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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.earscirev.2006.06.005 Byline: Federico Oloriz (a), Matias Reolid (a)(b), Francisco J. Rodriguez-Tovar (a) Keywords: micro- and macroinvertebrates; trophic relationships; paleoenvironmental features; epicontinental platform; Upper Jurassic Abstract: The palaeoenvironmental conditions and trophic structure of a mid-outer neritic biota (microfossils, mainly forams, and macroinvertebrate assemblages) have been approached in middle Oxfordian-lowermost Kimmeridgian deposits from the Prebetic Zone (Betic Cordillera) in south-eastern Spain. According to relationships between fossil assemblages and lithofacies, a general seaward trend is identified which displays decreasing sedimentation rates and nutrient inputs, but increasing substrate consistency and presumably depth. Midshelf, terrigenous-rich deposits in the External Prebetic relate to the highest sedimentation rates and nutrient availability. These two parameters correlate with the highest content in vagile-benthic, calcareous perforate, epifaunal forams, as well as with potentially deep infaunal forams and infaunal macroinvertebrates. Outer-shelf lumpy deposits in the Internal Prebetic show the lowest sedimentation rates and nutrient availability and the highest records for macro-micro nektonics and planktics. In contrast, vagile-benthic, calcareous perforate epifaunal and potentially deep infaunal forams are scarcer in the midshelf environments. Colonial encrusting forams, benthic microbial communities and sessile benthic macro-invertebrates increase from the middle to outer shelf. Trophic-analysis structuring through the integration of benthic microbial communities, foraminiferal and macroinvertebrate fossil assemblages makes it possible to interpret: (a) a trophic-level frame composed of producers and primary and secondary consumers; (b) a main trophic-group differentiation in suspension-feeders, detritus-feeders, browsers, grazers, carnivores and scavengers; (c) a preliminary approach to food-chain structure supported by suspension-feeders, deposit-feeders and predators (active prey-selection carnivores); and (d) a food-pyramid model, which takes into account both recorded fossils and envisaged -- i.e., ecologically inferred-organisms. Author Affiliation: (a) Departamento de Estratigrafia y Paleontologia, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18071 Granada, Spain (b) UMR 5125, Paleoenvironnements and Paleobiosphere, Universite Claude Bernard Lyon-1, 2 rue Raphael Dubois, BAcentst. Geode, F-69622 Villeurbanne Cedex, France Article History: Received 5 August 2005; Accepted 15 June 2006

The palaeoenvironmental conditions and trophic structure of a mid-outer neritic biota (microfossils, mainly forams, and macroinvertebrate assemblages) have been approached in middle Oxfordian--lowermost Kimmeridgian deposits from the Prebetic Zone (Betic Cordillera) in south-eastern Spain. According to relationships between fossil assemblages and lithofacies, a general seaward trend is identified which displays decreasing sedimentation rates and nutrient inputs, but increasing substrate consistency and presumably depth. Midshelf, terrigenous-rich deposits in the External Prebetic relate to the highest sedimentation rates and nutrient availability. These two parameters correlate with the highest content in vagile-benthic, calcareous perforate, epifaunal forams, as well as with potentially deep infaunal forams and infaunal macroinvertebrates. Outer-shelf lumpy deposits in the Internal Prebetic show the lowest sedimentation rates and nutrient availability and the highest records for macro-micro nektonics and planktics. In contrast, vagile-benthic, calcareous perforate epifaunal and potentially deep infaunal forams are scarcer in the midshelf environments. Colonial encrusting forams, benthic microbial communities and sessile benthic macro-invertebrates increase from the middle to outer shelf. Trophic-analysis structuring through the integration of benthic microbial communities, foraminiferal and macroinvertebrate fossil assemblages makes it possible to interpret: (a) a trophic-level flame composed of producers and primary and secondary consumers; (b) a main trophic-group differentiation in suspension-feeders, detritus-feeders, browsers, grazers, carnivores and scavengers; (c) a preliminary approach to food-chain structure supported by suspension-feeders, deposit-feeders and predators (active prey-selection carnivores); and (d) a food-pyramid model, which takes into account both recorded fossils and envisaged--i.e., ecologically inferred-organisms. Keywords: micro- and macroinvertebrates; trophic relationships; paleoenvironmental features; epicontinental platform; Upper Jurassic

A detailed ichnological analysis focused on Thalassinoides structures recorded just below the Cretaceous-Paleogene (K-P) boundary layer of the Agost section (southeast Spain) aimed to evaluate macrobenthic colonization during the K-P boundary event. Stereomicroscopy and field emission scanning electron microscopy analyses conducted on material filling in Thalassinoides trace fossils reveal the presence of dark infill material that includes spherule-like elements, similar to those previously differentiated in the K-P boundary layer. Energy-dispersive X-ray spectrometry indicates a ferruginous composition (goethite spherules). This represents the first record of spherules related to the K-P boundary event within trace-fossil infilling material. The passive filling of this material into the Thalassinoides bioturbation allows interpretation of the gravitational deposition just after Thalassinoides trace-maker colonization. The absence of erosive sedimentary structures or other material deposited between the Thalassinoides trace-maker colonization and the spherule deposition is interpreted as evidence of rapid colonization during the K-P boundary event, nearly contemporary with the spherule layer deposition. Keywords: Cretaceous-Paleogene boundary event, Thalassinoides, Fe-oxide spherules, macrobenthic colonization.

Palaeogene trace fossils penetrate the uppermost Cretaceous sediments in the Agost section, Betic Cordillera, SE Spain. Chondrites ?targionii, Zoophycos isp., Planolites isp. A, Planolites isp. B, ?Thalassinoides isp. A, Thalassinoides isp. B, Thalassinoides isp. C, Alcyonidiopsis longobardiae, and Diplocraterion ?parallelum have been identified. A well-developed endobenthic tiering pattern is interpreted. The uppermost tier (A) represents major benthic activity in the shallowest sediments at or just below the seafloor, recorded as bioturbated background (only discrete rare Planolites). The next upper tier (B) displays the highest trace-fossil diversity, with Planolites in the shallow levels, and Thalassinoides and Alcyonidiopsis at slightly deeper ones. The intermediate tier (C) contains randomly distributed Thalassinoides and Alcyonidiopsis, cross-cut by Zoophycos and large and medium-sized Chondrites. The deepest tier (D) contains Zoophycos, cross-cut by medium- and mainly small-sized Chondrites. Two interpretations are proposed: (1) vertical partitioning of a singled multi-tiered community under steady-stable conditions in well-oxygenated water bottom, reflecting gradual changes deep into the sediment, with decreasing oxygen pore water and benthic food, and increasing substrate consistency, and (2) sequential colonization and community replacement, reflecting the work of two successive communities. The first community, mainly represented by Planolites, Alcyonidiopsis and Thalassinoides, was produced in a shallow, oxygenated soft substrate. Probably related to decreasing oxygen content and benthic food availability, this community was replaced by deeply burrowing organisms that produced Zoophycos and Chondrites. This sequential colonization can be determined by changes in environmental parameters related to the Cretaceous-Palaeogene (K-T) event, or may have resulted from normal ecological and early diagenetic processes. Keywords: Cretaceous-Tertiary boundary, trace fossil, palaeoenvironmental change, Spain.