Abstract:
Turbidite deposition in the mid-plate, hot-spot setting of the Canary Islands is controlled not only by local volcanism, but by sea level fluctuations and regional climate. We examined 25 turbidites from the Late Miocene to the Quaternary at ODP Site 953, which lies on the northeast edge of the volcanic apron of Gran Canaria at 3485 m in a small basin that is sheltered from turbidite input from the nearby Moroccan continental margin. The site is composed of volcaniclastic and biogenic carbonate turbidites interlayered with pelagic sequences that provide excellent age control.Benthonic foraminifers were identified and assigned to depth zones according to their depth preferences on the northwest African continental margin. All turbidites contain a mixture of specimens from neritic, upper, middle, and lower bathyal, and abyssal depth zones. Late Miocene and Early Pliocene turbidites are dominated by an upper bathyal assemblage from 130 to 1000 m water depth. Late Pliocene and Quaternary volcaniclastic-rich turbidites are also dominated by an upper bathyal assemblage, but the species composition is different. The younger turbidite sequence bears another significant difference. Thick biogenic carbonate turbidites composed of neritic fossils first appear at about 3 Ma and become common in the Quaternary interval. The changes in turbidite faunas between the Early and Late Pliocene are connected to environmental changes brought on by global cooling beginning 2.8 Ma. Effects include altered bathyal-depth water properties and structure that affect bathyal assemblages; increased aridity reducing clastic sediment supply to the island shelf; and increased sea level fluctuations, which caused sediment starvation on the shelf during highstands when temperate carbonate producers flourished.