Role of source-layer tilts in the axi-asymmetric growth of diapirs triggered by a Rayleigh–Taylor instability

Dutta, Urmi; Baruah, Amiya; Mandal, Nibir

doi:10.1093/gji/ggw244

Cited by 13 publications

(7 citation statements)

References 73 publications

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“…Modelling in two dimensions also assumes that all processes (such as salt withdrawal and stratigraphic bed rotation) are equal in all directions, which is an oversimplification (e.g. Dutta et al., 2016; Ismail‐Zadeh et al., 2004; Jackson & Hudec, 2017; Mattson et al., 2020; Pichel & Jackson, 2020). However, this is a suitable assumption in simple models that focus primarily on the role of sedimentation rate variability on the halokinetic depositional record.…”

Section: Methodsmentioning

confidence: 99%

Halokinetic modulation of sedimentary thickness and architecture: A numerical modelling approach

et al. 2021

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Subsurface salt flow can deform overlying strata and influence contemporaneous sedimentary systems. Studying salt‐sediment interactions is challenging in the subsurface due to poor imaging adjacent to salt, and in the field due to the dissolution of halite. Discrete Element Modelling provides an efficient and inexpensive tool to model stratigraphy and deformation around salt structures, which is advantageous over other modelling techniques as it realistically recreates brittle processes such as faulting. Six 2D experiments were run representing 4.6 Myr to determine the effect of salt growth on syn‐kinematic stratigraphy. Halokinetic deformation of stratigraphic architecture was assessed by varying sediment input rates through time. Results show the realistic formation and evolution of salt‐related faults which define a zone of halokinetic influence ca. 3 times the width of the initial diapir. Outside of this, early diapiric and syn‐kinematic stratigraphy are undeformed. Within this zone, syn‐kinematic strata are initially isolated into primary salt withdrawal basins, onlapping and thinning towards the salt‐cored high. In most models, syn‐kinematic strata eventually thin across and cover the diapir roof. Thinning rates are up to six times greater within 350 m of the diapir, compared to further afield, and typically decrease upwards (with time) and laterally (with distance) from the diapir. Outputs are compared to a subsurface example from the Pierce field, UK North Sea, which highlights the importance of considering local fluctuations in diapir rise rate. These can create stratigraphic architectures that may erroneously be interpreted to represent increases/decreases in sedimentation rate. Exposed examples, such as the Bakio diapir, northern Spain, can be used to make inferences of the expected depositional facies, below model resolution. Our models aid the prediction of sedimentary unit thickness and thinning rates and can be used to test interpretations arising from incomplete or low‐resolution subsurface and outcrop data when building geological models for subsurface energy.

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Section: Methodsmentioning

confidence: 99%

Halokinetic modulation of sedimentary thickness and architecture: A numerical modelling approach

et al. 2021

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“…We have implemented the VOF method using the CFD code of FLUENT [28,29]. In our previous study [6], we performed the validation of this code for Rayleigh-Taylor instabilities, applicable to large-scale geodynamic flows.…”

Section: The Vof Methodsmentioning

confidence: 99%

“…However, in some geodynamic settings, e.g. subduction zones plumes are driven by compositional buoyancy forces [5,6]. Irrespective of their driving mechanism, plumes typically show bulbous heads trailing into slender, cylindrical tails.…”

Section: Introductionmentioning

confidence: 99%

Pulsating dynamics of thermal plumes and its implications for multiple eruption events in the Deccan Traps, India

Dutta,

Mandal

2017

Preprint

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In Earth's mantle gravity instabilities initiated by density inversion lead to upwelling of hot materials as plumes. This study focuses upon the problem of their ascent dynamics to provide an explanation of the periodic multiple eruption events in large igneous provinces and hotspots. We demonstrate from physical experiments that plumes can ascend in a continuous process to form a single large head trailing into a long slender tail, typically described in the literature only under specific physical conditions. Alternatively, they ascend in a pulsating fashion, and produce multiple in-axis heads of varying dimensions. Based on the Volume of Fluid (VOF) method, we performed computational fluid dynamics (CFD) simulations to constrain the thermo-mechanical conditions that decide the continuous versus pulsating dynamics. Our CFD simulations suggest the density (ρ * ) and the viscosity (R) ratios of the ambient to the plume materials and the influx rates (Re) are the prime factors in controlling the ascent dynamics. Conditions with large R (>50) develop pulsating plumes, which are sustained preferentially under low ρ * and Re conditions. Again, the increasing temperature difference between the plume and the ambient medium is found to promote pulsating behaviour. From these CFD simulations we show the thermal structures of a plume, and predict the peak thermal events near the surface that commence periodically as pulses with a time interval of 1.4-3 Ma. The pulsating plume model explains the multiple eruption events in the Deccan Traps in India, where the time scale of their intervals estimated from the available 40 Ar/ 39 Ar geochronological data shows an excellent match with our simulation results.

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“…These equations were solved using commercial finite element code (COMSOL Multiphysics, 2015) (details given in supporting information Sections S8 and S9). Several earlier workers used this code for large‐scale modeling in geodynamics (Dutta et al, 2016; He, 2014; Ryu & Lee, 2017). We ran two types of CFD simulations: (1) models with dimensions and material parameters, corresponding to the laboratory setup and (2) models approximated to the natural prototype.…”

Section: Cfd Simulationsmentioning

confidence: 99%

Cold Plumes Initiated by Rayleigh‐Taylor Instabilities in Subduction Zones, and Their Characteristic Volcanic Distributions: The Role of Slab Dip

et al. 2020

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Dehydration melting in subduction zones often produces cold plumes, initiated by Rayleigh‐Taylor instabilities in the buoyant partially molten zones lying above the dipping subducting slabs. We use scaled laboratory experiments to demonstrate how the slab dip (α) can control the evolution of such plumes. For α > 0°, Rayleigh‐Taylor instabilities evolve as two orthogonal waves, one trench perpendicular with wavelength λL and the other one trench parallel with wavelength λT (λT > λL). We show that two competing processes, (1) λL‐controlled updip advection of partially molten materials and (2) λT/λL interference, determine the modes of plume growth. The λT/λL interference gives rise to an areal distribution of plumes (Mode 1), whereas advection leads to a linear distribution of plumes (Mode 2) at the upper fringe of the partially molten layer. The λT wave instabilities do not grow when α exceeds a threshold value (α* = 30°). For α > α*, λL‐driven advection takes the control to produce exclusively Mode 2 plumes. We performed a series of 2‐D and 3‐D computational fluid dynamics simulations to test the criticality of slab dip in switching the Mode 1 to Mode 2 transition at α*. We discuss the effects of viscosity ratio (R) and the density contrast (Δρ) between the source layers and ambient mantle, source layer thickness (Ts), and slab velocity (Us) on the development of cold plumes. Finally, we discuss the areal versus linear distributions of volcanoes from natural subduction zones as possible examples of Mode 1 versus Mode 2 plume products.

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Role of source-layer tilts in the axi-asymmetric growth of diapirs triggered by a Rayleigh–Taylor instability

Cited by 13 publications

References 73 publications

Halokinetic modulation of sedimentary thickness and architecture: A numerical modelling approach

Halokinetic modulation of sedimentary thickness and architecture: A numerical modelling approach

Pulsating dynamics of thermal plumes and its implications for multiple eruption events in the Deccan Traps, India

Cold Plumes Initiated by Rayleigh‐Taylor Instabilities in Subduction Zones, and Their Characteristic Volcanic Distributions: The Role of Slab Dip

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