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doi:10.2204/iodp.proc.342.201.2017

Results

The abundance and preservation of radiolarians in microfossil residues and the abundance of diatoms and radiolarians in smear slides is plotted for Sites U1403–U1410 in Figures F2, F3, F4, F5, F6, F7, F8, F9. These data are also recorded in Tables T1 and T2. The key features for each site are summarized below.

Site U1403

Site U1403 was drilled on the J-Anomaly Ridge in a water depth of 4946.5 m. It was the deepest site drilled during Expedition 342. A poorly dated upper Cenozoic sequence is underlain by a highly siliceous sequence of middle Eocene to Maastrichtian age (Fig. F2).

Radiolarians are abundant and well preserved in the middle Eocene and upper part of the lower Eocene (Cores 342-U1403A-9H through 17H; Zones RP13 through RP9). In the underlying lower Eocene and Paleocene interval (Cores 18X through 25X; Zones RP8 through RP6), radiolarian abundance fluctuates from few to abundant and preservation is moderate to poor. Radiolarians are rare but moderately preserved in the lower Paleocene–upper Maastrichtian interval (Cores 26X through 29X). Diatoms are not recorded in smear slides or microfossil residues from this site.

Site U1404

Site U1404 was drilled on the J-Anomaly Ridge in a water depth of 4746 m. The sediments comprise a condensed, poorly dated, upper Neogene interval underlain by an expanded interval of lower Miocene to middle Eocene drift sediments (Fig. F3).

Siliceous microfossils are abundant in two intervals in Hole U1404A: a lower Miocene to upper Oligocene interval (Cores 342-U1404A-3H through 19H; Zones RN2 through RP21), in which both radiolarians and diatoms are common to abundant, and a middle Eocene interval (Cores 28H through 36X [bottom of hole]; Zones RP16 through RP14), in which radiolarians are generally abundant but diatoms are absent. Significantly, siliceous microfossils are rare or absent through the Eocene–Oligocene transition at this site.

Site U1405

Site U1405 was drilled on J-Anomaly Ridge in a water depth of 4286 m. The sediments comprise a short upper Neogene interval underlain by a highly expanded succession of lower Miocene to upper Oligocene drift sediments (Fig. F4).

Siliceous microfossils are absent from the upper Neogene interval but are generally abundant to common and uniformly well preserved in the lower Miocene to upper Oligocene sediments (Cores 342-U1405A-4H through 29X; Zones RN4 through RP22). Radiolarians decrease in abundance in the lower part of the upper Oligocene interval (Cores 22H through 29X; Zone RP22) but remain well preserved. Diatoms are persistent in Cores 4H through 29X and peak in abundance through the Oligocene–Miocene transition (Cores 19H through 24H). Siliceous microfossils are rare or absent from the lower cores (Cores 30X through 33X).

Site U1406

Site U1406 was drilled on J-Anomaly Ridge in a water depth of 3814 m. It was the shallowest site drilled on J-Anomaly Ridge and recovered an expanded sequence of lower Miocene to middle to upper Eocene drift sediments, which are capped by a condensed sequence of Pliocene–Pleistocene sediments and underlain by Paleocene sediments (Fig. F5).

Siliceous microfossils are generally abundant and well preserved in three intervals within Hole U1406A: a lower Miocene to upper Oligocene interval (Cores 342-U1406A-2H through 15H; Zones RN3 through RP21a), a short middle Eocene interval (Core 29X; Zones RP11 through RP12), and a similarly short upper Paleocene interval (Core 31X; Zone RP7). Radiolarians dominate the siliceous microfossil assemblage, but diatoms are persistent, albeit rare, in both the upper and the Paleocene intervals. As at Site U1404, siliceous microfossils are absent from the Eocene–Oligocene transition interval (Cores 16H through 27X).

Site U1407

Site U1407 was drilled on the southeast Newfoundland ridge in a water depth of 3074 m. The sediments comprise a highly condensed Neogene and upper Paleogene succession underlain by a relatively expanded middle Eocene to upper Paleocene succession. The lower ~130 m of core is a condensed succession that extends from the lower Paleocene to the upper Albian (Fig. F6).

Siliceous microfossils are largely restricted to two intervals in Hole U1407A: a short lower Eocene interval (Cores 342-U1407A-10H through 11H; Zone RP11) and a relatively expanded upper Paleocene interval (Cores 16X through 22X; Zones RP7 through RP6a). Radiolarians are abundant and well preserved in these two intervals. Diatoms are rare in Hole U1407A and are restricted to these two intervals.

Site U1408

Site U1408 was drilled on southeast Newfoundland ridge in a water depth of 3022 m. It is the shallowest site drilled during this expedition. The sediments comprise a condensed Neogene and upper Paleogene succession underlain by middle Eocene drift sediments, which are in turn underlain by a relatively condensed succession of lower Eocene and upper Paleocene sediments (Fig. F7).

Siliceous microfossils are restricted to two short intervals in Hole U1408A. Abundant and well-preserved radiolarians occur in two cores within the expanded middle Eocene sequence (Cores 342-U1408A-16H and 17H; Zone RP13) and two cores in the uppermost Paleocene (Cores 26X and 27X; Zone RP7). Although not recorded in smear slides, radiolarians were also noted in microfossil assemblages directly above these two intervals, but preservation is too poor to confidently identify biostratigraphic marker species. Diatoms are rare in Hole U1408A sediments and are restricted to the two radiolarian-rich intervals.

Site U1409

Site U1409 was drilled on southeast Newfoundland ridge in a water depth of 3501.5 m. It is the deepest site drilled at this location. The sediments comprise a relatively condensed Neogene and upper Paleogene succession underlain by middle Eocene drift sediments, which are in turn underlain by a succession of lower Eocene and upper to middle Paleocene sediments (Fig. F8).

Diatoms and radiolarians are common in the uppermost two cores in Hole U1409A (342-U1409A-1H and 2H), which are of Pleistocene age. Deeper in Hole U1409A, siliceous microfossils are restricted to two intervals. Radiolarians are generally common and moderately well preserved in the lower Eocene (Cores 12H through 17X; Zones RP11 through RP8) and are abundant and well preserved in the uppermost Paleocene (Cores 20X and 21X; Zones RP7 and RP6c). Diatoms are rare in both intervals and absent from other pre-Pleistocene sediments in Hole U1409A.

Site U1410

Site U1410 was drilled on southeast Newfoundland ridge in a water depth of 3387 m. The sediments comprise a condensed Neogene and upper Paleogene succession underlain by middle to lower Eocene drift sediments (Fig. F9).

Diatoms and radiolarians are common in the uppermost two cores in Hole U1410A (342-U1410A-1H and 2H), which are of undifferentiated Pliocene–Pleistocene age. Deeper in Hole U1410A, siliceous microfossils are restricted to a single lower Eocene interval. Radiolarians are abundant and well preserved in Cores 23X through 26X and span the same Eocene radiolarian zones as in Hole U1409A: Zones RP11 through RP8. Diatoms are rare in this interval and absent from other pre-Pleistocene sediments in Hole U1410A.

Site U1411

Site U1411 was drilled on southeast Newfoundland ridge in a water depth of 3299 m. Siliceous microfossils are very rare and sporadically distributed at this site.

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