New insight on the age and significance of the Aparein black shales in the Basque-Cantabrian Basin, northern Spain

摘要

This paper re-interprets the ammonite record and carbon-isotope signals associated with the Aparein black shales (Lareo Formation) from the Sierra de Aralar Massif (Basque-Cantabrian Basin, northern Spain). An early late Aptian age (upper Epicheloniceras martini Zone) is re-assigned to the Aparein level. Its regional correlation is discussed. As herein suggested, the Aparein level is coeval to the Seberetxe level occurring in the Bilbao Formation from the nearby Bilbao area. The Aparein and Seberetxe levels are correlative to the Fallot black shales in the Blue Marls Formation of southeast France (Vocontian Basin), regarding both ammonite and carbon-isotope signal. The new age calibration will help in identifying the parameters that controlled organic matter enrichments in northern Spain and southeast France during the early late Aptian.