Palynomorphs were analyzed from 58 samples from ODP Leg 149 Hole 898A to establish an upper Cenozoic dinoflagellate cyst biostratigraphy for the Iberia Abyssal Plain. Five informal dinocyst biozones are defined based on the stratigraphic ranges of 75 dinocyst morphotypes identified from these sediments. These biozones are compared with dinocyst assemblages identified from a smaller number of samples (16) in Hole 900A, 43 km to the east at the base of the continental rise. A number of the dinocyst biozones defined in Hole 898A can be identified in sediments of equivalent age in Hole 900A, which differs mainly in the low numbers of protoperidinioid (congruentidioid) dinocysts and pollen. There are, however, significant differences between the Pliocene–Pleistocene sequences from these two sites, due to the abundant influx of terrigenous sediments to Site 898 with the beginning of turbidite sedimentation. Turbidite sediments can be identified palynologically by their ratio of marine palynomorphs (dinoflagellate cysts and acritarchs) vs. terrestrial palynomorphs (pollen and spores). This ratio (D:P) provides insight into the provenance of sediments on the Iberia Abyssal Plain while simultaneously providing paleoenvironmental information, allowing changes in depositional and erosional patterns in the eastern Iberia Abyssal Plain to be directly related to large-scale paleoclimatic and paleoceanographic changes in the temperate-subtropical eastern North Atlantic.

Date of initial receipt: 5 December 1994
Date of acceptance: 8 August 1995

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