Depositional effects of flow nonuniformity and stratification within turbidity currents approaching a bounding slope; deflection, reflection, and facies variation

Kneller, Ben; McCaffrey, William D.

doi:10.2110/jsr.69.980

Cited by 234 publications

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“…Grain-size trends vertically in thePassive onlap of such a cloud will produce a lower-slope deposit with low rates of grain-size decline 612 with a more rapid fall in grain size above the zone where the concentration interface impinges on 613 the slope. Because the higher flow zone may be disturbed by internal waves, the deposit here may 614 be strongly vacillitory (e.g., exhibiting the repetitions of Kneller and McCaffrey, 1999). Where the 615 suspension partly overspills, grain-size gradients in the ponded deposit may be relatively muted (cf.…”

Section: Application To Natural Examples 495mentioning

confidence: 99%

Flow Behavior of Ponded Turbidity Currents

Patacci¹,

Haughton²,

McCaffrey³

2015

Journal of Sedimentary Research

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7Sea-floor topography can constrict, deflect, or reflect turbidity currents resulting in a range of 8 distinctive deposits. Where flows rebound off slopes and a suspension cloud collects in an enclosed 9 basin, ponded or contained turbidites are deposited. Ponded turbidites have been widely recognized 10 in slope mini-basins and on small, structurally confined basin floors in strike-slip and foreland-basin 11 settings. They can have a variable internal structure the significance of which remains poorly 12 understood in terms of flow behavior. New experiments demonstrate that the ponding process can 13 comprise up to four phases: 1) cloud establishment, 2) inflation, 3) steady-state maintenance, and 4) 14 collapse. The experiments explored the behavior of sustained turbidity currents draining into small 15 basins and show that the ponded suspensions that form are characterized by an important internal 16 interface; this divides a lower outbound-moving layer from an upper return layer. The basal layer 17 evolves to constant concentration and grain size, whereas the upper layer is graded (concentration 18 and grain size decrease upward). During the cloud inflation stage, the concentration and velocity 19 profiles of the ponded suspension evolve, and this phase can dominate the resulting deposit. 20Outbound internal waves can travel along the interface between the outbound and return layers and 21 impinge against the confining slope, and their amplitude is highest when the density contrast 22 between layers is greatest, e.g., when the input flows are thin and dense. The experiments show 23 that flow reversals can arise in several ways (initial rebound, episodic collapse of the wedge of fluid 24 above the counter slope, "grounding" of the internal velocity interface) and that despite steady 25 2 input, velocities decay and the deposit grades upwards. Internal waves emanate from the input 26 point, i.e., do not form as reflections off the counter slope. The internal grain-size interface within 27

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Section: Application To Natural Examples 495mentioning

confidence: 99%

Flow Behavior of Ponded Turbidity Currents

Patacci¹,

Haughton²,

McCaffrey³

2015

Journal of Sedimentary Research

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“…Changing topography induces specific trends in facies organization and bed sequences (e.g. Kneller & McCaffrey 1999). In this volume, using examples near Annot, MeCaffrey & Kneller identify three scales of spatial non-uniformity of turbidity currents:…”

Section: Interaction Between Turbidity Flows and Basin-floor Topographymentioning

confidence: 99%

Deep-water sedimentation in the Alpine Foreland Basin of SE France: New perspectives on the Grès d’Annot and related systems—an introduction

Joseph

Lomas²

2004

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“…Large-scale mass-wasting events can therefore modify the geometry of sedimentary basins and result in rapid shifts in the location of slope depocenters (Lucente and Pini 2008). Kneller et al (2016) further pointed out that the deflection and reflection of turbidity flows, and associated erosion, bypass and deposition processes, are controlled by: a) the scale and geometry of MTD-associated topographic relief; and b) turbidity flow properties, e.g., thickness, grain-size distribution and variation in the vertical density of flows (Kneller et al 2016;Kneller and McCaffrey 1999).…”

Section: Introductionmentioning

confidence: 99%

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

Qin

Alves

Constantine

et al. 2017

Journal of Sedimentary Research

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ABSTRACT:A Pliocene-Quaternary submarine channel system, influenced by a localized mass wasting, is investigated in this work using high-resolution 3D seismic data from offshore Espírito Santo Basin, SE Brazil. Three abandoned channels, a channel belt and an mass-transport deposit (MTD) are recognized in the channel system within a confluence region confined by salt diapirs. In this confluence region, the cross-sectional area (CSA) of the channel system can be up to 1.2 km 2 , i.e., 4 to 10 times larger than CSA in other parts of the channel system. Such significant changes in the architecture and morphology of the channel system resulted from the interaction between mass-wasting processes and turbidity flows. We postulate that a basal erosional scar was created by mass-wasting processes and was filled with an MTD. This basal scar was then used as a preferential pathway for turbidity flows, which were captured by its headwall and lateral margins. The interpreted data shows that the captured turbidity flows greatly widened the basal scar, but caused only small modifications in scar height. Part of the MTD within the basal scar was removed downslope by turbidity flows, and was replaced by channel-fill deposits. This paper shows a flow-capture process occurred in a confluence region on continental slope. Basal scars can capture turbidity flows and facilitate flow channelization, which is a key process for submarine-channel initiation. The replacement of MTD by channel-fill deposits has profound implications for reservoir volumes and net-to-gross ratios in channel systems and partly depends on the turbidity-flows properties, such as their erosive ability and frequency. The more erosive and frequent flows are captured by the basal scar, the larger is the accommodation space created for succeeding sand-prone turbidites.

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Depositional effects of flow nonuniformity and stratification within turbidity currents approaching a bounding slope; deflection, reflection, and facies variation

Cited by 234 publications

References 0 publications

Flow Behavior of Ponded Turbidity Currents

Flow Behavior of Ponded Turbidity Currents

Deep-water sedimentation in the Alpine Foreland Basin of SE France: New perspectives on the Grès d’Annot and related systems—an introduction

The Role of Mass Wasting In the Progressive Development Of Submarine Channels (Espírito Santo Basin, Se Brazil)

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