Present-day temperate carbonate sedimentation on the Balearic Platform, western Mediterranean: compositional and textural variation along a low-energy isolated ramp

Abstract

The pre-1980s literature on modern carbonates was biased toward tropical examples because non-tropical carbonates had not been studied extensively. Though non-tropical carbonates have received considerable attention in the past decade, the variety of low-energy, temperate ramp examples in the literature is limited. In contrast, examples of modern and ancient low-energy, tropical ramps are well represented. They are characterized by a gradual change from calcarenites updip to calcilutites downdip, by a photozoan biota, abundant non-skeletal aragonitic grains, such as ooids and peloids, and by widespread and rapid marine cementation. The Balearic Platform in the western Mediterranean is an isolated, low-energy, temperate ramp. This paper describes the Balearic ramp bathymetry, environmental regimes and depositional facies, which include (from the shoreline seaward): coastal lagoons, beach—dune complexes, inner-ramp seagrass meadows with mixed terrigenous—foraminiferal—molluscan muddy calcarenites, middle-ramp bryozoan—rhodalgal facies and outer ramp clastic—carbonate muds. Biotic and textural characteristics vary with depth, with hydrological conditions and with environmental factors, such as temperature, salinity, light and nutrients. Seagrasses extend across the inner and part of the middle ramp, where the grasses offer shelter to a variety organisms, including epibionts, molluscs, bryozoans, echinoderms and red algae. Most of the beach and dune sediments consist of bioclasts derived from the communities that thrive in the seagrass meadows, but the greatest volume of skeletal carbonates is produced as bryozoan, rhodalgal and molluscan gravels that occur as patchy blankets, primarily on the middle ramp. The Balearic Platform is characterized by an oligotrophic, clear water, microtidal environment. The dominant biota of the Balearic ramp — bryozoans, red algae, echinoderms and molluscs — is common in other non-tropical modern environments as well as in ancient temperate settings. This fact, combined with the absence of aragonitic non-skeletal grains, abundant marine cements and photozoans other than red algae, establishes the modern Balearic ramp as a model for comparison with low-energy, non-tropical ramps in the global rock record.

Paleoecology and dynamics of coralline dominated facies during a Pleistocene transgressive–regressive cycle (Capo Colonna marine terrace, Southern Italy)

“…As documented in previous studies (Biagi and Corselli, 1978;Corselli, 1981;Fornos and Ahr, 1997), mollusk assemblages typical of coarse mobile bottom under moderate to high energy and connected to SGCF biocoenosis are reported for channels among Posidonia meadows. Posidonia meadows are also known to generate mud rich skeletal packstone (Pomar, 2001;Fornos and Ahr, 2006) similar to the bed in which the pralines were collected. It is therefore possible that the lower interval of the rhodolith bearing packstone records a spatially complex environment at the interface between Posidonia meadows and slightly deeper red algae dominated bottoms (Carannante et al, 1988;Canals and Ballesteros, 1997;Fornos and Ahr, 2006;Brandano and Civitelli, 2007).…”

Bryozoan Constructions in a Changing Mediterranean Sea

“…Cryptic microhabitats often shelter bryozoan-dominated assemblages containing numerous species (Harmelin 1985 ). Mediterranean bryozoan bioconstructions are usually characterized by encrusting multilaminar sheets which are able to form dome-like colonies, wrapping other organisms or inert substrates (Cigliano et al 2007 ;Cocito et al 2012 ;Kocak et al 2002 ;Poluzzi and Coppa 1991 ), and also by large erect arborescent colonies with multilaminar and/or robust branches (Cocito 2004 ;Cocito et al 2004 ;Lombardi et al 2008a ;McKinney and Jackson 1989 ;Novosel 2005 ) Strongly calcifi ed marine bryozoans are important producers of modern temperate carbonate sediment, both in the Mediterranean (Fornos and Ahr 2006 ;Bayhan et al 2001 ) and elsewhere (e.g. James and Bone 2010 ).…”

Controls on sediment dynamics and medium-term morphological change in a barred microtidal beach (Cala Millor, Mallorca, Western Mediterranean)

“…In contrast the Cala Millor study site corresponds to an individualized microtidal coastal cell where the fluvial component is weak. Permanent rivers are absent and continental sedimentation inputs are negligible (Fornós and Ahr, 2006). Additionally, regional studies of beach and shelf sediments highlight that the predominant biogenic sediment is derived from communities that thrive in the seagrass meadows of Posidonia oceanica (Alonso et al, 1988;Jaume and Fornós, 1992;Canals and Ballesteros, 1997;Fornós and Ahr, 1997) which are the main constituents (ca.…”

“…Therefore, disturbances related with new sedimentary budgets or with tides can be subtracted from morphological and sediment change co-variation analysis. Secondly, the minor presence of red algal and coralligenous bryozoans fragments, as well as of rhodolites (maërl), among dominant bulk components of foraminifera, echinoids and molluscs highlights a weak sediment intrabasinal contribution from benthic biota habitats between 20 and 50 m in depth (Fornós and Ahr, 2006). It is known from the analysis of 44 years of wave data to the beach that the waves necessary for carrying these coarse sediments inshore only have probabilities of occurrence during some winter gales .…”