Unusual concentration of Early Albian arthropod-bearing amber in the Basque-Cantabrian Basin (El Soplao, Cantabria, Northern Spain): Palaeoenvironmental and palaeobiological implications

• Published in: Geologica acta Vol. 7; no. 3; pp. 363 - 387
• Main Authors: Najarro, M, Pérez-De la fuente, R, Rosales, I, Daviero-Gómez, V, Peñalver, E
• Format: Journal Article
• Language: English
• Published: Institut de Ciències de la Terra "Jaume Almera" 2009
• Subjects: Arthropod bioinclusions; Fossil resin; Lower Albian; Plant cuticles; Spain
• ISSN: 1695-6133; 1696-5728
• DOI: 10.1344/105.000001443

The El Soplao site is a recently-discovered Early Albian locality of the Basque-Cantabrian Basin (northern
Spain) that has yielded a number of amber pieces with abundant bioinclusions. The amber-bearing deposit
occurs in a non-marine to transitional marine siliciclastic unit (Las Peñosas Formation) that is interleaved within
a regressive-transgressive, carbonate-dominated Lower Aptian-Upper Albian marine sequence. The Las
Peñosas Formation corresponds to the regressive stage of this sequence and in its turn it splits into two smaller
regressive-transgressive cycles. The coal and amber-bearing deposits occur in deltaic-estuarine environments
developed during the maximum regressive episodes of these smaller regressive-transgressive cycles. The El
Soplao amber shows Fourier Transform Infrared Spectroscopy spectra similar to other Spanish Cretaceous
ambers and it is characterized by the profusion of sub-aerial, stalactite-like flows. Well-preserved plant cuticles
assigned to the conifer genera Frenelopsis and Mirovia are abundant in the beds associated with amber. Leaves
of the ginkgoalean genera Nehvizdya and Pseudotorellia also occur occasionally. Bioinclusions mainly consist
of fossil insects of the orders Blattaria, Hemiptera, Thysanoptera, Raphidioptera, Neuroptera, Coleoptera,
Hymenoptera and Diptera, although some spiders and spider webs have been observed as well. Some insects
belong to groups scarce in the fossil record, such as a new morphotype of the wasp Archaeromma (of the family
Mymarommatidae) and the biting midge Lebanoculicoides (of the monogeneric subfamily Lebanoculicoidinae).
This new amber locality constitutes a very significant finding that will contribute to improving the knowledge
and comprehension of the Albian non-marine paleoarthropod fauna.