19. ⁴⁰Ar/³⁹Ar AGES OF PLIOCENE–PLEISTOCENE FALLOUT TEPHRA LAYERS AND VOLCANICLASTIC DEPOSITS IN THE SEDIMENTARY APRONS OF GRAN CANARIA AND TENERIFE (SITES 953, 954, AND 956)¹

Paul van den Bogaard ²

ABSTRACT

Six fallout tephra layers and 16 heterolithologic volcaniclastic deposits drilled at Holes 953A, 954A, 954B, and 956A, during Leg 157 in the sedimentary aprons of Gran Canaria and Tenerife, have been dated by single crystal laser ⁴⁰Ar/³⁹Ar analysis. The fallout tephra markers range in age from 0.273 ± 0.006 Ma to 2.74 ± 0.01 Ma. Maximum sedimentation ages determined for the volcaniclastic deposits range from 0.24 ± 0.01 Ma to 2.24 ± 0.02 Ma, closely matching the nannofossil and paleomagnetic chronostratigraphies of the cores. Both tephra and volcaniclastic layers represent material from Pliocene–Pleistocene explosive eruptions of the Cañadas Caldera (Tenerife), mixed with Miocene volcanic debris only in the holes drilled north of Gran Canaria (954A and 954B). Two fallout layers (0.61 ± 0.02 Ma and 1.83 ± 0.02 Ma) and five volcaniclastic deposits reflect explosive eruptions, which took place during postulated dormant stages of the Cañadas edifice.

¹ Weaver, P.P.E., Schmincke, H.-U., Firth, J.V., and Duffield, W. (Eds.), 1998. Proc. ODP, Sci. Results, 157: College Station, TX (Ocean Drilling Program).
² GEOMAR Forschungszentrum, Wischhofstrasse 1-3, D-24148 Kiel, Federal Republic of Germany. pbogaard@geomar.de