Hooked and tubular coralline algae indicate seagrass beds associated to Mediterranean Messinian reefs (Poniente Basin, Almería, SE Spain) Fernando Sola a , Juan C. Braga b, ⁎, Julio Aguirre b a Departamento de Hidrogeología, Universidad de Almería, 04120, Almería, Spain b Departamento de Estratigrafía y Paleontología, Universidad de Granada, Campus Fuentenueva, 18002, Granada, Spain abstract article info Article history: Received 25 July 2012 Received in revised form 21 January 2013 Accepted 22 January 2013 Available online 1 February 2013 Keywords: Coralline algae Seagrass beds Coral reefs Messinian Mediterranean Poniente Basin SE Spain Abundant hooked and tubular crustose coralline algae (CCA) record early Messinian (Late Miocene) seagrass beds on the northern margin of the Poniente Basin in southeastern Spain. Hooked and tubular shapes in CCA result from their epiphytic growth over seagrass leaves and stems. The lower Messinian deposits consist of a thin retrograding subunit overlain by sigmoidal bed packages that prograded to the southwest at least 650 m from the basin margin. Seagrass deposits mainly occur as bivalve/CCA packstone to rudstone and CCA floatstone, seawards of a conglomerate facies belt in the retrograding subunit and downslope of coral reefs and serpulid packstone to rudstone in the prograding sigmoidal beds. Fragments of contorted foliose CCA (“algal flakes”), some hooked or tubular, are common components in the seagrass deposits. They mainly be- long to an unidentified species of Mesophyllum. Like their present-day counterparts, the epiphytic CCA grew attached to seagrass by the initial parts of their thalli and displayed unattached projections or open frame- works of contorted foliose plants. In a few cases, hooked CCA occur attached to Halimeda plates. Small benthic foraminiferal assemblages are further evidence of macrophyte vegetation. Hooked contorted foliose CCA can be a helpful tool for the identification of ancient seagrass beds, especially in Mediterranean Neogene and Quaternary deposits, in which foraminiferal taxa fully indicative of seagrass ecosystems are scarce. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Seagrass beds cover extensive areas in present-day shallow-water environments in tropical to temperate seas (Hemminga and Duarte, 2000; Larkum et al., 2006). Epiphytic organisms and dwellers under the seagrass vegetation produce large amounts of calcium carbonate that can be significant in the sediment budget of certain depositional settings (Brasier, 1975; Nelsen and Ginsburg, 1986; Walker and Woelkerling, 1988). Dense seagrass meadows baffle currents, modify- ing the local hydrodynamic regime, and can trap and stabilize fine- grained sediment, partly produced in place, in turbulent shallow- water settings (Scoffin, 1970). The potential influence of seagrass in sedimentation extends back to its origin during the Late Cretaceous (Brasier, 1975; Van der Ham et al., 2007), but the presence of seagrass vegetation in the fossil record usually has to be inferred from indirect evidence as the preservation potential of seagrass plants is low and their fossils are therefore scarce (Lumbert et al., 1984; Moisette et al., 2007; Van der Ham et al., 2007). The abundance of certain foraminifers such as archaiasinids (Hottinger, 2001), ostracod assemblages (Cronin et al., 2001; Frenzel et al., 2005), and specific mollusc assemblages (Arroyo et al., 2006) can be reliable features for the recognition of an- cient seagrass beds. Other criteria, such as abundant echinoids, accumulations of peloids, abundance of constructive micrite envelopes (Perry, 1999), or the presence of unsorted muddy sediment inconsis- tent with surrounding higher-energy deposits can be arguable. Particu- larly in sub-tropical and temperate seas, dense seagrass beds might not promote the deposition of muddy sediment (Perry and Beavington- Penney, 2005). Beavington-Penney et al. (2004) proposed the occur- rence of crustose coralline algae (hereinafter CCA) with hooked morphologies as an additional criterion to recognize ancient seagrass ecosystems. Some CCA grow attached over the seagrass leaf margin, acquiring a hooked shape that cannot be generated in any other micro- habitat except on other macrophytes (such as macroalgae). Unfortu- nately, the most common and widespread CCA epiphytic on seagrass have very thin, weak thalli with low preservation potential: they decay producing fine-grained carbonate with no relics of their original growth form. Only the thickest thalli contribute to the sand-sized sedi- ment and can be recognized as fossils (Beavington-Penney et al., 2004). Despite this general situation, this study presents a case of wide- spread occurrence of hooked CCA associated with subtropical coral reefs in Messinian deposits in the western Mediterranean (Poniente Basin, SE Spain, Figs. 1 and 2). The hooked CCA plants, attached to seagrass, also developed contorted foliose branches, preserved as flake-like fragments in the sediment. These fragments are a conspicu- ous and easy indicator of ancient seagrass beds, which can be con- firmed by checking the presence of hooked and tubular thalli in hand samples or under the microscope. Although contorted foliose Palaeogeography, Palaeoclimatology, Palaeoecology 374 (2013) 218–229 ⁎ Corresponding author. Tel.: +34 958248332; fax: +34 958248528. E-mail address: jbraga@ugr.es (J.C. Braga). 0031-0182/$ – see front matter © 2013 Elsevier B.V. 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