Seasonal variability in turbidity currents in Lake Ohau, New Zealand, and their influence on sedimentation

Layers of sediment that are deposited on the floor of Lake Ohau, New Zealand, offer a means to reconstruct past climate conditions in the Southern Hemisphere at subdecadal and annual resolution. A robust understanding of the modern physical processes that control the influx and dispersal of sediment in the lake is required to reconstruct climate from these sedimentary archives. In this study, water temperature and velocity measurements collected during 2012–13 were analysed to determine the primary physical processes that influence sediment transport in the lake. Sediment input from river inflow occurs throughout the year but exhibits strong seasonal variation. Large inflow events (Q>500m3s–1) that follow strong summer rainstorms trigger high-concentration turbidity currents, which are the main agents for sediment delivery and deposition. During winter, smaller turbidity currents also occur after rain events and contribute to annual sediment accumulation. In addition, large internal waves were observed during the summer and may influence sedimentation. In conclusion, several processes including river inflow, internal waves and convectively driven flows control sediment deposition and accumulation in the Lake Ohau system. We utilise these observations to establish a conceptual model to explain the observed infill stratigraphy in Lake Ohau and guide interpretation of the longer sedimentary record.

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Building an 18 000-year-long paleo-earthquake record from detailed deep-sea turbidite characterisation in Poverty Bay, New Zealand

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-2077-2012 ◽

2012 ◽

Vol 12 (6) ◽

pp. 2077-2101 ◽

Cited By ~ 30

Author(s):

H. Pouderoux ◽

G. Lamarche ◽

J.-N. Proust

Keyword(s):

New Zealand ◽

Continental Slope ◽

Water Depth ◽

Source Area ◽

Large Mass ◽

P Wave ◽

Turbidity Currents ◽

Slope Failures ◽

High Concentration ◽

Triggering Mechanism

Abstract. Two ~20 m-long sedimentary cores collected in two neighbouring mid-slope basins of the Paritu Turbidite System in Poverty Bay, east of New Zealand, show a high concentration of turbidites (5 to 6 turbidites per meter), interlaid with hemipelagites, tephras and a few debrites. Turbidites occur as both stacked and single, and exhibit a range of facies from muddy to sandy turbidites. The age of each turbidite is estimated using the statistical approach developed in the OxCal software from an exceptionally dense set of tephrochronology and radiocarbon ages (~1 age per meter). The age, together with the facies and the petrophysical properties of the sediment (density, magnetic susceptibility and P-wave velocity), allows the correlation of turbidites across the continental slope (1400–2300 m water depth). We identify 73 synchronous turbidites, named basin events, across the two cores between 819 ± 191 and 17 729 ± 701 yr BP. Compositional, foraminiferal and geochemical signatures of the turbidites are used to characterise the source area of the sediment, the origin of the turbidity currents, and their triggering mechanism. Sixty-seven basin events are interpreted as originated from slope failures on the upper continental slope in water depth ranging from 150 to 1200 m. Their earthquake trigger is inferred from the heavily gullied morphology of the source area and the water depth at which slope failures originated. We derive an earthquake mean return time of ~230 yr, with a 90% probability range from 10 to 570 yr. The earthquake chronology indicates cycles of progressive decrease of earthquake return times from ~400 yr to ~150 yr at 0–7 kyr, 8.2–13.5 kyr, 14.7–18 kyr. The two 1.2 kyr-long intervals in between (7–8.2 kyr and 13.5–14.7 kyr) correspond to basin-wide reorganisations with anomalous turbidite deposition (finer deposits and/or non deposition) reflecting the emplacement of two large mass transport deposits much more voluminous than the "classical" earthquake-triggered turbidites. Our results show that the progressive characterisation of a turbidite record from a single sedimentary system can provide a continuous paleo-earthquake history in regions of short historical record and incomplete onland paleo-earthquake evidences. The systematic description of each turbidite enables us to infer the triggering mechanism.

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Evidence for seiches and short‐period internal waves in lake Tekapo, South Island, New Zealand

New Zealand Journal of Marine and Freshwater Research ◽

10.1080/00288330.1974.9515524 ◽

1974 ◽

Vol 8 (3) ◽

pp. 541-550 ◽

Cited By ~ 1

Author(s):

N. M. Ridgway

Keyword(s):

New Zealand ◽

Internal Waves ◽

Short Period

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Environment of Deposition and Paleogeography of the Late Cretaceous Glenburn Formation, Eastern North Island, New Zealand

10.26686/wgtn.17071979 ◽

2021 ◽

Author(s):

◽

James McClintock

Keyword(s):

New Zealand ◽

Late Cretaceous ◽

Large Scale ◽

East Coast ◽

Three Dimensional ◽

Depositional Environments ◽

Tectonic Deformation ◽

Turbidity Currents ◽

Submarine Fan ◽

Submarine Channels

The Glenburn Formation of the East Coast of New Zealand is a Late Cretaceous sedimentary formation consisting of alternating layers of sandstone, mudstone and conglomerate. The Glenburn Formation spans a depositional timeframe of over 10 Ma, is over 1000 m thick, is regionally extensive and is possibly present over large areas offshore. For these reasons, it is important to constrain the paleoenvironment of this unit. Late Cretaceous paleogeographic reconstructions of the East Coast Basin are, however, hampered by a number of factors, including the pervasive Neogene to modern tectonic deformation of the region, the poorly understood nature of the plate tectonic regime during the Cretaceous, and a lack of detailed sedimentological studies of most of the region’s Cretaceous units. Through detailed mapping of the Glenburn Formation, this study aims to improve inferences of regional Cretaceous depositional environments and paleogeography. Detailed facies based analysis was undertaken on several measured sections in eastern Wairarapa and southern Hawke’s Bay. Information such as bed thickness, grain size and sedimentary structures were recorded in order to identify distinct facies. Although outcrop is locally extensive, separate outcrop localities generally lie in different thrust blocks, which complicates comparisons of individual field areas and prevents construction of the large-scale, three-dimensional geometry of the Glenburn Formation. Glenburn Formation consists of facies deposited by sediment gravity flows that were primarily turbidity currents and debris flows. Facies observed are consistent with deposition on a prograding submarine fan system. There is significant variation in facies both within and between sections. Several distinct submarine fan architectural components are recognised, such as fan fringes, fan lobes, submarine channels and overbank deposits. Provenance and paleocurrent indicators are consistent with deposition having occurred on several separate submarine fans, and an integrated regional paleogeographic reconstruction suggests that deposition most likely occurred in a fossil trench following the mid-Cretaceous cessation of subduction along the Pacific-facing margin of Gondwana.

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Reconstruction of fire regime changes in the French Mediterranean region during the last 8,500 years using microcharcoal

10.5194/egusphere-egu21-6008 ◽

2021 ◽

Author(s):

Marion Genet ◽

Anne-Laure Daniau ◽

Maria-Angela Bassetti ◽

Bassem Jallali ◽

Marie-Alexandrine Sicre ◽

...

Keyword(s):

Biomass Burning ◽

Mediterranean Region ◽

Fire History ◽

Fine Particles ◽

Fire Regime ◽

Hot Spot ◽

Sediment Delivery ◽

Climate Conditions ◽

North West ◽

Gulf Of Lion

Nowadays, the Mediterranean region is strongly impacted by fires. Projected warming scenarios suggest increasing fire risk in this region considered as hot-spot of the climate change (Liu et al., 2010; Pechony and Shindell, 2010). However, models based on modern-day statistical relationships do not properly account for interactions between climate, vegetation, and fire. In addition, process-based models must be tested not only against modern observations but also under different past climate conditions reflecting the range of climate variability projected for the next centuries (Hantson et al. 2016). Marine sediments are a major source of fire history of nearby land masses. Here, we present a unique 8,500 yr long record of biomass burning changes from southeastern France based on a marine microcharcoal sedimentary record from the Gulf of Lion, located in the subaqueous Rhone river delta. Sediment delivery to the Gulf of Lion comes mainly from the Rh&#244;ne River draining a large watershed in southeast France (ca.100,000 km2). Due to the direction of dominant winds blowing from the North-North-West (Mistral and Tramontane) and carrying fine particles from the land to the sea, the microcharcoal record likely reflects the biomass burning in the Rhone watershed and South-East of France. Our results show multi-centennial to millennial changes in biomass burning with a periodicity &#160;of 1000 years for the full record and between 500 and 700 years before 5,000 cal BP and after 3,000 cal BP. Large peaks of biomass burning are associated with marked dry periods observed in the region. Burning of biomass is higher when the region is dominated by xerophytic vegetation than when mesophyte vegetation dominates. The trend and periodicity of the biomass burning record suggest a predominant climatic control of fire occurrences since 8,500 cal BP in this region.

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Neanderthal landscapes and subsistence strategies during late Quaternary glacial-interglacial periods: insights from the avian assemblages of Grotta del Cavallo (Apulia, Southern Italy)

10.5194/egusphere-egu21-10115 ◽

2021 ◽

Author(s):

Lisa Carrera ◽

Daniele Scarponi ◽

Fabio Martini ◽

Lucia Sarti ◽

Marco Pavia

Keyword(s):

Southern Italy ◽

Late Quaternary ◽

Sediment Accumulation ◽

Sampling Effort ◽

Paleolithic Site ◽

Climate Conditions ◽

Bird Assemblages ◽

Depositional Processes ◽

Feeding Activities ◽

The Rich

Grotta del Cavallo, a well-known Paleolithic site in Southern Italy (Nard&#242;, Apulia), preserves one of the most important Italian Middle Paleolithic sequences. Its stratigraphic succession records the presence of Neanderthals from Marine Isotope Stage (MIS) 7 to 3, providing substantial insights on their lifeways. Here we present the taxonomic and taphonomic analysis of the bird assemblages associated to Neanderthal occupation. The rich avifaunal assemblages allowed paleoenvironmental and paleoclimatic reconstructions, noticeably improving the reconstruction of the landscape that was exploited by Neanderthals throughout the last glacial-interglacial cycles. Based on the bird taxa identified in the assemblages, Grotta del Cavallo was mainly surrounded by extensive grasslands and shrublands, with scattered open woodland and rocky outcrops, during MIS 7, 6 and 3. The coastal plain, that is currently underwater due to Holocene relative sea-level rise, hosted wetlands in the cooler periods, when it was exposed. In the cool-temperate climatic phase attributed to MIS 3, bird taxa of water and wet environments proportionally increased, as well as coverage-based rarefied richness values. This is possibly due to the expansion of wetland areas, linked to more humid conditions, or to the shorter distance of the wetland settings from the cave, compared to MIS 6 (glacial period). A consequent higher heterogeneity of the landscape is retained to drive the increased richness. The sampling effort allowed to retrieve bird taxa that provided significant paleoclimatic insights, such as Branta leucopsis, an arctic breeder, and other species currently spread at higher altitudes, that reinforce previously obtained geochemical derived inference of climate conditions cooler than the present ones. The bird assemblages also provided the first occurrence ever of Larus genei, the first Italian occurrence of Emberiza calandra, the oldest Italian occurrence of Podiceps nigricollis, and the occurrence of Sylvia communis (a species rarely retrieved in the fossil record). Ordination analyses of the bird dataset detected the drivers of taphonomic degradation and the agents responsible for the accumulation of the avian bones: modifications are mainly due to physical sin- and post-depositional processes, whereas accumulation is mainly attributed to short-range physical processes of sediment accumulation, feeding activities of nocturnal raptors and, to a lesser extent, human activities. In detail, traces found on a few bones suggest that Neanderthals introduced some of the birds in the cave with alimentary purposes, providing the earliest Italian evidence of bird exploitation ever.

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Spatial and temporal patterns of off-slope sediment delivery for small catchments subject to shallow landslides within the Waipaoa catchment, New Zealand

Geomorphology ◽

10.1016/j.geomorph.2011.12.037 ◽

2012 ◽

Vol 141-142 ◽

pp. 150-159 ◽

Cited By ~ 16

Author(s):

Katie E. Jones ◽

Nicholas J. Preston

Keyword(s):

New Zealand ◽

Temporal Patterns ◽

Shallow Landslides ◽

Spatial And Temporal Patterns ◽

Sediment Delivery ◽

Slope Sediment ◽

Small Catchments

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Estimation of temporally averaged sediment delivery ratio using aggradational terraces in headwater catchments of the Waipaoa River, North Island, New Zealand

Earth Surface Processes and Landforms ◽

10.1002/1096-9837(200101)26:1<1::aid-esp146>3.0.co;2-9 ◽

2001 ◽

Vol 26 (1) ◽

pp. 1-16 ◽

Cited By ~ 36

Author(s):

Mio Kasai ◽

Tomomi Marutani ◽

Leslie M. Reid ◽

Noel A. Trustrum

Keyword(s):

New Zealand ◽

Delivery Ratio ◽

Sediment Delivery Ratio ◽

Sediment Delivery ◽

Headwater Catchments

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A foraminiferal proxy record of 20th century sea-level rise in the Manukau Harbour, New Zealand

Marine and Freshwater Research ◽

10.1071/mf11208 ◽

2012 ◽

Vol 63 (4) ◽

pp. 370 ◽

Cited By ~ 10

Author(s):

Hugh R. Grenfell ◽

Bruce W. Hayward ◽

Ritsuo Nomura ◽

Ashwaq T. Sabaa

Keyword(s):

New Zealand ◽

Salt Marsh ◽

Sea Level Rise ◽

Sea Level ◽

20Th Century ◽

Tide Gauge ◽

Sediment Accumulation ◽

Proxy Record ◽

Tide Gauge Record ◽

Tidal Salt Marsh

The present study aimed to extract a sea-level history from northern New Zealand salt-marsh sediments using a foraminiferal proxy, and to extend beyond the longest nearby tide-gauge record. Transects through high-tidal salt marsh at Puhinui, Manukau Harbour, Auckland, New Zealand, indicate a zonation of dominant foraminifera in the following order (with increasing elevation): Ammonia spp.–Elphidium excavatum, Ammotium fragile, Miliammina fusca, Haplophragmoides wilberti–Trochammina inflata, Trochamminita salsa–Miliammina obliqua. The transect sample faunas are used as a training set to generate a transfer function for estimating past tidal elevations in two short cores nearby. Heavy metal, 210Pb and 137Cs isotope analyses provide age models that indicate 35 cm of sediment accumulation since ~1890 AD. The first proxy-based 20th century rates of sea-level rise from New Zealand’s North Island at 0.28 ± 0.05 cm year–1 and 0.33 ± 0.07 cm year–1 are estimated. These are faster than the nearby Auckland tide gauge for the same interval (0.17 ± 0.1 cm year–1), but comparable to a similar proxy record from southern New Zealand (0.28 ± 0.05 cm year–1) and to satellite-based observations of global sea-level rise since 1993 (0.31 ± 0.07 cm year–1).

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Sediment Budgets and Sediment Delivery Ratios in River Systems

Environmental Science ◽

10.1093/obo/9780199363445-0058 ◽

2016 ◽

Author(s):

Gary Brierly ◽

Jon Tunnicliffe

Keyword(s):

Landscape Connectivity ◽

Sediment Accumulation ◽

River Management ◽

Sediment Flux ◽

River Systems ◽

Catchment Scale ◽

Sediment Delivery ◽

Sediment Movement ◽

Sediment Budgets ◽

Continental Scale

The term sediment flux refers to sediment movement through landscapes. Analogous to “flux” in physics, i.e., the rate of flow of a property per unit area, sediment flux is the amount of sediment that flows through a cross-section of river per unit time. The magnitude of sediment flux is moderated by catchment processes such as sediment production (erosion), sediment accumulation (deposition) and intervening processes of sediment storage and reworking (transfer). Patterns and rates of sediment flux vary over a wide range of spatial and temporal scales, from grain to grain and landform scale analyses over near instantaneous timeframes through reach and catchment-scale analyses that are typically performed over decadal to millennial timescales to continental-scale appraisals over millions of years. Sediment movement is a key physical driver of natural environments. It exerts a critical influence upon the morphology, process regime, and evolutionary traits of landscapes. For example, as sediment budgets quantify sediment transport pathways, they can be used to analyze the critical factors that affect landscape development. Sediment flux exerts a critical influence upon the physical template (habitat distribution) of river systems. As such, it is a key consideration in river management and restoration. Analysis of source-to-sink relationships at the catchment scale (and associated sediment budgets) highlights controls upon sediment delivery and the influence of landscape connectivity. Emphasis here is placed upon valley floor processes, giving only partial attention to hillslope forms and processes or consideration of lakes, deltas, and nearshore marine environments. Textbooks and journals that present overviews of sediment flux in river systems are considered first. A brief overview of global scale sediment flux summarizes the movement of sediment from terrestrial areas to the ocean and the imprint of human activities. Most of this contribution focuses on catchment-scale sediment budgets, emphasizing variability in sediment sources (hillslope inputs and reworking on valley floors), the thorny question of scale relations, controls upon the sediment delivery ratio, and the influence of landscape connectivity. In many instances, disturbance events disrupt the sediment regime of a river, creating distinct pulses (or waves) that are transferred downstream by dispersion or migration processes. This is followed by an analysis of approaches to measurement of sediment flux, differentiated in relation to conventional field techniques, use of sediment fingerprinting, and the emergence of a range of remotely sensed technologies. The final sections of this article outline implications of human-induced alterations to sediment flux for river management. Appraisal of sediment disasters (impacts of dams, fine-grained sediment accumulation, and mining activities) is followed by an assessment of implications for river restoration.

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