MATERIAL AND METHODS

Hole 1082A is on the African continental slopes off Namibia (21°5.6373´S, 11°49.2361´E, 1279.3 m water depth). The lithologic composition is quite uniform throughout the 600.6 meters below seafloor (mbsf) hole, consisting largely of nannofossil-rich clay and nannofossil ooze (Shipboard Scientific Party, 1998). The middle part of the sequence (112-368 mbsf) is rather rich in diatoms. One sample per core was examined for a census of radiolarian assemblages.

Sample preparation for microscopic examination followed the standard techniques described by Sanfilippo et al. (1985). All samples were treated with hydrogen peroxide and hydrochloric acid and sieved at 63 µm and then briefly immersed in an ultrasonic bath and resieved. The cleaned residues were pipetted onto glass slides, dried without boiling, and mounted with Entellan-New alkylacrylate and coverslips. A minimum of 500 specimens of polycystine radiolarians were counted in each sample under a transmitted light microscope.

For each sample examined, qualitative estimates of radiolarian assemblage abundance and preservation were made (Table T1). Radiolarian assemblage abundance was assessed as follows:

A = abundant; >10,000 specimens on a slide.

C = common; 1001-10,000 specimens on a slide.

F = few; 501-1000 specimens on a slide.

R = rare; 11-500 specimens on a slide.

T = trace; 1-10 specimens on a slide.

B = barren; 0 specimens.

Preservation of the radiolarian assemblage was based on the following categories:

G = good; radiolarians show no signs of dissolution with only minor fragmentation.

M = moderate; radiolarians show evidence of moderate dissolution with obvious fragmentation.

P = poor; radiolarians show signs of a high degree of dissolution with very few intact specimens.

The following abbreviations are used in this study to express bioevents:

FO = first occurrence.

RI = rapid increase.

LCO = last common occurrence.

LO = last occurrence.

SA = short acme.