Abstract
This paper explores the paleoseismic record potentially preserved in the upper 40 m of hydraulic piston cores collected in 1996 at two sites in
Saanich Inlet, British Columbia, during ocean drilling program (ODP) Leg 169S. The ODP cores are missing 1-2 m of water-rich sediment
directly underlying the seafloor, but this sediment is preserved in shorter piston cores collected in 1989 and 1991. The upper part of the ODP cores consists of rhythmically laminated (varved) marine mud with intercalated massive beds, interpreted to be debris flow deposits. Some of the debris flow deposits are linked to past earthquakes, including the 1946 Vancouver Island earthquake (M7.2), a great (M8-9) plate-boundary
earthquake at the Cascadia subduction zone in January 1700, and a large crustal or plate-boundary earthquake about 1000yr ago. Earthquakes
may also be responsible for debris flows in about AD 1600, 1500, 1250, 1150, 850, 450, 350, 180, and BC 200, 220, 500, 900, and 1050. If so,
the average recurrence interval for moderate to large earthquakes, which trigger debris flows in Saanich Inlet, is about 150yr. This recurrence
interval is broadly consistent with the frequency of moderate to large earthquakes in the region during the historical period. Debris flows,
however, can also be triggered by non-seismic processes, making it difficult to assemble a complete earthquake record from the Saanich Inlet
cores. We propose that extensive debris flow deposits, emplaced by single large failures or many smaller coincident failures, probably have a seismic origin.
Reprinted with permission from Elsevier Science.
Abstract
Exceptional varved sediments of 2100 years BP recovered from Saanich Inlet have been analysed using high-resolution scanning electron microscopy and spectral analysis techniques. Each varve may contain up to 22 well defined individual laminae which can be attributed to seasonal-scale processes. Sediment flux comprises alternating diatom ooze/diatomaceous mud deposited during spring through autumn and a silty-clay deposited during winter. The latter may be sporadically punctuated by clay-rich laminae. Identification of some 2000 individual consecutive laminae, based on fabric and diatom assemblage, has allowed the construction of time series data for spectral analysis. Laminae types analysed include: early spring Thalassiosira spp., late spring/early summer Skeletonema costatum, multiple summer/autumn Chaetoceros spp. diatom oozes and sporadically present clay-rich winter flood deposits. Sub-decadal periods have been identified and linked to the Quasi-Biennial Oscillation (QBO) and El Niño Southern Oscillation (ENSO), and decadal periods to the Pacific Decadal Oscillation (PDO). Comparison of spectral analysis results with modern analogues suggests associations may exist between: early spring Thalassiosira spp. laminae and stronger La Niña events; late spring/early summer S. costatum laminae and El Niño events; summer/autumn Chaetoceros spp. multiple laminae and negative Pacific Northwest Index (PNI) regimes; and sporadically present winter clay-rich laminae and PNI-regimes. The average period for an ENSO cycle was 3.6 years, QBO 2.5 years and PDO 14.8 years. Spectral analysis of the more recent PNI record shows similar significant periods of 13.2, 3.7 and 2.6 years. Multi-decadal periods recorded include: 42.2 and 31.3 years, which might suggest multiples of PDO.
Reprinted with permission from Elsevier Science.
Marine Geology Special Volume
Abstract
Continuous coring in Saanich Inlet (Ocean Drilling Program, ODP Leg 169S), British Columbia, Canada, yielded a detailed record of Late Quaternary climate, oceanography, marine productivity, and terrestrial vegetation. Two sites (1033 and 1034) were drilled to maximum depths of 105 and 118m, recovering sediments ranging in age from 13,300 to less than 300 14C yr. Earliest sediments consist of dense, largely massive, gray glaciomarine muds with dropstones and sand and silt laminae deposited during the waning stages of glaciation. Deposition of organic-rich olive gray sediments began in the fjord about 12,000 14C yr ago, under well-oxygenated conditions as reflected by the presence of bioturbation and a diverse infaunal bivalve community. At about 10,500 14C yr, a massive, gray unit, 40-50cm thick, was emplaced in a very short span of time. The unit is marked by a sharp lower contact, a gradational upper contact and an abundance of reworked Tertiary microfossils. It has been interpreted as resulting from massive flood events caused by the collapse of glacial dams in the Fraser Valley of mainland British Columbia. Progressively greater anoxia in bottom waters of Saanich Inlet began about 7000 14C yr ago. This is reflected in the preservation of varved sediments consisting of diatomaceous spring-summer laminae and terrigenous winter laminae. Correlation of the sediments was based on: marked lithologic changes, the presence of massive intervals (reflecting localized sediment gravity flow events), the Mazama Ash, occasional thin gray laminae (indicative of abnormal flood events in nearby watersheds), varve counts between marker horizons, and 71 accelerator mass spectrometry (AMS) radiocarbon dates.
Reprinted with permission from Elsevier Science.
Abstract
This paper provides: (i) a descriptive overview of the late Pleistocene and Holocene geology and geomorphology of the region surrounding Saanich Inlet; and (ii)
the palaeogeographic setting for discussion of the oceanographic record at ODP leg 169S sites 1033 and 1034. The dominant deposits and landforms in the
Saanich Inlet area are similar to those of late Pleistocene marine-influenced glacial environments and modern fjord inlets dominated by retreating tide-water
glaciers. Patterns of ice retreat, meltwater drainage and sea-level change are reconstructed for the interval 4000-15,000 calendar years before present (yrBP). The
flux of meltwater and sediment into Saanich Inlet was greatest between ca. 12,000 and 15,000yrBP. At that time, sea level was up to 90m higher relative to land
than today. During deglaciation, tidewater glaciers occupying Chemainus, Cowichan and Koksilah valleys entered a marine embayment that formed in the vicinity
of Cowichan Bay, Satellite Channel, Saanich Inlet and Saanich Peninsula. In the early Holocene, relative sea level fell to a low stand perhaps tens of metres below
the present datum, and the surface area of Saanich Inlet and Satellite Channel was much reduced. By the middle Holocene, sea level had risen to near its present
position, and modern drainage patterns and oceanographic conditions were established.
Reprinted with permission from Elsevier Science.
Abstract
Late Pleistocene deposits were cored at two sites in Saanich Inlet and provide a record of the sedimentary environment during deglaciation of this fjord. At Site 1033 at the southern end of the fjord, 59.3m of Late Pleistocene sediment was obtained in a hole drilled to 105.1mbsf. At Site 1034, 4.8km to the north, a hole was drilled to 118.2mbsf, recovering 49.8m of Late Pleistocene sediment. Sediments were deposited in this deep (>200m) fjord basin, as a lobe of the Cordilleran ice sheet retreated at the end of Fraser Glaciation. This is the first recovery of basin-fill sediments from the Pleistocene retreat of the Cordilleran ice sheet.
Lithofacies analysis, particle size measurements and 17 AMS 14C dates on marine shells or wood fragments are used to reconstruct the glacimarine sedimentary environment. Sediments are dense, gray to olive-gray terrigenous silty clay with thick, graded sand beds and interlaminated fine sand and silt with mud. Scattered dropstones, clusters of pebbles, and pods of sand and granules are common. Bioturbation, indicated by disruption of laminae and horizontal burrows or black mottles is minimal to moderate, and decreases downcore.
A calving tidewater glacier retreated northward through Saanich Inlet, however the ice-contact sediments are beneath the depth cored at both sites. The glacier retreated rapidly and the basin was open to marine exchange through Satellite Channel prior to 13,270±60 14C yr BP, the oldest date from the cores. Deposition of Lithofacies Association I occurred in an iceberg-zone depositional environment dominated by turbid meltwater plumes and intense iceberg rafting within approximately 10km of the glacier terminus. After the glacier grounded at the head of Cowichan Bay, Lithofacies Association II was deposited in the ice-distal depositional environment by turbidity currents that by-passed the sill and turbid meltwater plumes. Lithofacies Association III was deposited under post-glacial conditions at the end of the Pleistocene.
Reprinted with permission from Elsevier Science.
Abstract
Seismic stratigraphic analysis combined with results from ODP Leg 169S deep ocean drilling within Saanich Inlet to depths greater than 100m below the
seafloor provided an opportunity to study the post-glacial development of the inlet in a quantitative manner. The seismic stratigraphy of Saanich Inlet is consistent
with the general stratigraphy established for southwestern British Columbia. Sediment physical property data collected from ODP hydraulic piston cores provide
the mechanism with which to correlate the seismic stratigraphy with lithologic descriptions. Acoustic basement (seismic Unit 1) is bedrock, likely Devonian or
Carboniferous through Middle and possibly Late Cretaceous Wrangellian Terrane. Acoustic Unit 2 overlies bedrock and is interpreted as till or diamict. It is
variable in occurrence and thickness and most prominent in the central portion of the inlet, with a maximum thickness of 247m. There is no evidence of earlier
glacial advances, thus it is likely a Vashon Drift from the latest glaciation (the Fraser Stade). Acoustic Unit 3 correlates with the grey, massive, silty-clay of
lithologic Unit II, known regionally as the Capilano Formation, and locally as Victoria clay. It is a glacial-marine sediment resulting from outwash of the
deteriorating ice sheet, largely composed of silty mud with beds and stringers of sand and common ice-rafted debris, including some boulders. Sediment of this
unit infilled the basin, as evidenced by its thickness (max. 155m) and its flat-lying upper surface. Its density values show a steep, normal-consolidation profile
indicating relatively rapid deposition with no apparent over-consolidation. Hemipelagic and pelagic deposition, represented by Unit 4, became the dominant
sedimentation mechanisms in the Holocene, as glacial-marine outwash declined. This transition took place between 14,700 and 12,000yrBP, correlating with a time
of rapid glacier recession and major relative sea level lowering. Relative sea level fell to a low of at least 45m below present by about 9000yrBP. This low stand
resulted in partial isolation of the inlet and the commencement of anoxic conditions in the deeper portions of the inlet. Unit 4 demonstrates very low bulk density
and velocity values as a result of low grain densities, high porosities and in situ gas. It is a flat-lying unit throughout the inlet, pinching out on the steep inlet walls.
The unit thickens significantly to the north and then to the west. This thickening results from surface water penetration of the Cowichan River sediment plume,
terrigenous sediment input from the steep terrain on the west side of the inlet, and tidal residuals forcing sediment laden waters to the western flank of the inlet.
Incoherence of seismic reflectors within this unit may be the result of differential thickening, but may also result from occasional debris flows or other
mass-wasting processes and fault offsets.
Reprinted with permission from Elsevier Science.
Abstract
The Holocene section in Saanich Inlet, Vancouver Island, British Columbia, is 50-70m thick. Cores from Saanich Inlet obtained during Leg 169S of the Ocean
Drilling Program afford an excellent opportunity to obtain an ultrahigh-resolution paleomagnetic and environmental magnetic record for the Holocene and Late
Pleistocene of western Canada. We have used an automated, long-core cryogenic magnetometer to study over 380m of continuous u-channel samples from ODP
Sites 1033 and 1034, the two sites that constitute Leg 169S. Holocene records of paleomagnetic inclination and intensity show excellent intra-site correlation and
can be used to fine-tune the lithologic correlation among cores from each site. The Late Pleistocene magnetic records provide a means of intra-site correlation of
the otherwise featureless marine clay. Near the Holocene/Late Pleistocene boundary, both sites contain a magnetic intensity feature that is interpreted as a
Missoula-type flood event on the Fraser River. The composite Holocene inclination records from the two sites are quite similar and provide a means of
comparing current age-models that are based on radiocarbon dating of material from each site. This comparison shows only minor differences in the available
age-models. It also provides strong evidence that the sediments of Saanich Inlet represent a reliable record of geomagnetic field behavior.
Reprinted with permission from Elsevier Science.
Abstract
High-resolution grey-value time series were extracted from digital images of varved sediments in Saanich Inlet, British Columbia (ODP Sites 1033 and 1034).
Results allowed reconstruction of a ~6000yr long record with annual resolution. Composite records were compiled for Sites 1033 and 1034 by correlation of
massive beds, which represent gravity flows, and of characteristic features in the varve patterns. The varve-count age-scale was calibrated with published
radiocarbon ages. Results demonstrate that the ODP Leg 169S record is virtually complete.
Saanich Inlet varve record has the potential to provide a high-resolution climate record. Temporal variation in varve thickness is interpreted to reflect regional
precipitation history, with thick varves representing wet conditions. Long-term changes in varve thickness during the past 6000yr coincide with known changes in
global climate, but without an obvious one to one correlation between wet/dry in Saanich Inlet and warm/cold periods elsewhere. Varve thickness indicates that the
climate around Saanich Inlet was wet from the start of the varved sequence at ~6000 to ~3250yr BP, between 2100 and 1750yr BP (Roman Warm Period) and
from 500yr BP onward (including during Little Ice Age).
Reprinted with permission from Elsevier Science.
Abstract
ODP Leg 169S laminated sediment cores provided a unique opportunity to examine changes in the siliceous phytoplankton community of Saanich Inlet. These laminated sediments are rich in diatom and silicoflagellate remains as a result of the inlet's high production and excellent preservation. Our results suggest that species composition and abundance of diatoms and silicoflagellates in the inlet have changed very little since the inlet's formation. Carbon and opal data indicate an increase in primary productivity with time which is not apparent in the fossil data. However, the discrepancy between data sets may be due to changes in grazer activity which could have reduced the number of identifiable fossils. Individual species were useful for identifying changes in the inlet. Some planktonic diatoms suggest that nutrient supply was highest in the early-mid Holocene. Increases in the abundance of a partially benthic diatom, Paralia sulcata, follow variations in sea level and availability of benthic habitat in the inlet. A large peak of the silicoflagellate, Dictyocha fibula, corresponds to a catastrophic flood event in the early Holocene, which probably washed terrestrial material and low salinity water from the British Columbia mainland into Saanich Inlet. Fossil data were also analyzed to infer past changes in the environment using a weighted averaging calibration and regression technique. These data suggest that only minor variations in sea surface temperature have occurred.
Reprinted with permission from Elsevier Science.
Abstract
We assessed the potential importance of tidally-driven intrusions of autochthonous protistan plankton into Saanich Inlet, a fjord in Vancouver Island, as potential sources of fossils in the fine intra-annual sediment laminations of ODP cores. We determined the structure of protistan assemblages throughout the Inlet during July 1995 at times of successive neap and spring tides. Results were compared to a concurrent physical study of tidal flows and nutrient advection into and out of the Inlet, which allowed us to identify protistan species indicative of mixed Satellite Channel and stratified Saanich Inlet waters. These identifications were either confirmed or rejected by temporal analyses of protistan assemblages based on weekly sampling at two fixed positions, one in Saanich Inlet and one in Sidney Channel from May through October 1997. Results of both studies supported the hypothesis that the presence of a suite of diatom species, including most Chaetoceros spp., a large-celled variant of Skeletonema costatum and Thalassiosira rotula indicates the intrusion of water with elevated levels of dissolved inorganic nitrogen into Saanich Inlet from the Strait of Georgia. This indicator group of species contained additional species, but not all were observed in large numbers in 1997. Many of these species are important components of the laminated sediments of Saanich Inlet, whose presence is probably indicative of paleo-environmental conditions in the southern Strait of Georgia rather than Saanich Inlet. Effects of tidal cycles on dinoflagellate and other flagellated cells, exclusive of mastigophorans, were inconclusive and additional studies are required to elucidate details of their ecology in waters of the southern Strait of Georgia.
Reprinted with permission from Elsevier Science.
Abstract
Holocene varved sediments recovered from Saanich Inlet, ODP Leg 169S, have been analysed using high-resolution scanning electron microscope techniques. The individual centimetre-scale varves form couplets, comprising diatom ooze/diatomaceous mud deposited during spring to autumn and silty clay deposited during winter. Each individual varve may contain up to 19 laminae, recording sub-seasonal to seasonal-scale processes. These intra-annual laminae contain a range of components, including pelagic faecal pellets and aggregates of diatomaceous material. The combination of these individual components in varying proportions with a heterogeneous sediment, leads to a range of laminae fabrics. These include intact monospecific Skeletonema costatum and Thalassiosira pacifica diatom oozes and highly fragmented, aggregate- and faecal pellet-dominated diatom oozes which are typically Chaetoceros spp.-dominated. Additional laminae fabrics include diatomaceous mud, stringer-type diatomaceous mud which contains discrete diatom aggregates, homogeneous and pelleted silty clay. The varved diatom succession typically commences in early spring with Thalassiosira spp./Chaetoceros spp., followed by Chaetoceros spp. in late spring. During late spring/early summer blooms of S. costatum may be recorded, and summer to autumn production is characterised by one to several Chaetoceros spp.-dominated blooms. Inter-annual variability in diatom flux typically comprises the presence/absence of Thalassiosira spp. and S. costatum. In addition, resting spores of Chaetoceros spp., Thalassiosira nordenskioeldii and Leptocylindricus danicus are intermittently recorded. There is a major change in varve thickness from thinner varves prior to approximately 2100yr BP to thicker varves after this date, which is attributed to increased terrigenous input throughout the varve. The identification of laminae fabrics, diatom successions and a unique massive interval has enabled an inter-site correlation between sites 1033B and 1034B.
Reprinted with permission from Elsevier Science.
Abstract
Laminated biosiliceous sediments from Saanich Inlet, British Columbia (SI), the Monterey Formation, California (MF), and Santa Barbara Basin, California (SBB) are organic-rich and were studied to assess the suitability of SI and SBB as modern analogs of the Miocene MF and to explore the controls on distributions of opal and organic carbon. To this end, individual laminae and groups of laminae extracted from ODP cores and outcrop samples were analyzed using a multi-tracer geochemical approach.
Total organic carbon, opal, C:N ratios, 
13C of organic matter (OM), kerogen type and major and minor element abundances were measured. SI sediments are 52-84% detrital, 15-45% opal and 1-2% organic carbon. 13C and C:N ratios indicate a marine source of the OM present in the sediments. Samples from the upper siliceous member of the MF are 6-41% detritus, 28-87% opal, and 1-5% organic carbon. Kerogen types, C:N ratios, and 13C data are suggest mixed but predominantly marine OM. SBB samples are 59-90% detritus, 6-34% opal, 3-22% calcite, and 1-5% percent organic carbon. SI and SBB have similar bulk compositions with the exception of the presence of calcite in SBB samples. MF sediments have significantly lower detrital and higher opal contents than SI and SBB samples. These large differences suggest that SI and SBB are not appropriate modern analogs for the MF.
In SI sediments, organic carbon is concentrated in opal-rich, detritus-lean laminae and intervals. This distribution suggests that the coupling of opal and OM created in the surface ocean by diatom productivity is preserved in the sediment record. In the MF, opal and TOC are negatively correlated, implying that the coupling of opal and organic carbon did not survive the processes of settling, sedimentation, diagenesis, and/or weathering. This decoupling of organic carbon and opal in the MF is attributed to dilution of OM by high opal flux rates and/or the respiration and/or redistribution of OM during diagenesis and/or weathering.
Reprinted with permission from Elsevier Science.
Abstract
The varved marine sediments of Saanich Inlet, British Columbia, retain a detailed record of fish remains. We examine methods to process and interpret
sedimentary fish remains and explore sources of bias in transfer and preservation through time. In high-resolution box cores spanning the last 130 years, scales
outnumber vertebrae. A consistent record across replicates is recognizable once outliers are removed. Pacific herring and hake remains make up over 90% of the
identifiable remains. Cores from ODP leg 169S covered the entire Holocene; scale recovery is poor, so the record is based on fragmented bones. Bones
associated with the backbone, gill arches and fins yield the best taxonomic information. In both core sets, low-frequency signals are resolved using a five-sample
running mean. Because the data series in the short cores are autocorrelated, spectral analysis is the best approach to identify high-frequency signals that explain
much variance in the scale data. High cross-spectral coherencies confirm a basin-wide signal in scale deposition. The herring scale deposition data are compared
to recent fishery biomass estimates and confirm similarities in timing of low-frequency trends and signals. Experiments with herring in large tanks explore the
transfer of scales from fish to the ocean floor; shedding and predation are found to provide a regular rain of scales to the sediments. Overall, the sedimentary fish
remains record in basins with good preservation shows promise as a means to identify generalized long-term fish histories through the Holocene as well as a
more specific Pacific herring and hake story over the last century.
Reprinted with permission from Elsevier Science.
Abstract
Ocean Drilling Program Leg 169S retrieved a complete Holocene sequence from Saanich Inlet, British Columbia, Canada. Fish and diatom remains were
extracted from sediments at Site 1034. Very small fish bones, teeth and scales were ubiquitous except in the lowermost glaciomarine clays; scales degraded with
depth. In the identifiable fraction, Pacific herring were the most abundant with Pacific hake and cartilaginous fish yielding significant fractions. Fish remains
appear just before 12,000 BP but greatest diversity does not occur until about 6500 BP. A smoothed abundance curve highlights two periods of maximal
abundance at about 1500 and 6500 BP. Abundances in the last 1000years are lower than the rest of the record. A correlation with abundances of seven
phytoplankton taxa is significant; diatoms explain about a third of the variance. This study demonstrates the use of fish and diatoms from the same
paleosedimentary matrix to examine millennia-scale correlations between primary and tertiary production.
Reprinted with permission from Elsevier Science.
Abstract
High-resolution pollen analysis of laminated marine sediments from ODP Hole 1034B in Saanich Inlet, British Columbia reveals changes in vegetation and inferred climate during the Holocene. Four main pollen zones are discerned using constrained cluster analysis. Although the timing of major vegetation changes at the Saanich Inlet is similar to other study sites in the Pacific Northwest, the composition of pollen assemblage zones is different from the mainland sites. Vegetation assemblages reconstructed from the pollen and spore record include a Douglas-fir (Pseudotsuga menziesii) parkland with abundant grass (Poaceae) and bracken (Pteridium) between 11,450 and 8300 BP (all ages are calibrated calendar years), oak (Quercus) savanna or parkland with high grass and bracken (8300-7040 BP), a mixed deciduous/coniferous forest with oak, western hemlock (Tsuga heterophylla) and Douglas-fir (7040-5750 BP), and the development of modern coastal temperate forest with the marked expansion of cedar (Cupressaceae), western hemlock, spruce (Picea) and Douglas-fir (5750-1050 BP). Climatic periods inferred from the cores include an early Holocene warm/dry interval (11,450-8300 BP), a warm period with mild winters (8300-7040 BP), a period of transitional mid-Holocene climate (7040-5750 BP), and the advent of a relatively cool/wet neoglacial climate after 5750 BP. Modern conifer forests and oak savannas became established by about 3800 BP. The Saanich Inlet pollen record indicates that vegetation and inferred climate change was particularly rapid between 8700 and 8300 BP when grass and bracken abruptly decrease and oak becomes a significant component of the paleovegetation. Because neoglacial conditions have prevailed from 3800 years to present in the Pacific Northwest, factors other than climate, such as anthropogenic modification of the landscape, may be responsible for the persistence of oak savannas.
Reprinted with permission from Elsevier Science.
Abstract
Little is known of long-term processes affecting microbial abundance in buried marine sediments. In collaboration with geochemists and sedimentologists involved in ODP Leg169S, we undertook a study of bacterial and viral abundance throughout the entire Holocene sediment section in Saanich Inlet, British Columbia, Canada. Sediments were sampled at 1.5-m intervals from the sediment surface down into Pleistocene sequences at depths of >100m. Preparations of formalin-fixed sediment were stained with the nucleic acid stain Yo-Pro and bacteria and viruses were enumerated using epifluorescence microscopy. Viral presence was confirmed by electron microscopy. More widely spaced measurements of adenosine triphosphate (ATP) and the biogenic pore water gases H2, CH4 and CO were used as indices of microbial metabolic activity. Bacterial and viral abundances were high (>109 gdw-1) in these organic-rich sediments relative to oceanic areas, and were highly correlated, indicating a probable close functional dependence characteristic of predator-prey relations. The upper Holocene section showed a significant subsurface peak in microbial abundance that was correlated negatively with sediment organic matter content, but corresponded with biogenic gas accumulation. The interpretation of these and other significant trends is discussed in relation to the Holocene/late Pleistocene history of organic matter sedimentation and diagenetic processes.
Reprinted with permission from Elsevier Science.
Abstract
Molecular biology offers many new tools for the characterisation of mixed communities of microorganisms. Approaches that require the extraction and
purification of bulk community DNA from sediments and soils must contend with contaminants such as humic acids and heavy metals that can interfere with
subsequent genetic analysis. This paper reports on the adaptation of DNA extraction and purification techniques to samples of organic rich sediments collected
during the Ocean Drilling Program Leg 169S in Saanich Inlet, British Columbia. In an extraction time series, DNA yield increased up to 48h (at 37°C), after
which there were negligible increases in yield and signs of degradation. Resulting extracts, rich in humic substances, blocked the DNA polymerase enzyme even
at high dilution. Standard purification procedures (phenol/chloroform extraction followed by silica-based DNA binding or agarose gel electrophoresis) proved
ineffective in removing PCR inhibitors. The inhibitory effect was eliminated by cesium chloride density gradient centrifugation with eukaryote DNA added as a
carrier, permitting amplification and cloning of SSU (small subunit) rRNA genes. A detailed extraction and purification protocol is presented. These procedures,
although time-consuming, may be applicable to other sediment types where microbial DNA is particularly difficult to extract or purify.
Reprinted with permission from Elsevier Science.
Abstract
Sites 1033 and 1034 of ODP Leg 169S in Saanich Inlet have an unusual diagenetic system, that has the appearance of being depth reversed, i.e. a bacterial methane accumulation zone underlain by a sulphate reduction zone. During the late Pleistocene grey, undifferentiated, glacio-marine clays were deposited with low Corg contents (<0.4wt.%), and interstitial fluids replete in SO4 (ca. 27mM), devoid of CH4 and low in nutrients. This indicates oxic conditions are present, reflecting the open exchange of waters with Haro Strait during the Pleistocene before the Saanich Peninsula emerged. In the earliest Holocene (ca. 11,000years BP) the inlet was formed, severely restricting water circulation, and leading to the presence of anoxic bottom waters. The sediments are laminated and show a dramatic rise to high Corg, Norg and Stot contents (up to 2.5, 0.4, 1.4wt.%, respectively) over a period of ca. 1000years. The nutrient concentrations are especially high (TA, NH4, PO4 up to 115meq/l, 20mM and 400µM, respectively), SO4 is exhausted and CH4 is prolific. Stable carbon isotope ratio measurements of CH4 and co-existing CO2 indicate that methanogenesis is via carbonate reduction (13C-CH4 ca. -60 to -70
, 13C-CO2 ca. +10). At the sulphate-methane interfaces, both at the near-surface and at 50mbsf (Site 1033) and 80mbsf (Site 1034) methane consumption by sulphate reducing bacteria is intensive.
Reprinted with permission from Elsevier Science.
Abstract
Changes in palaeoproduction in Saanich Inlet, British Columbia, were examined from sediments using total organic carbon contents and stable carbon isotope ratios. Sediments were obtained from Holes 1033B and 1034B of Ocean Drilling Program Leg 169S. These cores contain two distinct zones: (1) carbon poor (%Corg<0.5wt.%) glaciomarine muds from the upper Pleistocene, and (2) carbon rich (%Corg1-3wt.%), well-laminated sediments from the Holocene. A slight monotonic rise in %Corg and 13Corg throughout the Holocene suggests that primary production in the inlet has been steadily increasing. Some influence of changes in local land vegetation is also evident. Sharp decreases in %Corg and 13Corg in the early Holocene probably represent material deposited from a major flood. Differences in organic 13Corg between light and dark laminae are related to seasonal variations in species composition temperature and nutrient conditions.
Reprinted with permission from Elsevier Science.
Abstract
Coring at site ODP 1033B in Saanich Inlet recovered 59.4m of mainly laminated olive-grey diatom ooze and an underlying 55.15m of massive grey to olive-grey silty clay. Based on AMS radiocarbon dating, the boundary between the two units is between 11,000 and 13,800 calibrated years BP, and represents the Holocene-Pleistocene boundary. The lower unit represents glaciomarine deposition, whereas deposition of the upper unit began when the modern semi-restricted physiography of the fjord was established following glacial rebound and highly productive marine conditions were established. The glaciomarine clay is almost entirely terrigenous, whereas the diatom ooze contains 2-3wt.% organic C and 20-40wt.% biogenous silica; CaCO3 contributions are minor, but there are several peaks in carbonate abundance in the upper unit. The isotopic composition of organic C and total N suggests that organic matter in the glaciomarine clay is dominantly terrestrial (13Corganic<-25 and 15Ntotal=ca. 3) and in the diatom oozes it is mainly marine (13Corganic>-22 and 15Ntotal=ca. 10). The heavy 15Ntotal values probably record a contribution of isotopically heavy nitrate to the surface waters of the inlet that is transported to British Columbia (BC) coastal waters from the eastern tropical Pacific by the California Undercurrent. Major and minor elemental data suggest that the composition of the terrigenous material and its grain-size has changed over the last 15kyr, and there are marked enrichments in several redox-sensitive elements in the diatom oozes. Thus, Cu, Mn, Mo, Ni, Pb, V and Zn have higher concentrations in the upper unit; Br and I are also enriched because of their association with organic matter. Mn is enriched in the anoxic diatom oozes due to the presence of manganoan carbonate (Mn peaks generally corresponding with carbonate peaks) formed in the sediment when deep water renewal caused precipitation of Mn oxyhydroxides, which dissolved in the anoxic sediment and was precipitated as a diagenetic phase. The remaining metals are enriched because of their removal to the sediment as sulphides (Cu, Mo, Ni, Pb and Zn) or as particle-reactive reduced species (V). Cr enrichment is obscured by the presence of Fe-rich chlorite. The lag in the enrichment of Mo with respect to organic C in the sediments indicates that anoxia developed some time after marine production increased following the semi-isolation of the fjord.
Reprinted with permission from Elsevier Science.
Abstract
Uncertainty currently exists about the removal of carbon (C) and phosphorus (P) from the oceanic reservoir, especially in low oxygen settings. In this paper, the cycling of C and P is examined in sediments from the anoxic Saanich Inlet, cored by Ocean Drilling Program (ODP) Leg 169S in 1996 at two sites. Although Corg/Porg ratios are high and increase with depth in the Saanich Inlet, this effect is due largely to a remobilization of P from an organic matter sink to an authigenic sink. Reducible sedimentary components act as temporary shuttles in this process even in this anoxic setting, with the ultimate burial sink for the remobilized P being carbonate fluorapatite. The effective Corg/Preactive molar ratio appears to be about 150-200, indicating some preferential loss of P compared to C during organic matter degradation, but not approaching previously reported values of over 3000 in black shales. Reactive P accumulation rates in this basin range from 10,000-60,000µmol/cm2/kyr, greatly exceeding the range of 500-8000µmol/cm2/kyr found in most continental-margin settings, including regions of modern phosphogenesis. The initiation of marine sedimentation in the Saanich Inlet occurred after deglaciation, and the high rates of P burial seen here may provide an end-member example of the effects of sea level and margin sedimentation on the distribution of P within the marine P cycle.
Reprinted with permission from Elsevier Science.
Abstract
The entire suite of halogens was measured in the pore fluids of Hole 1033B and 1034B from Saanich Inlet: ODP Leg 169S. The fast sedimentation rates and large amount of organic carbon burial coupled with anoxia of the overlying waters promotes an advanced stage of diagenesis within the sediment column. Chloride interstitial water profiles suggest salinity variations within the waters of Saanich Inlet. Concentration profiles for iodide and bromide support the argument that they are produced through the degradation of organic matter. Although the concentration increases in I- and Br- indicate that these halides are not regenerated in similar proportions to marine organic matter, it appears that iodide and bromide are regenerated to similar degrees within the sediment column and in similar proportions to the sediment halide concentrations. Fluoride porewater values show a complicated pattern, most likely caused by secondary reactions involving complexation with Mg2+, carbonate fluorapatite precipitation, carbonate mineral diagenesis, and/or uptake into alumino-silicate minerals.
Reprinted with permission from Elsevier Science.
Abstract
Holocene laminated sediments in Saanich Inlet, British Columbia, are interrupted by frequent, non-laminated, massive layers. These layers may be debris flows
released by earthquakes or bioturbated sediments deposited during periods of relatively high bottom water oxygen concentration and/or low surface productivity,
or both. We determined the organic carbon content and the concentration of a suite of redox-sensitive metals in bulk sediments at approximately 1-cm resolution
across a laminated-massive-laminated interval (ODP leg 169S Site 1033, Hole B, 4H4 54-74cm), to determine the redox conditions under which the massive layer
was deposited. Our results indicate that this massive interval was deposited under anoxic bottom waters. Manganese/Al ratios are consistently low throughout the
massive section, while Mo/Al, Cd/Al, Re/Al, and U/Al ratios are enriched relative to their metal/Al ratios in detrital material (represented by Cowichan River
suspended sediments). The concentration of organic carbon in the lower portion of the massive layer is higher than in the upper portion, which has a
concentration similar to that in the overlying and underlying laminated sediments. Well-defined peaks in Mo/Al, Cd/Al, and Re/Al and a broad peak in U/Al occur
in the lower portion of the massive layer. The positions of the Cd/Al, Re/Al, and Mo/Al peaks, as well as the increase in organic carbon content with depth in the
massive layer, are best explained by a process of diagenetic redistribution of metals that occurred after the massive layer was emplaced.
Reprinted with permission from Elsevier Science.
Abstract
We measured the concentrations of redox-sensitive trace metals (Mn, V, Mo, U, Cd and Re) in sediments from ODP Leg 169S Hole 1033B in Saanich Inlet,
British Columbia, to determine changes in redox conditions associated with the onset of laminated sediments at ~12.5kyr. The most striking result is a large peak
in authigenic Re along with detrital levels of Mo at the glacial terrigenous clay-diatomaceous sediment transition. In contrast, the underlying glacial terrigenous
clay, which extends throughout the bottom section of the core, is chemically similar to detrital concentrations, either Cowichan River particulates or average shale
values. These data suggest a period of oxic bottom waters but reducing pore-waters. This could be due to the dramatic transformation of Saanich Inlet during the
late deglaciation from an open bay to an inlet, which restricted circulation and slowed bottom water oxygen renewal. A peak and gradual increase in authigenic
Mn in younger sediments subsequent to the Re peak suggests that increasingly oxic conditions followed the authigenic enrichment in Re. These conditions could
be connected to the Younger Dryas cooling period, which was coincident with an increase in well-oxygenated upwelled waters on the west coast of North America
that form the bottom waters of Saanich Inlet.
Metal concentrations in a gray clay bed (~11kyr) are similar to their concentrations in the glacial terrigenous clay, implying that they have a common source.
Authigenic enrichments of Re with little authigenic Mo and Cd suggest that before the deposition of this bed, bottom waters were oxic and pore-water oxygen
was consumed in the top centimeter or less. Laminations above the clay layer suggest anoxic conditions, which are also indicated by higher authigenic Mo and Cd
and slightly lower Re/Mo ratios in these sediments. The basin remained mostly anoxic after the gray clay was emplaced, as seen by continuous authigenic
enrichment of the redox-sensitive trace metals. These results are consistent with increased stratification of the water column, brought about by an influx of fresh
water to the basin by a large flood.
Reprinted with permission from Elsevier Science.
Abstract
Saanich Inlet has been a highly productive fjord since the last glaciation. During ODP Leg 169S, nearly 70m of Holocene sediments were recovered from Hole 1034 at the center of the inlet. The younger sediments are laminated, anaerobic, and rich in organic material (1-2.5wt.% Corg), whereas the older sediments below 70mbsf are non-laminated, aerobic, with glacio-marine characteristics and have a significantly lower organic matter content. This difference is also reflected in the changes of interstitial fluids, and in biomarker compositions and their carbon isotope signals. The bacterially-derived hopanoid 17
(H),21
(H)-hop-22(29)-ene (diploptene) occurs in Saanich Inlet sediments throughout the Holocene but is not present in Pleistocene glacio-marine sediments. Its concentration increases after ~6000 years BP up to present time to about 70µg/g Corg, whereas terrigenous biomarkers such as the n-alkane C31 are low throughout the Holocene (<51µg/g Corg) and even slightly decrease to 36µg/g Corg at the most recent time. The increasing concentrations of diploptene in sediments younger than ~6000 years BP separate a recent period of higher primary productivity, stronger anoxic bottom waters, and higher bacterial activity from an older period with lesser activity, heretofore undifferentiated. Carbon isotopic compositions of diploptene in the Holocene are between -31.5 and -39.6 PDB after ~6000 years BP. These differences in the carbon isotopic record of diploptene probably reflect changes in microbial community structure of bacteria living at the oxic-anoxic interface of the overlying water column. The heavier isotope values are consistent with the activity of nitrifying bacteria and the lighter isotope values with that of aerobic methanotrophic bacteria. Therefore, intermediate 13C values probably represent mixtures between the populations. In contrast, carbon isotopic compositions of n-C31 are roughly constant at -31.4±1.1 PDB throughout the Holocene, indicating a uniform input from cuticular waxes of higher plants. Prior to ~6000 years BP, diploptene enriched in 13C of up to -26.3 PDB is indicative of cyanobacteria living in the photic zone and suggests a period of lower primary productivity, more oxygenated bottom waters, and hence lower bacterial activity during the earliest Holocene.
Reprinted with permission from Elsevier Science.