A Poor Relationship Between Sea Level and Deep-Water Sand Delivery

Harris, Ashley D.; Baumgardner, Sarah; Sun, Tao; Granjeon, Didier

doi:10.1016/j.sedgeo.2018.04.002

Cited by 25 publications

(33 citation statements)

References 48 publications

(76 reference statements)

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“…Even though this is true for a single eustatic cycle (~10 1 -10 2 k.y. ), our results suggest that the influence of the frequency of sea-level change is minor on the long-term deep-water sediment proportion, because the cumulative time for the shoreline to stay below the shelf edge at the million-year time scale is similar despite varying frequencies of sealevel change (see also Harris et al, 2018).…”

Section: Sediment Volume Partitioning Under Different Eustatic and Shmentioning

confidence: 58%

Accommodation- versus supply-dominated systems for sediment partitioning to deep water

Zhang

Kim

Olariu

et al. 2019

Geology

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Several decades of studies on shelf-margin evolution have led to recognition that both accommodation-dominated and supply-dominated sediment-delivery systems are capable of transporting sediments from the shelf down into deep-water basins. The former case relies on falling sea level and lowstands to move deltas to the shelf edge, whereas the latter depends on well-supplied deltas reaching the shelf edge regardless of sea-level rise. However, it remains unclear how to distinguish between the two sediment-dispersal alternatives, and which of these is more efficient in delivering sediments to deep water. We explore sediment-volume partitioning into deep-water areas by analyzing >1600 runs of a geometric delta model with varying eustatic, shelf-morphologic, and sediment-supply conditions. Previous studies suggest that greenhouse eustatic (low amplitude and frequency) conditions generate lower shelf accommodation, and permit the shoreline to arrive at the shelf edge quickly. Further investigation reveals that (1) this argument works only for the supply-dominated system, and (2) the proportion of total sediment that reaches deep water is not correlated to the frequency of sea-level change, but depends strongly on the shelf width and the amplitude of sea-level change. We suggest a ratio between (1) the product of shelf width and the amplitude of sea-level change and (2) total sediment supply to quantitatively characterize the sediment dispersal system. A ratio of 0.4 forms a good boundary between accommodation-and supply-dominated systems in the modeling results, and in three well-studied ancient systems (the Maastrichtian Washakie Basin, Wyoming, USA; the Pliocene paleo-Orinoco margin, Trinidad and Tobago; and the Miocene New Jersey margin, northeastern USA). This work also suggests that the sediment mass balance becomes more important for continental margin building regardless of sea-level scenarios over the longer term.

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Section: Sediment Volume Partitioning Under Different Eustatic and Shmentioning

confidence: 58%

Accommodation- versus supply-dominated systems for sediment partitioning to deep water

Zhang

Kim

Olariu

et al. 2019

Geology

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“…I start with a general summary of my experimental findings and a comparison to the observations from the numerical experiments of Harris et al (2016Harris et al ( , 2018. For this comparison I loosely upscale the experimental stages to field conditions using the emergent experimental autogenic scales.…”

Section: Discussionmentioning

confidence: 99%

“…Motivating this experimental study are a suite of results from numerical experiments that explore the impact of RSL variations on sediment dispersal across the shelf-edge during icehouse vs. greenhouse Earth conditions (Harris et al, 2016(Harris et al, , 2018). The numerical model used in these studies, Dionisos, simulates sediment transport at basinal length-scales and geological timescales based off diffusive transport of sediment (Granjeon, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…While peak delivery of sand to the deep marine did occur during short periods of sea level fall in the variable eustacy model, similar episodes of sand delivery occur in the constant eustacy model when transport systems occasionally reached and became temporarily locked at the shelf-edge. 2The delivery of sand to the deep marine is not well correlated to rate or amplitude of sea level fall, which holds regardless of the diffusion coefficients used in the models (Harris et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Morphodynamics and Stratigraphic Architecture of Shelf-Edge Deltas Subject to Constant vs. Dynamic Environmental Forcings: A Laboratory Study

Straub

2019

Front. Earth Sci.

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When deltas dock at continental margins they construct thick stratigraphic intervals and activate continental slope sediment routing systems (SRS). Given their thickness, these deposits have the capacity to store detailed paleo-environmental records. Several competing theories describe how SRS comprised of linked deltas-continental slopes respond to sea level cycles of varying magnitude and periodicity. I explore this in a physical experiment where the topography of a coupled delta-slope system was monitored at high resolution. This allows development of process-based theory for the response of SRS to external forcings at the land-ocean interface. Connection between these environments was promoted with input conditions that generated plunging hyperpycnal flows at river mouths. The experiment had three stages, which included: (1) a delta-slope system aggrading with no sea level cycles, (2) a system responding to low magnitude and high frequency sea level cycles, and (3) a system responding to a high magnitude and long period cycle. All stages shared an identical background pseudosubsidence rate. Here the magnitudes and periods of sea level cycles are discussed relative to key autogenic scales. I find that, on average, sediment transport to the marine is promoted during lowstand conditions in all stages. However, the scale of the sea level cycles with respect to emergent autogenic scales controls the predictability of this response, with greater stochasticity and thus lower predictability for the response to smaller and shorter sea level cycles. Analysis of two SRS suggests that predictable responses can require sea level cycle amplitudes greater than 50 m and periods longer than 200 kyrs, but will vary with system size.

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“…However, the presence of internal fan organization can make this signal bump difficult to detect (Burgess et al, 2019). This is supported by research that suggests bulk external signals can be modulated or entirely 'shredded' by internal processes (Jerolmack and Paola, 2010;Wang et al, 2011;Romans et al, 2016;Harris et al, 2018). In some cases, however, internal processes may amplify external signals creating positive feedback loops, such as increasing channel incision on a slope due to flow confinement within the channel (Hodgson et al, 2016;de Leeuw et al, 2018a).…”

mentioning

confidence: 98%

Entangled external and internal controls on submarine fan evolution: an experimental perspective

Ferguson

Kane

Eggenhuisen

et al. 2020

The Depositional Record

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Submarine fans are formed by sediment‐laden flows shed from continental margins into ocean basins. Their morphology represents the interplay of external controls such as tectonics, climate and sea level with internal processes including channel migration and lobe compensation. However, the nature of this interaction is poorly understood. Physical modelling was used to represent the evolution of a natural‐scale submarine fan deposited during an externally forced waxing‐to‐waning sediment supply cycle. This was achieved by running five successive experimental turbidity currents with incrementally increasing then decreasing sediment supply rates. Deposits built upon the deposits of earlier flows and the distribution of erosion and deposition after each flow was recorded using digital elevation models. Initially, increasing sediment supply rate (waxing phase) led to widening and deepening of the slope channel, with basin‐floor deposits compensationally stepping forwards into the basin, favouring topographic lows. When sediment supply rate was decreased (waning phase), the slope‐channel filled as the bulk of the deposit abruptly back‐stepped due to interaction with depositional topography. Therefore, despite flows in the waxing and waning phases of sediment supply having nominally identical input conditions (i.e. sediment concentration, supply rate, grain size, etc.), depositional relief led to development of markedly different deposits. This demonstrates how external controls can be preserved in the depositional record through the progradation of basin floor deposits but that internal processes such as compensational stacking progressively obscure this signal through time. This evolution serves as an additional potential mechanism to explain commonly observed coarsening and thickening‐upwards lobe deposits, with abrupt transition to thin fine‐grained deposits. Meanwhile within the slope channel, external forcing was more readily detectable through time, with less internally driven reorganization. This validates many existing conceptual models and outcrop observations that channels are more influenced by external forcing whilst internal processes dominate basin floor lobe deposits in submarine fans.

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A Poor Relationship Between Sea Level and Deep-Water Sand Delivery

Cited by 25 publications

References 48 publications

Accommodation- versus supply-dominated systems for sediment partitioning to deep water

Accommodation- versus supply-dominated systems for sediment partitioning to deep water

Morphodynamics and Stratigraphic Architecture of Shelf-Edge Deltas Subject to Constant vs. Dynamic Environmental Forcings: A Laboratory Study

Entangled external and internal controls on submarine fan evolution: an experimental perspective

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