Echinoderms from the Miocene of Chile Manfred KUTSCHER (Sassnitz, Germany) Christian NEUMANN (Berlin, Germany) Sven NIELSEN (Berlin, Germany) Mike REICH (Göttingen, Germany) Loïc VILLIER (Marseille, France)
GZG
Introduction and material A diverse assemblage of echinoderms is collected from more than 20 Late Miocene localities outcropping along the central coast of Chile (Fig. 1). Three stratigraphical units were sampled: (1) the wide-ranging Navidad Fm. (Fig. 2) found approximately 130 km southwest of Santiago and further south; (2) the Ranquil Fm. on Peninsula Arauco; and (3) the Lacui Fm. on Chiloé Island. The samples yielded an unexpected association of echinoderm taxa, which probably resulted from the mixing of shelf and bathyal sediments.
Stratigraphy and environmental setting Planktic foraminifers collected from the Navidad, Ranquil, and Lacui Formations reveal that these deposits are Tortonian and Messinian in age (Late Miocene; 11.2-5.3 Ma; cf. Fig. 3). For most of the sections studied, the concurrent range of the index taxa (Globigerina apertura, Neogloboquadrina acostaensis, N. pachyderma, N. continuos and Globoquadrina dehiscens) characterize the Zone N16 of planktic Foraminifera dated as early Tortonian, approximately 10-11 Ma (Finger et al. 2003). Two samples collected from the Ranquil Fm. at Punta el Fraile (FRA) and the Lacui Fm. at Chiloe (CUC) yielded Pulleniatina primalis and therefore range into the Messinian (N17b FAD in Finger et al. 2003). The associations of ostracods and benthic foraminifers indicate reworking and mixing of sediments from various stratigraphic units and environmental settings (Fig. 4). This suggests downslope mixing and deposition at lower middle bathyal (1,0001,500 m) and lower bathyal depths (1,500-2,000 m). Data support a Late Miocene scenario similar to the modern continental margin landward of the Peru–Chile Trench, where deep basins episodically receive sediments displaced from shallower depths (Finger et al. 2003).
Fig. 1: Sampled localities of the Navidad Formation and comparable units (from Nielsen et al. in press).
Fig. 2: The Navidad Formation (locality RAP). Fig. 8: Astropectinidae, gen. et sp. indet. – Locality PPP (Navidad Fm).
Age Fig. 10: Ophiomusium sp., oral side – Locality MAP (Navidad Fm).
Fig. 5: Brissopsis valdivianus (Philippi, 1887), apical – Locality VAL (Santo Domingo Fm).
Results
IR
Fig. 7: 4 specimens of Philipaster sp. nov., apical – Locality CUC (Lacui Fm).
Fig. 11: Holothurian interradial element (outer and inner view) of the Apodida (?Chiridotidae) – Locality RAP (Navidad Fm).
Asteroidea (Fig. 8): A fragment of an undetermined astropectinid form probably close to Tethyaster and numerous dissociated plates extracted by sieving of the sediment represent the first mention of Neogene starfishes from South America. First Cenozoic asteroid remains from South America were reported by Tinoco (1963) and Bertels (1965) from Paleocene sediments of Brazil and Argentina. Almost all Chilean remains belong to Astropecten sp. and the undetermined astropectinid. Less common fragments are the marginal plates of Luidia sp. and an undetermined goniasterid. Astropectinid and luidid starfishes are active predators commonly encountered in soft, sandy bottom where they feed mainly on mollusks. Today, a similar association is found in shallow waters (10-200 m) along the western coast of America (Maluf 1987). Echinoidea (Figs. 5-7): Echinoids are represented by the families Arachnoididae (Philipaster, Fig. 6-7), Schizasteridae (Schizaster), Brissidae [Brissopsis valdivianus (Philippi); Fig. 5], as well as cidaroid spines. For the first time, a species of the genus Philipaster, so far known only from the Miocene of South Australia, is recorded from Chilean sediments (Navidad Fm.). The record of the new species of Philipaster is of particular palaeobiogeographic interest. The genus Philipaster belongs to the clade Fossulasteridae erected by Wang (1994). All members of this group have previously been reported exclusively from the Australian continent. The so far single species of Philipaster was P. morgani (Cotteau) from the Late Oligocene of Mount Gambier. Extant Arachnoididae all live in tidal zone whereas Schizaster and Brissopsis are generally (with exceptions) encountered deeper on the shelf. The association of Miocene echinoids thus mixes taxa from distinct environmental setting produced by transport of shallow shelf sediments into the bathyal environment. Holothuroidea (Fig. 11): We report here the first occurrence of holothurian remains from Chile and the first record of isolated calcareous ring elements from Cenozoic sediments worldwide. The disarticulated interradial element of the calcareous ring from the Navidad Fm. can be assigned to the Apodida and probably the Chiridotidae. Chiridotid sea cucumbers are often epi- and/or infaunal inhabitants of soft and sandy bottom sediments. Three Recent chiridotid species of the genera Chiridota, Taeniogyrus, and Trochodota are present in Chilean waters (Pawson 1964, 1966), but it seems that they are particularly rare today on the western coast of Central America, where Maluf (1987) reported only three occurrences. These comparable Recent species are known in depths up to 200 m: Chiridota pisanii Ludwig – 0-100 m, Taeniogyrus contortus (Ludwig) – 0-200 m, Trochodota purpurea (Lesson) – 0-50 m. The occurrence of chiridotid sclerites in Miocene bathyal sediments thus again reflect the export of shallow sediments into the bathyal zone. Acknowledgement S. Nielsen gratefully acknowledges funding by the University of Hamburg and Deutsche Forschungsgemeinschaft (DFG) grant Ba 675/25.
Lacui Fm
N19 N18
Messinian
N17a b II a
Tortonian
Fig. 9: Ophiomusium sp. – Locality MAP (Navidad Fm).
Navidad Fm
N19/20
Zanclean
Ophiuroidea (Figs. 9-10): Ophiuroids are present with species of the Ophiuridae (Ophiomusium and Ophiura), Euryalina, and Ophiodermatidae (Navidad Fm.). Extant ophiodermatids are inhabitant of shelf environments. Euryalina have a wide depth range but are most frequently encountered on shelf and bathyal sea-bottoms. The species of the ophiurid genera Ophiomusium and Ophiura found today along western coasts of America live in rather bathyal environments (Maluf 1987). The ophiuroid assemblage thus corroborates the hypothesis of a mixing of shelf and bathyal sediments.
sponsored by:
Placenzian
Planktic Ranquil Fm Foram Zone
FRA FRM LEB RAN RQT LBZ MAT NAV PPN PPP RAP CHO CUC PCB PNH
Fig. 6: Philipaster sp. nov., apical – Locality CUC (Lacui Fm).
N16
I
N15
Serravallian
N14 N13
Fig. 3: The age interval for sections investigated in this study, as determined from the concurrent ranges of their planktic foraminifera. Note that most of the intervals shown have only the lower part of Zone N16 in common (darker shading), and several are restricted to it. FRA I and II are stratigraphically distinct samples. PNH did not yield any planktic foraminifera (from Finger et al. 2003).
Fig. 4: Division of localities among environmental settings. Int: Intertidal, Sw: shallow water, Dw: deep water (from Nielsen et al. in press).
References Bertels, A. 1965. Noticia sobre el Hallazgo de restos de Equinodermos en el Paleoceno de General Roca (Pcia. Rio Negro). [On microscopic echinoderm remains from the Paleocene of the Roca Formation (Rio Negro)]. Ameghiniana 4 (3): 84-99. Finger, K. L., Encinas, A., Nielsen, S. & Peterson, D. 2003. Microfaunal Indications of Late Miocene Deep-Water Basins off the Central Coast of Chile. In 10°Congreso Geológico Chileno, Concepción, Chile. Extended abstracts, CD-Rom: 8 pp. Nielsen, S. & DeVries, T. 2002. Tertiary Xenophoridae (Gastropoda) of western South America. The Nautilus 116: 71-78. Nielsen, S., DeVries, T., Encinas, A. & Finger, K. L. in press. Towards an understanding of the age of the Navidad Formation. Maluf, L. Y. 1987. Composition and distribution of the Central eastern Pacific echinoderms. Technical reports, Natural History Museum of Los Angeles County 2: 242 pp. Pawson, D. L. 1964. The Holothuroidea collected by the Royal Society Expedition to Southern Chile, 1958-1959. Pacific Science 18 (4): 453-470. Pawson, D. L. 1966. Holothuroidea from Chile [Report No. 46 of the Lund University Chile Expedition 1948-1949]. Sarsia 38: 121-145. Tinoco, I. de M. 1963. Fragmentos de equinodermas do Paleoceno de Pernambuco. [Echinoderm fragments from the Paleocene of Pernambuco]. Arquivos de Geologia (Gabinete de Micropaleontologia), Universidade do Recife 4: 49-63. Wang, Chia-ching 1994. Phylogenetic analysis of the fossulasterid echinoids (Order Clypeasteroidea) from Australia. Journal of the Geological Society of China [= Huikan, Zhongguo-DishiXuehui] 37 (2): 225-246.
Addresses: M. Kutscher: Dorfstr. 10, D-18546 Sassnitz, Germany; e-mail:
[email protected] C. Neumann: Museum für Naturkunde Berlin, Institut für Paläontologie, Humboldt Universität, Invaliden-Str. 43, D-10115 Berlin, Germany; e-mail:
[email protected] S. Nielsen: Institut für Geologische Wissenschaften, Freie Universität Berlin, FB Paläontologie, Malteser-Str. 74-100, Haus D, D-12246 Berlin, Germany; e-mail:
[email protected] M. Reich: Geowissenschaftliches Zentrum der Universität Göttingen, Abt. Geobiologie, Goldschmidt-Str. 3, D-37077 Göttingen, Germany; e-mail:
[email protected] L. Villier: Centre de Sédimentologie-Paléontologie / UMR CNRS 6019 Université de Provence Bâtiment de Sciences Naturelles, Place Victor Hugo Case 67, F-13331 Marseille cedex 03, France
