IODP Expedition 342:
Paleogene Newfoundland Sediment Drifts
Site U1410 Summary
PDF file is available for download.
Background and objectives
U1410 (proposed site SENR-23A; 41° 19.6993'N, 49° 10.1847'W) is a mid-depth
site (~3400 m; ~2950 m paleodepth at 50 Ma, Tucholke and Vogt, 1979), in the
upper mid-depth end of the Expedition 342 Paleogene Newfoundland Sediment
Drifts depth transect. The site is positioned to capture a record of
sedimentation around 1.5 km shallower than the largely sub-carbonate
compensation depth record drilled at IODP Site U1403. The location, well above
the average late Paleogene carbonate compensation depth (CCD), should be
sensitive to both increases and decreases in carbonate burial, whether these
reflect variations in dissolution related to changes in the CCD, changes in
carbonate production, or variations in background non-carbonate sedimentation.
Our primary scientific objectives for drilling Site U1410 were (1) to obtain an
expanded record of lower to middle Eocene drift sedimentation to compare directly
to the relatively condensed record at Site U1409 drilled on the edge of the
same drift; (2) capture fine-scale variations in carbonate preservation and
lysocline shifts in carbonate-rich sediments that are about 400 m deeper than
Site U1408; and (3) to evaluate the history of deep water and the carbonate
compensation depth on sediment chemistry, grain-size and provenance. Secondary
objectives included the possible recovery of specific Paleogene hyperthermals
such as the Middle Eocene Climatic Optimum (MECO) for comparison with the
record of these events elsewhere, particularly Sites U1404, U1406 and U1408
along the Expedition 342 depth transect.
vessel arrived at Site U1410 (proposed site SENR-23A) at 1845 h (UTC-2.5h) on
20 July 2012, after a 3.46 nmi transit from Site U1409 in dynamic positioning
mode that took 3.5 hours at 1.0 nmi/hr. The plan for
Site U1410 called for three holes to a depth of ~250 m drilling depth below seafloor
(DSF). Hole U1410A (3387.3 m water depth) was spudded at 2125 h on 20 July.
Cores U1410A-1H through 16H were recovered to 151.0 m DSF using non-magnetic
core barrels and the FLEXIT core orientation tool. Core U1410A-16H experienced
the first partial stroke. The XCB system was deployed for Cores U1410A-17X
through 28X to the final depth of 259.8 m DSF. The seafloor was cleared at 0500
h on 22 July, ending Hole U1410A. Overall core recovery for Hole U1410A was
256.88 m for the 259.8 m interval cored (99%). The total time spent on Hole
U1410A was 34.25 hours.
vessel was offset 20 m to the east. Hole U1410B (3398.7 m water depth) was
spudded at 0650 h on 22 July. Cores U1410B-1H through 18H were recovered to
153.8 m DSF using non-magnetic core barrels and the FLEXIT core orientation
tool. The XCB system was deployed for Cores U1410B-19X through 28X to the final
depth of 245.2 m DSF. The seafloor was cleared at 1620 h on 23 July, ending
Hole U1410B. The recovery for Hole U1410B was 244.84 m over the 245.2 m cored (100%).
The total time spent on Hole U1410B was 35.25 hours.
vessel was offset 20 m to the south and Hole U1410C (3386.9 m water depth) was
spudded at 1825 h on 23 July. Cores U1410C-1H through 16H were recovered to
146.8 m DSF using non-magnetic core barrels. No core orientation was performed
on Hole U1410C. The XCB system was deployed for Cores U1410C-17X through 27X to
the final depth of 243.8 m DSF. The recovery for Hole U1410C was 238.81 m over
the 243.8 m cored (98%). The recovery for Site U1410 was 740.5 m out of 748.8 m
cored (98%). The seafloor was cleared and the vessel was secured for transit at
0915 h on 25 July, ending Hole U1410C. The total time spent on Hole U1410C was
sedimentary sequence at Site U1410 comprises four lithostratigraphic units.
Unit I is a ~34 m thick succession of Pleistocene sediments with alternating
reddish brown clay, gray to dark brown muddy/clayey foraminiferal ooze with
nannofossils, grayish brown foraminiferal sand, and occasional sand- to pebble-sized
lithic grains. Unit II is a ~30 m thick succession of clay, clay with
nannofossils, and nannofossil clay of late Miocene to Oligocene age. Manganese,
present as discrete nodules or disseminated silt- to sand-sized flecks, and
disseminated sulfides are common. Sedimentological and biostratigraphic
information indicate that Unit II contains multiple hiatal surfaces in addition
to the unconformities that define its upper and lower boundaries. Middle to
Early Eocene Unit III is the thickest of the four units (ranging from 63 to 68
m thick) and contains greenish gray nannofossil clay and greenish nannofossil
clay to clayey nannofossil ooze with distinctive 10-25 cm thick bands of light
gray to white nannofossil ooze that occur as a secondary lithology. Lithostratigraphic
Unit IV is a 48 m thick sequence of white to pinkish white nannofossil chalk
with foraminifers and/or radiolarians of Middle Eocene to Early Eocene age.
This unit is subdivided into two generally similar subunits, with the lower
subunit containing several chert beds.
planktic foraminifers and benthic foraminifers are present through most of the
Pleistocene to lower Eocene succession. Short barren intervals occur between
thin Pleistocene, upper Miocene and lower Miocene/Oligocene sequences.
Radiolarians are only present in the uppermost Pleistocene and lower Eocene.
Thin Pleistocene, upper Miocene and lower Miocene/Oligocene sequences overlie a
middle Eocene through lower Eocene succession. Hiatuses or highly condensed
intervals occur between the lower Pleistocene and upper Miocene (7.1 my
duration), upper and lower Miocene (7.4 my duration), lower Miocene and upper
Oligocene (5.4 my duration), and lower Oligocene and middle Eocene (7.4 my
duration). The Oligocene is highly condensed and may also contain significant
results reveal two series of normal and reverse magnetozones. The first zone is
observed between Cores U1410A-1H and 4H (~0-33 m core depth below seafloor
[CSF-A]), between Cores U1410B-1H and 5H (~0-33 m CSF-A), and between Cores
U1410C-1H and 4H (~0-32 m CSF-A). The second series is observed between Cores
U1410A-8H and 24X (~69-218 m CSF-A), between Cores U1410B-9H and 15H (~69-121 m
CSF-A), and between Cores U1410C-8H and 14H (~70-118 m CSF-A). These
magnetostratigraphies are straightforward to correlate among all three holes and represent two
distinct time intervals. The first interval is from Chron C1n (Brunhes, Modern)
through upper Chron C2An.1n (Gauss, ~2.6 Ma); the second interval is from upper
Chron C18n.1n (~39.6 Ma) through upper Chron C21r (~47.4 Ma). The lower part of
Chron C20n, as well as Chrons C21n and C21r, have
not yet been correlated in the XCB recovered intervals in Holes U1410B and
U1410C. Finally, the geomagnetic field transitions from C18n.1n to C18n.1r to
C18n.2n are recorded in exceptional detail in Hole U1410B, and show remarkably
similar behavior as the same transitions recorded at Site U1408.
magnetochronology and biochronology suggests that average linear sedimentation
rates (LSRs) were ~1.5-2.3 cm/ky during the Pleistocene, with higher
sedimentation rates during Chron C2 than during Chron C1. Sedimentation rates
are 0.2 cm/ky through the Oligocene. Average LSRs varied from 1.30 cm/ky at the
beginning of the Middle Eocene to 1.98 cm/ky at the end of the Middle Eocene.
Within the Middle Eocene, LSRs peak at 2.63 cm/ky during Chron C20n, one chron
younger than the interval of peak LSRs at Site U1409. Finally, biochronology
suggests sedimentation rates of 0.6 cm/ky through the lower Eocene.
stratigraphic splice constructed for Site U1410 is continuous from 0 to ~256 m core
composite depth below seafloor (CCSF), with the exception of one append at ~226
m CCSF. Correlation during drilling operations was possible because of clear,
correlative signals in magnetic susceptibility. Magnetic susceptibility and
natural gamma radiation (NGR) were used for refining the real-time correlation
and constructing the splice. All three holes recorded the prominent
lithological transition from greenish clay to carbonate-rich sediments,
characterized by a step change to lower magnetic susceptibility and NGR at ~220
to 230 m CCSF (across the early-middle Eocene). Core U1410A-23X, showing the
transitional physical properties data, shows clear green to white cycles, which
are absent from the equivalent cores in Holes U1410B and U1410C. As a result,
we append Core U1410A-23X in the splice and add large offsets to Cores
U1410B-26X and U1410C-24X (13.3 and 4.8 m, respectively).
methane concentrations (2.11–6.72 ppmv) were not above atmospheric
levels. Interstitial pore water profiles display evidence of
compartmentalization with prominent abrupt downhole shifts in magnesium,
manganese, and potassium at ~220-230 m CSF-A suggesting that the unrecovered
sequence of cherts functions as an aquiclude. Overall, interstitial pore water
profiles of potassium, calcium, and magnesium are consistent with those
resulting from exchange with and alteration of basaltic basement at depth.
Potassium and magnesium concentrations decrease and calcium concentrations
increase with depth. The downhole patterns of manganese, iron and sulfate
suggest organic matter degradation. Low alkalinity, ammonium and manganese
concentrations and high sulfate concentrations suggests that the influence of
organic matter respiration within the sediment column at Site U1410 is modest.
The broad downhole peak in boron concentrations at ~30 m CSF-A presumably
indicates increased supply from the terrigenous sediment component in
lithostratigraphic Unit II.
content in the entire sediment column at Site U1409 ranges from 0.7 to 92%. As observed
at our other drill sites on the Southeast Newfoundland Ridge (Sites
U1407-U1409), the most prominent change is a step increase (46 to 52 wt% CaCO3,
~210 m CSF-A) in calcium carbonate content in sediments around the Early to
Middle Eocene boundary (during NP14). This step correlates with shifts in
several proxies (e.g., color reflectance, magnetic susceptibility, NGR, TOC and
TN values) and marks a transition in time from pelagic chalk sedimentation to
clay deposition in the initial stages of sediment drift development. Middle
Eocene sediments appear cyclic, with alternating clay-rich beds and white
nannofossil ooze layers that have ~30% and 80% carbonate, respectively. TOC
values are typically 0.01%–0.57% throughout the sediment column. Organic
matter is thermally immature and relatively well preserved with low Tmax
values (380°-420°C). Organic matter throughout the sediment column is a mixture
of Type II (algal and microbial) and Type III (land plant/detrital) kerogen.
density shows a general increase downhole from 1.5 to 2.4 g/cm3.
Grain density is ~2.7 g/cm3 in Hole U1410A and both water content
and porosity show a decreasing trend downhole (from 53% to 21% for water
content and from 76% to 43% for porosity). P-wave velocity increases
progressively downhole from 1490 to 1960 m/s. Magnetic susceptibility decreases
from ~290 to –2 IU with notable steps at 30 and 45 m CSF-A but exhibits
uniform (–2 to 20 IU) values below 45 m CSF-A to the bottom of the
sediment column. Color reflectance parameters a* and b* gradually increase from
–3 to 3 down to 210 m CSF-A. Below 210 m CSF-A, a* and
b* increase to 12 and 8, respectively. L* increases downhole from 13 to
91, with steps at 115, 150, and 210 m CSF-A. NGR fluctuates from 21 to 47 cps down
to 210 m CSF-A, but then decreases from 27 to ~10 cps from 210 m CSF-A to the
bottom of the hole. Color reflectance and NGR reflect calcium carbonate
content. Thermal conductivity gradually increases downhole from 0.9 to 1.5 W/(mK).