levi (1900) (in Ruggieri, stratigraphie classification of sections 1962). Up to the 50's it was believed that characterize shallow water environ that the Pliocene faunas were stable ments, when the calcareous plankton and were represented by warm-water taxa, which they were dis 8t öl 3304 umis appeared in the upper ... .jj,.... 1 most Piacenzian or at ir 1 ΜθβΗΒΗΟΤΜΚΤί Ο "te li 1 the P/P boundary. In ; * 2' 1 the 60's (Ruggieri, 1962, 1967), it was "*•« m clarified that Pliocene Ζ § }/?... tut : g§ is characterized by £2 çj&£* | the progressive reduc LU boreal —ι tion of Molluscs taxo Cu J506 ·••» MPMU4 S nomic diversity, due MPI*- MPMU3 to progressive climat ism. MMftS ic cooling. Raffi and LU Monegatti (1993) and Ζ VPU * Monegatti and Raffi •"•""•-""''•'• -m
(2001) took into their MP13 ***» ;}t.*
1), of different cli- 7.25- matic-oceanographic importance. They F/g. 7. Mediterranean Pliocene Molluscan units (MPMU) correlated to the Planctonic foraminifera biostratigraphy, to the Standard Global Chrono- recognized that the stratigraphic Scale and to Geomagnetic Polarity Time Scale (Gradstein et al., 2004).
81 E. Koskeridou is absent. ute significantly to this field, for the For the Greek Neogene, an extended Greek area. Nevertheless it is necessary investigation of the faunal succession to extend this study on the Hellenic area has been worked out (Dermitzakis & and on the Eastern Mediterranean. Georgiades-Dikeoulia, 1987). For this purpose, a multi-disciplinary This research has allowed a first approach has to be carried out, includ approach to the analysis of the mollus- ing biostratigraphic, magnetostrati- can taxonomic diversity and a proposed graphic and paleoecological data. biozonation which corresponds to 4 On this frame, we attempted to correlate assemblage biozones and one acme two representative sections (Atsipades zone for the Pliocene. These data gave in central Crete and Athienou in south the possibility of working out a chrono Cyprus), by means of Molluscs sys logical framework for the Greek Plio tematic classification, biostratigraphy cene, based on marine molluscs and in and paleoenvironmental characteristics particularly on the bivalves. with the Mollucsc Units of Raffi and In this work, we make an effort to inves Monegatti. tigate whether the extinction events Further objective documentation based during the Pliocene (according to Raffi on the study of more Pliocene outcrops & Monegatti, 1993) can be recognized of eastern Mediterranean is necessary. and give more precise chronological data in the Eastern Mediterranean too. 2.1. Study area The Atsipades section, is located in 2. Discussion Central Crete, in the southern part of As three major extinction phases have the Hiraklion Basin (sensu Meulenkamp been evidenced during the Pliocene in et al., 1994). It is approximately 80 m the Mediterranean basin, by means of thick, representing a shallowing upward Molluscan fauna, four MPMU were rec sequence from outer shelf marls and ognized by Raffi and Monegatti (1993). sandy marls at the bottom, to shallow As these extinction events were not inner shelf deposits at the top of the followed by recovery phases, a pro section (Fig. 2). gressive decrease in warm-water taxa The biostratigraphical analysis based occurred. Every MPMU was defined on planktonic foraminifera and nanno- by the lack of taxa which disappeared fossils, determined the base of the suc in the immediately previous extinction cession as younger than 3.61 Ma and event and by the presence of the par the top up to 3.21 Ma. ticular taxa which disappears in the suc The fossil assemplages of the greater cessive extinction phase. area, have been recorded by (Symeo- In order to study the applicability of Raffi and Monegatti model, the con trol of systematic classification of the CRETE Mediterranean Pliocene Molluscs, is essential. For Italy, this work has been almost completed with the study of 356 species of infralittoral and cir- calittoral environments. Dermitzakis & Georgiades-Dikeoulia (1987), contrib Fig. 2. Schematic map of Crete indicating the location of the study area
82 Bulletin of the Geological Society of Greece, vol. XXIX/I, 80-86 nidis and Konstant! η id is, 1967, Zacha- biofacies, the correlation with our sec riasse, 1975, Dermitzakis and Geor- tions, have been done only in the parts giades-Dikeoulia, 1983, Koskeridou, that correspond in shallower-water 1997, Koskeridou et al., 2002). zones. The paleoecological analysis based on The second section studied, was foraminifera and molluscs, show that to Athienou, which is situated near the bottom of the section the environ Athienou (South Cyprus) (Fig. 3), at the mental conditions was more typical of southeastern opening of the Mesaoria deeper waters with high productivity and basin to the open sea. At the end of moderate oxygen content (Drinia et al., Pliocene the Mesaoria basin became 2005). The deposits of the middle and a narrow shallow sandy platform (Mc upper part of the sequence, thought, Callum and Robertson, 1990). The are being characteristics of normal Athienou section belongs to Nicosia salinity and high oxygenation environ Formation and it has been studied by ment of the inner shelf. Therefore, rich Koskeridou et al. (2005). In terms of bio- macrobenthic assemblages, including stratigraphy, the section belongs to the Bivalves, Gastropods, Brachiopods, Globorotalia crassaformis Zone (Spaak, Echinoids and Annelids, colonized these 1983) and has a Middle Pliocene age settlements (Koskeridou et al. 2002). as has been proved by the cooccur As for the MPMU, Raffi and Monegatti, rence of the planktonic foraminifera did not use species typical of bathyal species Globorotalia crassaformis and
CYPRUS
Fig. 3. Schematic map of Cyprus indicating the location (A) of the study area
83 E. Koskeridou
Globorotalia bononiensis. The studied contain a rich Mollusc and Brachiopod invertebrate faunal component points fauna. The most dominant representa to very good ecological conditions of tives of the Gastropods and Bivalves are: normal salinity and high oxygenation Neopycnodonte navicularis (Brocchi), and indicates an environment 130m in Glossus humanus (L), Chlamys opercu- depth. laris (L.), Chlamysangelonii (Meneghini), Chlamys glabra L, Amussium crista- 3. Results tum (Bronn), Pecten jacobaeus (L) and The fauna from Atsipades section indi Chlamys flexuosa Poli. The total compo cating the neritic zone, shows an inter sition of the fauna along with the lack esting similarity with this of the first of tropical taxa, the minor appearance appreciable extinction event (immigra of Terebridae and Conidae and the tion and local disappearance) of tropi presence of Neopycnodonte navicularis, cal Mollusc taxa, as these have been allow the emplacement of these depos determined by Raffi ef al. (1989) in the its between the first and the second Mediterranean Pliocene, which approxi extinction event in the Mediterranean mates or just follows the first occur Pliocene, and the assignment to the rence of Globorotalia bononiensis and MPMU2 of Raffi and Monegatti (1993), G. crassaformis. which is in accordance with the bio- These beds are remarkable for their stratigraphical interpretation by the relatively abundant, well-preserved planktonic Foraminifera. macrofossils, mostly bivalves and gas The composition of the Mollusc fauna tropods (Koskeridou ef a/., 2002). The of the two studied sections should presence of Flabellipecten flabelliformis be considered the effect of the first (BR.), Chlamys scabrella (LK.), Dymia incident of falling temperatures during fragilis (KOENEN), Neopycnodonte the Pliocene. The first cooling wave navicularis (BR.) and a minor presence occurred in the Northern hemisphere of Terebridae and Conidae, with the relatively sudden, in high and mid lati species Terebra acuminata (BORSON), tudes, in accord with the first appear Conus (Lautoconus) mediterraneus ance of Globorotalia crassaformis and BRUGUIERE and Conus ventrico- Globorotalia bononiensis and marks the sus GMELIN, has been noticed. The beginning of the Plio-Pleistocene ice absence of the large number of benthic age, with the absence of fully devel molluscan taxa of tropical affinity as oped ice sheets yet. Chlamys latissima (BROCCHI), Callista However the presence of thermophilic italica (DEFR.), Pelecyora gigas (LK.), benthic Molluscs, in the studied sec Pseudoxyperas proaspersa (SACCO), tions, suggests that relatively high tem Tugona anatina (GMELIN) and of peratures (higher than today's) occurred Gastropods Strombus coronatus DEFR., during that era, in the coasts of Cyprus Ficus and Ancilla, is obvious. Therefore, and Crete. the studied fauna allows assignment for A large number of thermophilic taxa the middle and upper part of the sec apparently migrate south, due to that tion, to the limit of the Mediterranean specific event. This mentioned above Pliocene Molluscan Unit 1 and 2 of Raffi event, has been recorder also, in the & Monegatti (1993). coasts of North Atlantic and was a small The deposits of Athienou section, also scale global event.
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4. Conclusions Foraminifera and Molluscs from the The faunal assemblages of two studied Atsipades Section, Central Crete; sections, Atsipades (Central Crete) and Paleoecological Distribution and use Athienou (South Cyprus) suggest that in Paleoenvironmental Assessment. there is possible applicability of the Geobios 38, 315-324. Raffi & Monegatti (1993) model, to the Koskeridou, E., Antonarakou, Α., Drinia, Eastern Mediterranean. H., and Triantaphyllou, M.V., 2002. There are similarities between the con Paleoecological observations on the tained fauna in these two sections and Upper Pliocene deposits of Atsipades the Mollusc fauna diversity patterns Section (C. Crete). Proceedings, 6th which lead to the MPMU zones of the Panhellenic geographical conference previous mentioned authors. of the Hellenic Geographical Society, The deposits of Atsipades and Athienou vol. I: 123-130. sections are well calibrated by biostrati- Koskeridou, E., Vardala-Theodorou, graphical data. The environmental fac G.E., Tsiolakis, E., Panayides, I., tors -except the temperature- that fauna Theodorou, G., and Antonarakou, indicates in these two sections, seems Α., 2005. The marine faunis- to be favourable for tropical taxa, which tic assemblages of the Pliocene are in this case lacking. Also a dras of Paleometocho and Athienou tic decrease in other taxa of Bivalves (Cyprus, East Mediterranean): some and Gastropods is occurred. These palaeoecological aspects. Abstracts, elements lead to the conclusion that 12th RCMNS Congress, Vienna 2005, the Molluscs fauna of these deposits p. 134-136. are connected with the first significant Meulenkamp, J.E., Van Der Zwaan, extinction event, at the Mollusc Units of G.J., Van Wamel, W.A., 1994. On late Raffi and Monegatti, resulting from the Miocene to Recent vertical motions first important Pliocene cooling phe in the Cretan segment of the Hellenic nomenon of our hemisphere. arc. Tectonophysics, 234, 53-72. In order that these observations should Monegatti, P., and Raffi, S., 2001. be effect in Eastern Mediterranean, Taxonomic diversity and stratigraph detailed studies should be carried out ie distribution of Mediterranean in other regions of this area. The results Pliocene bivalves. Palaeogeography, of this work constitute spark on stud Palaeoclimatology, Palaeoecology, ies to the direction of determination of 165, I. 3-4, 171-193. Molluscs extinction patterns of Eastern Raffi, S., and Monegatti, P., 1993. Mediterranean. Bivalve taxonomic diversity through out the Italian Pliocene as a tool for 5. References climatic-oceanographic and strati- Dermitzakis, M.D., and E., Georgiades- graphic inferences. Proc. 1st RCANS Dikeoulia, 1987. Biozonation of the Congr., Lisbon, 1992. -Ciencias della Neogene invertebrate megafauna of Terra, 12 : 45-50. the Hellenic area. Ann. Inst. Geol. Ruggieri, G., 1950. Contribuzione alla Pubi. Hungarici, (Proceed.), Vol. LXX, conoscenza della malacofauna e p.125-135. della stratigrafia del Pliocene e del Drinia, H., Koskeridou, E., and Antona- Quaternario. Giorn. Di Geol. 21 : rakou, Α., 2005. Late Pliocene Benthic 65-90.
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Ruggieri, G., 1962. La serie marina plio Symeonidis, N., Konstantinidis, D., 1967. cenica e quaternaria della Romana. Observations on the Neogenic for A cura della Camera de Com. Ind. E mations of Central Crete, Annales Agric. De Forlì, 1-76. Géologiques des Pays Helléniques, Ruggieri, G., 1967. The Miocene and 19, 657-688. later evolution of the Mediterranean Zachariasse, W.J., 1975. Planktonicfora- Sea, in Adams & Ager, D.V., Aspects miniferal biostratigraphy of the Late of Tethyan Biogeography, Syst. Neogene of Crete. Utrecht Micropa- Assoc. Pubi. 7: 283-290. leontological Bulletin, 11, 171 pp.
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