Temporal changes in rock uplift rates of folds in the foreland of the Tian Shan and the Pamir from geodetic and geologic data

Abstract

Understanding the evolution of continental deformation zones relies on quantifying spatial and temporal changes in deformation rates of tectonic structures. Along the eastern boundary of the Pamir-Tian Shan collision zone, we constrain secular variations of rock uplift rates for a series of five Quaternary detachment-and fault-related folds from their initiation to the modern day. When combined with GPS data, decomposition of interferometric synthetic aperture radar time series constrains the spatial pattern of surface and rock uplift on the folds deforming at decadal rates of 1-5 mm/yr. These data confirm the previously proposed basinward propagation of structures during the Quaternary. By fitting our geodetic rates and previously published geologic uplift rates with piecewise linear functions, we find that gradual rate changes over >100 kyr can explain the interferometric synthetic aperture radar observations where changes in average uplift rates are greater than~1 mm/yr among different time intervals (~10 1 , 10 4-5 , and 10 5-6 years).

Variations of Lateral Bedrock Erosion Rates Control Planation of Uplifting Folds in the Foreland of the Tian Shan, NW China

“…We note that this range of incision/uplift rates is decreased by ~0.5 mm/yr for Mutule if the central age model is used for all samples (Figure ). These rates are similar to the million‐year rock‐uplift rates for the Kashi fold (Bufe et al, ; Chen et al, ;Heermance et al, ; Scharer et al, ). In contrast, rock‐uplift rates on the Atushi and Mutule folds likely decreased from rates of >3–4 mm/yr close to their initiation ~1–1.4 Myr ago, to average rates of 1–2 mm/yr over the past 30–80 kyr (Bufe et al, ).…”

“…Equations – show that in order to constrain rates of lateral planation on kiloyear timescales, rock‐uplift rates of the folds and aggradation rates in the foreland over the same kiloyear timescales have to be constrained. Since initiation of fold growth, as determined by the first appearance of growth strata 1–2.5 Myr ago, average rock‐uplift rates of the Kashi, Atushi, and Mutule folds have been constrained to 1–4 mm/yr (Bufe et al, ; Chen et al, ; Heermance et al, ). However, rock‐uplift rates over the past 30–80 kyr (the timing of the most recent fold planation episodes) remain poorly constrained.…”

“…Moreover, episodes of relative tectonic quiescence with durations of several tens of kiloyears have been interpreted on some slowly growing, thrust‐controlled anticlines (Gunderson et al, ). However, given the high average uplift rates of ≥1 mm/yr calculated across the past 30–80 kyr (Table ), the scarcity of modern seismicity on these structures (Bufe et al, ; Li et al, ), and the occurrence of multiple series of differentially uplifted terrace sequences, an intermittency of uplift rates on timescales much longer than a few kiloyears, appears unlikely. We, therefore, conclude that the terraces in the foreland of the Tian Shan record continuous uplift of the Atushi, Kashi, and Mutule folds on timescales of tens of kiloyears and at rates that are broadly comparable to million‐year averages.…”

Along‐Strike and Downdip Segmentation of the Pamir Frontal Thrust and Its Association With the 1985Mw6.9 Wuqia Earthquake

“…The MPT, the boundary fault of the Pamir range and its foreland basin, initiated in the late Oligocene‐early Miocene (Cao et al, ; Sobel et al, ; Sobel & Dumitru, ). Its Quaternary slip rate, however, appears to be quite low (<1 mm/a), such that the regional convergence is now concentrated on the PFT, lying tens of kilometers north of the MPT (Arrowsmith & Strecker, ; Bufe et al, ; T. Li et al, , ; Thompson Jobe et al, ; Zubovich et al, ). The PFT initiated approximately 5–6 Ma, representing the latest, major forelandward propagation of the Pamir (Thompson et al, ).…”

Quaternary tectonic evolution of the Pamir‐Tian Shan convergence zone, Northwest China

“…These structures commonly preserve multiple flights of terraces that permit quantification of the Quaternary spatiotemporal evolution of the deformation as the collision between the Tian Shan and Pamir progressed. We integrate our data with previous recent work in the region [ Scharer et al ., ; Chen et al ., ; Heermance et al ., ; Li , ; Li et al ., , , , ; Thompson , ; Yang , ; Bufe et al ., , ] to reconstruct Quaternary deformation patterns across the western Tarim Basin.…”