Systematics and Distribution of Decapod Crustaceans Associated with Late Eocene Coral Buildups from the Southern Pyrenees (Spain)
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N. Jb. Geol. Paläont. Abh. 296/1–2 (2020), 79–100 Article Stuttgart, May 2020 Systematics and distribution of decapod crustaceans associated with late Eocene coral buildups from the southern Pyrenees (Spain) Fernando A. Ferratges, Samuel Zamora, and Marcos Aurell With 9 figures and 3 tables Abstract: A new decapod crustacean assemblage associated with late Eocene coral reef deposits in northeast Spain (southern Pyrenees) is recorded; it includes Gemmellarocarcinus riglosensis sp. nov., Daira corallina sp. nov., Lobogalenopsis joei sp. nov., Liopsalis cf. anodon (Bittner, 1875) and Gale nopsis crassifrons A. Milne-Edwards, 1865. The genera Gemmellarocarcinus, Daira and Lobogale nopsis are here recorded for the first time from Eocene strata of the Iberian Peninsula, extending their palaeobiogeographical distribution. Detailed sampling from three different coral reef facies within the La Peña buildup, here referred to as branching, tabular and massive, suggest that the core of the reef, which was dominated by branching corals, hosted the highest diversity and abundance of decapod crustaceans. Daira corallina sp. nov. predominated in the branching corals facies, while G. crassi forns was the most abundant taxon within the tabular coral facies and carpiliids showed preferences for environments with massive corals. Thus, this constitutes a good example of primary ecological zonation among decapod crustaceans within a discrete reef. This paper is part of the special volume: Jagt, J.W.M., Fraaije, R.H.B., Van Bakel, B.W.M., Don- ovan, S.K., Mellish, C. & Schweigert, G. (eds.): A lifetime amongst fossil crustaceans: a tribute to Joseph S.H. Collins (1927–2019). Key words: Crustacea, Brachyura, coral-associated crabs, taxonomy, Paleogene, cryptofauna. 1. Introduction 2017), hosting decapod crustacean communities with taxa that are similar to those that inhabit modern reefs The Eocene Epoch was crucial in the development of (Müller & Collins 1991; De Angeli & Garassino many present- day features of the Earth. In particular, 2002; Busulini et al. 2006; Beschin et al. 2007; Tes- new palaeogeographical configurations and ocean sier et al. 2011; Beschin et al. 2012, De Angeli & circulation patterns forced by tectonic plate rear- Ceccon 2012; De Angeli & Ceccon 2013a, De An- rangement, led to the initial development of Antarc- geli & Ceccon 2013b; De Angeli & Ceccon 2014; tic ice sheets during the late Eocene and a progressive De Angeli & Garassino 2014; Beschin et al. 2015; switch from greenhouse to icehouse climatic condi- De Angeli & Ceccon 2015; Beschin et al. 2016; tions (e.g., Hallock et al. 1991; Hallock & Pomar De Angeli & Ceccon 2016; Beschin et al. 2017). The 2008; Stickley et al. 2009). These climatic changes Eocene is also considered an important period in the had an impact on the evolution of reefs and associat- evolution of brachyurans (e.g., Fraaije 2003; Brösing ed metazoan communities (Pomar et al. 2017). Coral 2008; Tsang et al. 2014; Schweitzer & Feldmann reefs were fully established in this period (Pomar et al. 2015). Despite a good understanding of the taxonomic © 2020 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany www.schweizerbart.de DOI: 10.1127/njgpa/2020/0893 0077-7749/2020/0893 $ 5.50 80 F.A. Ferratges et al. Fig. 1. Mid- Eocene palaeogeographical map of the Pyrenean area, showing the location of the Jaca-Pamplona Basin (mod- ified from Silva-Casal et al. 2017). The squared area in the southern part is enlarged in Fig. 2. composition of decapod assemblages associated with terials and methods’ below). The aim of the present reef environments during the Eocene, little is known study is to describe all material collected and discuss about how these faunal assemblages are distributed at the presence of certain taxa in different parts of the outcrop level. In contrast, other periods have been fur- reef. ther investigated in this respect and some palaeoeco- logical studies have been published for the Cretaceous (Klompmaker et al. 2013), Paleocene (Klompmaker et al. 2016) and the modern day (Abele 1979). 2. Geological setting Outcrops located in the central part of the southern Pyrenees include an extraordinary record of middle– The southern Pyrenean basins record one of the most upper Eocene rocks with coral buildups and associated complete Eocene marine sedimentary successions in benthic faunas at several time intervals (Puigdefab- Europe, with decapod crustaceans previously described regas 1975; Millán et al. 1994; Pomar et al. 2017). from several outcrops (see e.g., Vía 1969; Vía- Boada Upper Eocene reefs are well represented in the upper 1973; Artal & Vía 1988; Artal & Castillo 2005; Ar- portion of the Arguis- Pamplona Marls Formation, tal et al. 2013; Ossó et al. 2014; Domínguez & Ossó along the southern margin of the Jaca- Pamplona Ba- 2016; López- Horgue & Bodego 2017; Ossó & Domín- sin (Fig. 1). The upper part of the prodeltaic, clay- guez 2017; Artal & Van Bakel 2018a; Artal & Van dominated succession represented by the Arguis For- Bakel 2018b; Ferratges et al. 2019). Palaeogeographi- mation includes levels with early Priabonian (latest cally, the southern Pyrenean basin was located at approx- Eocene) mesophotic coral buildups. These buildups, imately 35ºN palaeolatitude during the Eocene (e.g., Hay between the localities of Rasal and La Peña (province et al. 1999; Silva-Casal et al. 2017) and corresponded to of Huesca, northern Spain), were characterised by an elongated gulf connected towards the west by the Bay Morsilli et al. (2012). In order to understand deca- of Biscay, located on the southern limit of the axial zone pod crustacean composition and their distribution in of the Pyrenees. The gulf was flanked by shallow-water these lower Priabonian reefs, detailed sampling in the carbonate platforms, with accumulations of hemipelagic La Peña reef was carried out. Specimens were collect- sediments at the bottom of the basin (Fig. 1). ed in association with specific microfacies (see ‘Ma- Systematics and distribution of decapod crustaceans 81 The Jaca- Pamplona Basin corresponds to an elon- that yields abundant benthic fossils. The lateral extent gated basin from east to west in the south- central of the shallow-marine units overlying the relatively Pyrenean Zone (Fig. 1). This basin was formed as a deep marly facies is progressively larger in younger result of the southward propagation of the tectonic sequences, with progradation advancing from east to structures during the Paleogene (Millán et al. 1994; west. Siliciclastic components also increase according Muñoz et al. 1994; Castelltort et al. 2003; Huyghe to the same pattern and they become clearly dominant et al. 2009). The propagation of the southern Pyrenean in the uppermost depositional sequence (Fig. 2A). fold and thrust belt resulted in the formation of a co- Specifically, the decapod crustaceans studied for eval relief, acting as a sediment source area for delta- the present paper come from lower Priabonian coral ic complexes (e.g., Dreyer et al. 1999). These deltaic buildups developed in the middle part of Sequence IV. complexes prograded westwards in the southern part These buildups form discontinuous outcrops between of the Jaca- Pamplona Basin, progressively covering the localities of Rasal and La Peña (Fig. 2B). These the turbiditic systems of the lower and middle Eocene coral buildups provided a good opportunity for other of the Hecho Group (Mutti et al. 1985; Remacha et al. invertebrates to colonise such a specific environment 2003; Remacha et al. 2005). (e.g., echinoderms, molluscs, decapod crustaceans The Sierras Exteriores includes outcrops located etc). Although several outcrops have been sampled along the southern margin of the Jaca- Pamplona Basin for decapod crustaceans, only the one located east of (Fig. 2A). The middle and upper Eocene (Lutetian– La Peña provided fresh rock and enough material to be Priabonian) units form a c. 2-km- thick succession, in- analysed in detail. cluding shallow-marine limestones of the Guara For- mation, the prodelta/outer ramp marls/clays of the Ar- guis Formation, the deltaic Belsue- Atares Formation and its lateral counterpart (i.e., coastal siliciclastics of 3. The early Priabonian coral reefs of La Peña the Yeste- Arres Formation) and the fluvial Campodar- be Formation (Puigdefabregas 1975; Silva- Casal An integrative analysis of rock textures, skeletal com- et al. 2019). These units are diachronous and record ponents, buildup anatomy and facies architecture has the late-stage infilling of the foreland basin (Millán revealed that the early Priabonian coral buildups ex- et al. 1994; Millán et al. 2000). Coeval to basin in- posed between the localities of La Peña and Rasal fill, a series of thrust ramps and oblique folds with a (Fig. 2B) developed in a prodelta setting (Morsilli north- south axis started to develop during the Lute- et al. 2012). There, shifting of delta lobes episodically tian and progressively propagated westwards until the resulted in periods of water transparency that allowed Bartonian to early Priabonian with variable shortening zooxanthellate coral growth. A bathymetric posi- rates (Millán et al. 1994; Castelltort et al. 2003; tion of the buildups around 15–25 m was constrained Huyghe et al. 2009). The uppermost Lutetian–lower by Morsilli et al. (2012) from the analysis of light- Priabonian sedimentary units coevally deposited with dependent communities and lithofacies distribution these growth structures are arranged in four Deposi- within the buildups. Most