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F u n 2 d 6 la serena octubre 2015 ada en 19 Sequence Stratigraphy affinities of the Quiriquina Formation (Late ) from central Chile.

Christian Salazara *, Wolfgang Stinnesbeckb, Luis Arturo Quinzio-Sinnc, Miguel Álvarezd a Área Paleontología, Museo Nacional de Historia Natural, Parque Quinta Normal s/n, Casilla 787, Santiago, Chile b Institut für Geowissenschaften, Universität Heidelberg, INF 234, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany cDepartamento Ciencias de la Tierra, Universidad de Concepción, 160 C Concepción, Chile dInstitut für Nutzpflanzenwissenschaften und Ressourcenschutz (INRES), Universität Bonn, Nussallee 9, 53115 Bonn, Germany

*email: [email protected]

Abstract. The () Quiriquina Concepción (Salazar 2004). The Quiriquina Formation Formation in Central Chile is well recorded around the Bay (Maastrichtian) in the Bío-Bío region was defined by Biro of Concepción and assigned to the late Early to Late (1982); the unit was deposited in a fore-arc basin in the Maastrichtian, based on a diverse ammonite assemblage. western margin of the Chilean Coastal Range (Stinnesbeck Species richness and abundance of ammonoids are high 1986). throughout the Quiriquina Formation but gradually decline in the uppermost 10 meters of the section. No ammonoids 3 Stratigraphy and Facies are recorded from the last 5 meters of the unit. The following three biozones are distinguished (from base to For the present research we analysed thirteen sections in top): Zone of Baculites anceps, Zone of Eubaculites the Concepción area. Four lithologically-defined units are carinatus (subdivided into the Menuites fresvillensis and differentiated (Figure 1; from base to top): Kitchinites darwini sub-biozones), and a Zone without baculitids (subdivided into the Hoploscaphites constrictus (a) Basal Conglomerate: the lowermost 15 meters biozone and a zone without ammonites. The assemblage correspond to a polymictic conglomerate, which is shows an Indopacific character, but endemic, composed of rounded to angular clasts of schist, meta- cosmopolitan as well as Europe-Tethyan elements are also sandstone and quartz. In the upper part of this unit, a present. Lithologies of the Quiriquina Formation are sandstone horizon of 0.3 m presents planar cross- siliciclastic and consist of a basal conglomerate, between stratification and contains imbricated clasts. The basal a few centimetres and 15 metres thick, overlain by yellow conglomerate represents high energy shoreface facies cross-bedded sandstone, green siltstone with bivalve filling up an irregular paleorelief (Figure 1 and 2). coquina layers (Cardium, Pacitrigonia) and a unit of green mottled siltstone with limestone concretions. These (b) Yellow Sandstone: A 6.5 m thick yellow sandstone lithologies represent a retrogradational pattern of with planar cross-bedding and interbedded conglomeratic shoreface to offshore facies which resulted from a sea level lenses overlies the basal conglomerate, indicating middle- rise (transgression) during the late Early Maastrichtian. upper shoreface facies with a sporadic decrease of energy The energy of transgression decreases upsection and low (Figure 1). A centimetre-thick layer with abundant small energy environments prevail during the Late Maastrichtian part of the section. fragments of dark mica (biotite) is intercalated in the upper part of the unit and represents a short period of low energy Key words: Maastrichtian; facies; ammonites; environment, in which mica was washed in from the biostratigraphy; palaeobiogeography. weathering metamorphic basement rocks. Baculites anceps was recorded by Salazar et al. (2010). The yellow 1 Introduction sandstone represents a coastal shallow marine environment (Figures 1 and 2). Upper Cretaceous sedimentary succession in central Chile are recorded from Algarrobo (33° S.) to Arauco Península (37° S.), and are well exposed and fossil-rich in the bay of

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Figure 1. Sediment sequence in the type section of the Quiriquina Formation at Las Tablas on Quiriquina Island, with ages, lithological units, ammonite zones, ranges of ammonite species and species richness analysis.

Figure 2. Sequence stratigraphic correlation of sections in the Concepción Bay area

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(c) Coquina Unit: A 10 m thick unit of glauconitic green (Neophylloceras) surya, Hoploscaphites constrictus sandstone overlies the yellow sandstone with a sharp but quiriquiniensis) (Figure 1; Stinnesbeck 1986, 1996; conformable contact and contains intercalated 5 mm to 0.3 Salazar et al. 2010) up to approximately 5 m below the top. m thick resistant coquina layers. Their faunal assemblage Trace fossils (Teichichnus, Zoophycos) are especially is dominated by Pacitrigonia hanetiana and Cardium abundant in the uppermost 2-3 meters of the Quiriquina (Bucardium) acuticostatum. The nautiloid Eutrephoceras Formation but macrofauna is scare and consists exclusively dorbignyanus is also present (Nielsen and Salazar 2011). of detritus-feeding bivalves (Stinnesbeck 1986, 1996). Ammonites are represented by Eubaculites carinatus, Menuites fresvillensis, Pachydiscus (Pachydiscus) The Quiriquina Formation is truncated by the Cerro Alto jacquoti, Pachydiscus gutierrezi, Kossmaticeras erbeni, Formation of age (Frutos et al., 1982). The Maorites densicostatus, Grossouvrites gemmatus, contact between both units is characterized by an undulose Grossouvrites joharae, Anagaudryceras politissimum, erosive surface and was interpreted by Stinnesbeck (1986, Gaudriceras kayei, Hypophylloceras (Neophylloceras) 1996) as a disconformity (Figure 1 and 2). inflatum and Baculites huenickeni (Figure 1; Stinnesbeck 3 Sequence Stratigraphy 1986, 1996; Salazar et al. 2010). Four parasequences are identified in the Quiriquina The coquina layers represent tempestites that formed Formation by a retrogradational pattern of depositional within the storm wave base (Stinnesbeck 1986). High facies (Figure 2). Parasequences 1 to 3 were determined at energy conditions and shallow marine environments of Las Tablas and are also recognized in numerous other less than 20 m depth are also indicated by the abundance sections in the area (Figure 2). They correspond to the of Pacitrigonia hanetiana and Cardium (Bucardium) basal conglomerate (parasequence 1), the yellow cross- acuticostatum (Figure 1). Particularly the trigoniids bedded sandstone (parasequence 2) and the coquina unit occupied shallow-water habitats of less than 10-15 m (parasequence 3); they represent shoreface facies of depth (Stanley 1977), or less than 30 m depth in decreasing energy. Parasequence 4 corresponds to the silty transgressive environments (Francis & Hallam 2003). The sandstone with calcareous sandstone concretions and unit with abundant coquina layers represents transgressive reflects offshore transitional facies (Figure 2). marine high-energy environments within reach of the storm wave base (Figure 2). Based on the vertical stacking pattern of the 4 parasequences described above, a single depositional (d) Silty sandstone with calcareous Sandstone sequence is recognized in the Quiriquina Formation. It Concretions: The coquina unit grades into a 35 meter-thick consists of a TST, which is characterized by a unit of intensively bioturbated, green silty sandstone with retrogradational stacking pattern of parasequences 1 to 3. levels of calcareous sandstone concretions that reach Parasequence 3 contains the maximum flooding surface between 0.2 and 1 m in diameter and are aligned parallel to (mfs) (Figure 2). The HST is formed by the stratification (Stinnesbeck, 1986; Salazar et al. 2010). The retrogradational stacking pattern of parasequences 3 and fossil assemblage differs from the underlying unit with 4. Parasequences 1 to 3 correspond to shoreface facies and coquina layers by the scarcity of bivalves and abundance parasequence 4 to offshore transition facies representing of Eubaculites carinatus, with >90% of the total fauna. maximum water depths in the depositional area. Ammonites other than Eubaculites carinatus include Hypophylloceras. (Neophylloceras) ramosum, In consequence, parasequence 1 represents a Hypophylloceras. (Neophylloceras) inflatum, retrogradational facies pattern in a shoreface high energy Hypophylloceras. (Neophylloceras) hetonaiense, environment. This transgression resulted from sea level Kitchinites darwini, Maorites densicostatus, Menuites rise near the end of the Early Maastrichtian. Transgression gerardoi, Grossouvrites gemmatus, Grossouvrites joharae, continued through parasequences 2 to 3 which also reflect Anagaudryceras politissimum, Anagaudryceras shoreface facies (Figure 2), but with gradually decreasing subtilineatum, Phyllopachyceras forbesianum, energy levels. During parasequence 4, this Pachydiscus gutierrezi, Pachydiscus jacquoti, retrogradational system (transgression) continued in an Kossmaticeras erbeni, Kitchinites ifrimae, Baculites offshore transition environment with low energy levels. A huenickeni, Pseudophyllites indra, Zelandites varuna and strong regression ended marine sedimentation either near Gaudryceras kayei (Figure 1; Stinnesbeck 1986, 1996; the end of the Maastrichtian or cutting down from the Salazar et al. 2010). Sediments are mottled due to abundant Paleocene. The K/T boundary is thus incomplete due to trace fossils. Butois and Encinas (2011) recorded erosion and an extended hiatus. Teredolites isp. Thalassinoides isp. and Ophiomorpha isp. at Cocholgüe. Acknowledgements

In the uppermost 10 m of the unit with calcareous We are grateful to the Departamento Ciencias de la Tierra sandstone concretions Eubaculites carinatus is (Universidad de Concepción, Chile), for geological characteristically absent, but other ammonites still occur information and logistical support. We thank to Christina (Diplomoceras cylindraceum, Hypophylloceras. Ifrim for helpful comments on the manuscript. Financial

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support to this Project was given by the Deutsche Forschungsgemeinschaft (STI/128/6; STI/128/20) and BMBF project (CHL10/A09). References

Biro, L. 1982. Revisión y redefinición de los “Estratos de Quiriquina”, Campaniano-Maastrichtiano, en su localidad tipo en la Isla Quiriquina, 36º 35’ Lat. S, Chile, Sudamérica, con un perfil complementario en Cocholgüe. Actas III Congreso. Geológico Chileno. A 29-64. Concepción.

Buatois, L.; Encinas, A. 2011. Ichnology, sequence stratigraphy and depositional evolution of an Upper Cretaceous rocky shoreline in central Chile. Bioerosion structures in a transgressed metamorphic basement. Cretaceous Research. 32: 203-212.

Catuneanu, O. 2006. Principles of Sequence Stratigraphy. Elsevier Publishing Co. 375 p., Amsterdam, Boston, Heidelberg.

Coe, A.; Bosence, D.; Church, K.; Flint, S.; Howell, J.; Wilson, R. 2003. The Sedimentary Record of Sea-Level Change. Cambridge University Press. 287 p. Cambridge.

Francis, A.; Hallam, A. 2003. Ecology and evolution of trigoniid bivalves in Europe. Lethaia 36, 287-304.

Frutos, J.; Mencarini, P.; Pincheira, M.; Bourret, Y.; Alfaro, G. 1982. Geología de la Isla Quiriquina. Contribuciones del Departamento de Geociencias al III Congreso Geológico Chileno N°5: F 307-F 338. Concepción.

Nichols, G. 2009. Sedimentology and Stratigraphy, 2nd edition, Wiley Blackwell, 432 p. West Sussex.

Nielsen, S.; Salazar, C. 2011. Nautilus dorbignyanus Forbes, 1846 is an older synonym of N. subplicatus Steinmann, 1895 from the Quiriquina Formation (Cephalopoda; Maastrichtian, Chile). Cretaceous Research, 32: 833-840

Salazar, C.; Stinnesbeck, W.; Quinzio-Sinn, L.A. 2010. Ammonites from the Maastrichtian (Upper Cretaceous) Quiriquina Formation in central Chile. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 257/2, 181-236.

Stanley, S.M. 1977. Coadaptation in the Trigoniidae, a remarkable family of burrowing bivalves. Palaeontology 20 (4), 116-119.

Stinnesbeck, W. 1986. Zu den faunistischen und palökologischen Verhältnissen in der Quiriquina Formation (Maastrichtium) Zentral-Chiles. Palaeontographica, A194, 99- 237, plates 1-16.

Stinnesbeck, W. 1996. Ammonite extinction and environmental changes across the Cretaceous-Tertiary boundary in central Chile. 289-302. In McLeod, N. y Keller, G. (eds). Cretaceous- Tertiary Mass Extinctions: Biotic and Environmental Changes. Norton, New York, 575 pp.

Stinnesbeck, W.; Ifrim, C.; Salazar, C. 2012. The Last Cretaceous Ammonites in Latin America. Acta Palaeontologica Polonica. 57: 717 – 728.

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