Preliminary taphonomic approach to “Lo Hueco” palaeontological site (Upper Cretaceous, Cuenca, Spain)

“Lo Hueco” encloses an extraordinary upper Campanian-lower Maastrichtian fossil assemblage, composed mainly of vertebrates but also plants and invertebrates, and concentrated in a sandy channel structure (C), two grey marly mudstone levels (G1 and G2) and the lower part of a red marly mudstone level (R2). Regarding biostratinomy, the C structure (interpreted as a distributary sandy channel) contains numerous highly altered and randomly distributed macrofossils. The G1 level (the proximal part of a flooded muddy plain) preserves several totally or partially articulated specimens, mainly sauropods, with low degree of scattering and preferred orientation with respect to C. The G2 level (the distal part of a flooded muddy plain) and the lower part of the R2 level (the dried part of a muddy plain) contain numerous rarely articulated and randomly scattered macrofossils. Concerning fossil diagenesis, macroscopically, most bones present a first infilling of gypsum in spongy cavities, a ferruginous crust over outer surfaces and a second precipitation of gypsum over outer surfaces and eventually crossing the ferruginous crust and the first infilling of gypsum. Microscopically, most bones from the C structure and the G1 level additionally show radial microcracks in secondary osteons and ferruginous rings in Haversian channels. Given their particular geological and taphonomic characteristics, the C structure, the G1 and G2 levels and the lower part of the R2 level constitute four distinct taphofacies or bonebeds.