Taphonomy and palaeoenvironmental interpretation of a new amber-bearing outcrop from the mid-Cretaceous of the Maestrazgo Basin (E Iberian Peninsula)

Abstract

Cretaceous amber-bearing outcrops are numerous and mainly distributed along the Northern Hemisphere. They have been related to extensive resin mass production occurring from the Barremian to the Campanian presumably due to interrelated abiotic and biotic factors. Amber outcrops are also abundant in the Iberian Peninsula, and they are mostly dated as Albian. Here, we present a new amber-bearing outcrop from the Cretaceous of the Maestrazgo Basin called La Dehesa (Estercuel, Aragón, Spain). This locality is assigned to the Boundary Marls Unit and is known for its rich and diverse palaeobotanical record. The dating of the amber-bearing bed is late Albian–early Cenomanian, based on palynomorphs and ostracods. Amber characteristics are compatible with a medium to long-distance transport before resin deposition, i.e., allochthonous origin. Organism-resin interactions have been identified, such as hyphae of resinicolous fungus in the cortex of the amber, a pholadid boring determined as Teredolites clavatus, and an oyster shell that grew on the solidified resin surface. No bioinclusions have been found so far. The study of the microfossils, some of them containing pyrite aggregates or crystals, found in the amber-bearing bed (palynomorphs, plant remains, foraminifers, echinoid spines, ostracods, and vertebrate remains) points to a coastal to inner mixed platform environment.