Constraints on mantle viscosity and Laurentide ice sheet evolution from pluvial paleolake shorelines in the western United States

Austermann, Jacqueline; Chen, Christine Y.; Lau, H. C. P.; Maloof, Adam C.; Latychev, Konstantin

doi:10.1016/j.epsl.2019.116006

Cited by 14 publications

(13 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is of great importance that seismic tomography be used in combination with flexural studies to understand the structure of continental lithosphere, because estimates of T e that are consistent with the thickness of the mechanically competent upper crust cannot be used independently to discriminate between a jelly sandwich and a crème brûlée configuration (Burov, 2015). For example, seismic tomography indicates that old, cold, and thick mantle lithosphere does not exist at Lake Bonneville (Austermann et al., 2019; Shen et al., 2013). We propose that the presence of a weak lower crust could be partially responsible for the low inferred values of T e at coronae (Russell & Johnson, 2021) despite the stagnant‐lid convection style of Venus, but future missions will be required to test this hypothesis using seismic tomography.…”

Section: Discussionmentioning

confidence: 99%

Effects of a Weak Lower Crust on the Flexure of Continental Lithosphere

Bellas

Zhong

2021

JGR Solid Earth

View full text Add to dashboard Cite

The rheology of continental lithosphere controls seismicity, orogeny, basin-formation in continents, and is partially responsible for the bimodal recycling of Earth's surface wherein continental lithosphere may be older than several Ga while oceanic lithosphere is generally younger than 200 Ma. Because of the sensitivity of lithospheric rheology to temperature and composition, increased crustal thickness may give rise to an intermediate weak layer (i.e., weak lower crust) (Bird, 1991;Chen & Molnar, 1983), which may have a significant impact on the tectonics of orogenic regions such as Tibet (Clark & Royden, 2000;Royden et al., 1997). Lithospheric rheology is frequently investigated in mineral physics experiments (Goetze & Evans, 1979) and inferred from field observations of radial seismic anisotropy (e.g., Shapiro et al., 2004) and surface wave tomography (Shen et al., 2013) which show that crustal rocks (e.g., quartz, diabase) may become extremely weak for conditions under which adjacent lithospheric mantle rocks remain much stronger (e.g., olivine). Lithospheric rheology is also frequently constrained by observations of flexure in response to surface loads such as mountains ranges, plateaus, basins, and glacial isostatic adjustment (Watts, 2001). However, it is not necessarily clear what effects an intermediate weak layer may have on lithospheric flexure and what

show abstract

Section: Discussionmentioning

confidence: 99%

Effects of a Weak Lower Crust on the Flexure of Continental Lithosphere

Bellas

Zhong

2021

JGR Solid Earth

View full text Add to dashboard Cite

show abstract

“…Viscoelastic relaxation of 2–3 mm/yr from two normal fault earthquakes ( M w 7.3, 6.8) were observed using Interferometric Synthetic Aperture Radar (Gourmelen & Amelung, 2005). Separating lake rebound uplift from post‐seismic signal will be particularly useful in providing additional constraints for upper mantle viscosity and shape of Laurentide ice sheet in the WUSA, as demonstrated recently by Austermann et al (2020) for example.…”

Section: Resultsmentioning

confidence: 89%

Present‐Day Crustal Vertical Velocity Field for the Contiguous United States

2020

View full text Add to dashboard Cite

The study of vertical crustal motion in the contiguous United States (CONUS) has traditionally focused on the high-amplitude deformation caused by glacial isostatic adjustment. To better understand more subtle vertical crustal motion resulting from other geophysical processes, we take advantage of the ongoing expansion of continuous Global Positioning System (GPS) networks, whose geodetic observations provide ever-increasing accuracy and spatial resolution of surface deformation. Using position data for 2,782 GPS stations operating between 2007 and 2017, we produce a new vertical crustal velocity field for the CONUS region. We estimate our own station velocities to ensure consistent treatment of time series outliers, noise, and offsets, and we use adaptive smoothing and interpolation to account for spatially varying station density. Our velocity field reveals spatially coherent vertical features that are representative of regional tectonics, hydrologic, and anthropogenic processes. By removing the effects of modeled glacial isostatic adjustment and hydrologic loading estimated from Gravity Recovery and Climate Experiment (GRACE) data, we reduce the variance in our velocity field by 36% and show residuals potentially due to geocenter motion and underlying tectonics.

show abstract

“…If the full‐spectrum model is incomplete, these kinds of nonlinear effects may be implicated. For example, the variations in plate thickness needed to fit the long‐term isostatic response to Lake Bonneville (Austermann et al, 2020) discussed in section 1 appear to be larger than the 30% reduction in plate thickness from the seismic to convection timescale. This difference could be due to an incompleteness in the full‐spectrum mechanical model.…”

Section: Discussionmentioning

confidence: 99%

“…More specifically, LAB depths across western North America from lake rebound processes (acting on timescales ∼100 yr) suggest a thin, high viscosity lid of 15–25 km within the vicinity of Lake Bonneville (Austermann et al, 2020) in contrast to the seismically inferred thickness of ∼80 km (Hopper & Fischer, 2018). In the colder, tectonically stable eastern part of North America, modeling glacial rebound induced by the melting of the Laurentide ice sheet from the last glacial maximum (∼25,000 yr BP) to present day using a lithosphere with a thickness of ∼100 km reproduces uplift rates across the Hudson Bay region (e.g., Lau et al, 2016), whereas seismically derived estimates suggest a LAB depth of >200 km across the same region (e.g., Conrad & Lithgow‐Bertelloni, 2006).…”

Section: Introductionmentioning

confidence: 99%

Toward a Self‐Consistent Characterization of Lithospheric Plates Using Full‐Spectrum Viscoelasticity

2020

Self Cite

View full text Add to dashboard Cite

Determining the thickness of the lithosphere in any given setting combines uncertainty in both the observational method and laboratory-derived understanding of mantle rheology. The many observational and modeling criteria across geophysical subfields for plate thickness lead to significant differences in plate thickness estimates depending on the process of interest, be it seismic wave propagation or relaxation in response to changes in loads-from earthquakes, ice sheets to volcanoes-or convection. This paper proposes a framework in which to model and interpret upper mantle mechanical structure smoothly across the full spectrum of geophysical timescales. We integrate viscous, elastic, and linear anelastic constitutive models and calculate the mechanical response from convective to seismic wave timescales (i.e., 0 to infinite frequency or, in practice, 10 −15 to 1 Hz). We apply these calculations to 1-D thermal structures and determine the normalized complex viscosity, a quantity that shows clearly the role of transient creep in weakening rock relative to the associated Maxwell rheology. Using various criteria for the lithosphere-asthenosphere boundary, we show that the apparent plate thickness will be thicker at higher frequencies than at lower frequencies. Additional calculations for nonlinear Maxwell behavior (dislocation mechanisms) demonstrate significant changes in the apparent plate structure, decreasing the long-term plate thickness, consistent with observations. Other effects such as dislocation damping (associated with a steady-state dislocation structure), melt, water, major element composition, and grain size are not included here but, when incorporated into this framework, will significantly change the full-spectrum plate thickness predictions. Plain Language Summary On Earth, broken, rigid tectonic plates lie atop slowly flowing mantle rock (over millions to billions of years). A basic understanding of the global variation in thickness of this rigid lid provides the foundation to many geodynamical predictions. However, using different techniques to estimate its thickness, for example, seismic wave propagation (acting on timescales of seconds), to the warping of plates under the weight of volcanoes (acting on timescales of millions of years) reveals many inconsistencies. At the heart of these inconsistencies is the fact that rock deforms differently to forces acting on different timescales. At very fast timescales rock deforms like an elastic solid, but at much longer timescales, rock flows. To resolve these inconsistencies, we attempt to coherently tie these disparate observations together to reach a more holistic understanding of plate thickness, accounting for these timescale effects. By incorporating current understanding on rock deformation from laboratory experiments, we demonstrate that on fast timescales (of the seismic waves used to image the Earth's interior), tectonic plates appear significantly thicker than the true thickness at million-to billion-year timescales of plate tectonics. This d...

show abstract

Constraints on mantle viscosity and Laurentide ice sheet evolution from pluvial paleolake shorelines in the western United States

Cited by 14 publications

References 52 publications

Effects of a Weak Lower Crust on the Flexure of Continental Lithosphere

Effects of a Weak Lower Crust on the Flexure of Continental Lithosphere

Present‐Day Crustal Vertical Velocity Field for the Contiguous United States

Toward a Self‐Consistent Characterization of Lithospheric Plates Using Full‐Spectrum Viscoelasticity

Contact Info

Product

Resources

About