A complementary section for the proposed Toarcian (Lower Jurassic) global stratotype: The Almonacid de la Cuba section (Spain)

Abstract

Abstract-We present the biostratigraphy (ammonites, brachiopods, fo raminifers, and ostracodes), lithos tratigraphy, sedimentology, sequence stratigraphy, magnetostratigraphy, and isotope stratigraphy of the Almonacid de la Cuba section located in the Iberian Range, central-eastern Spain. This section, which con tains a continuous and expanded record of the Pliensbachian-To arcian boundary (Early Jurassic), has been proposed as a complementary section for the Toarcian GSSP. An excellent ammonite -based biozonation has been obtained. Four ammonite assemblages characterized by the presence of Pleuroceras, Canavaria, Dactylio ceras (Eodactylites ), and Dactylioceras (Orthodactylites) have been distinguished. The base of the To arcian is located at level eU35.2, based on the fi rst occurrence of Dactylioceras. The occurrence of taxa fr om the NW European and the Mediterranean provinces is useful to improve the correlation between both provinces. Fo r aminiferal and ostracode assemblages are rich and diversified and no significant biostratigraphic events take place at the Pliensbachian-To arcian boundary. The magnetostratigraphic data presented here are the most complete record of reversals of the earth magnetic fi eld for the Pliensbachian-To arcian boundary. A good record of the onset of the positive o13e excursion reported in the Lower To arcian of many European sections has been obtained. Ave rage paleotemperatures measured at the latest Pliensbachian Spinatum Biochron of about 12.5°e, recorded a marked increase of the seawater temperature which started durin� the To arcian , reaching average temperatures of 16.rC at the Te nuicostatum Biochron. The obtained 87 Sri 6 Sr va lues fully agree with the LOWESS calibration curve .

The base of the Toarcian (Early Jurassic) in the Almonacid de la Cuba section (Spain). Ammonite biostratigraphy, magnetostratigraphy and isotope stratigraphy

“…The Almonacid de la Cuba section, located in the Iberian Range of central-eastern Spain (Fig.1), shows a good representative record for the Pliensbachian-Toarcian boundary under outstanding outcrop conditions. The succession has been previously described by Sequeiros et al (1978), Comas-Rengifo (1982), Comas-Rengifo and Goy (l997), Comas-Rengifo et al (1999, 2010 and proposed as a complementary section of the Toarcian global stratotype (Goy et al, 2006).…”

“…A complex magnetization behaviour has been observed in the Almonacid de la Cuba section. Details of the palaeomagnetic study can be found in Palencia-Ortas (2004) and Comas-Rengifo et al (2010). Natural Remanent Magnetization (NRM) intensity ranged from 5 10 -3 A/m to 6 10 -5 A/m.…”

Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)

“…12). The Pliensbachian" Toarcian succession and the fossil content have been studied in detail (Goy et al, 2006;Comas-Rengifo et al, 2010 and references therein). The PLB/TOA boundary is recorded in the marlstone/limestone alternations of the Turmiel Fm, which was deposited in an open-marine, external platform environment (Gómez, 1991;Gómez and Goy, 2005).…”

Bouleiceras (Hildoceratidae, Ammonitina) from the lower Toarcian (Jurassic) of the Iberian Range (Spain): Taxonomy, stratigraphic distribution and insights on its dispersal

“…The succession of biohorizons (Figs. 2,3) corresponds to the regional data derived from Comas-Rengifo (1982) for the Pliensbachian and from Goy et al (1988), Martínez, 1990Goy andMartínez (1990), Comas-Rengifo et al (2010), as well as unpublished data, for the lower Toarcian. Figs.…”