Early Eocene Compressional Deformation in the Northeastern Tibetan Plateau Recorded by Magnetic Fabrics of the Longzhong Basin
Abstract
Intracontinental deformation records how early Eocene India-Asia collisional stress propagated into continental interiors. How rapidly compression reached the far field, and whether coeval Paleo-Pacific slab dynamics contributed, remain debated. The Longzhong Basin, ∼1,900 km north of the collisional zone, provides a key test. Yet its early tectonic regime is contested because direct strain records are scarce. Here, we applied anisotropy of magnetic susceptibility, corrected using vertical-axis rotation, to Cretaceous-early Eocene strata of the Xining and Linxia sub-basins. Cretaceous fabrics define broadly E-W K1 orientations with ambiguous kinematic significance, whereas early Eocene fabrics consistently record layer-parallel shortening. This contrast indicates that collisional compression reached the northeastern Tibetan Plateau within a few million years of collision onset. By the early Eocene, India-Asia convergence, rather than Paleo-Pacific rollback, dominated deformation in the Longzhong region, implying efficient stress transfer through mechanically coupled Tibetan terranes.
Plain Language SummaryThe India-Asia collision began sometime between about 60 and 50 million years ago, but how quickly its compressional stress reached the continental interior remains debated. We studied this question in the Longzhong Basin of the northeastern Tibetan Plateau, about 1,900 km from the collision zone. Fine-grained rocks can preserve a magnetic record of weak deformation because mineral grains subtly align during burial and tectonic squeezing. We measured this magnetic alignment and corrected it for later basin rotation. Cretaceous rocks record an east-west strain axis whose tectonic meaning is ambiguous. In contrast, early Eocene rocks, about 50 million years old, clearly record horizontal shortening. This shows that stress from the India-Asia collision reached the northeastern Tibetan Plateau within a few million years of collision onset, faster than expected from a slow, stepwise northward spread of deformation. By then, collision from the south, rather than Paleo-Pacific slab rollback to the east, was the dominant influence on deformation in the Longzhong region.
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BibTeX
@article{feng2026early,
title = {{Early Eocene Compressional Deformation in the Northeastern Tibetan Plateau Recorded by Magnetic Fabrics of the Longzhong Basin}},
author = {Zhantao Feng and Niels Meijer and Weilin Zhang and Guillaume Dupont‐nivet and Wanlong Xu and Tao Zhang and Jinbo Zan and Yibo Yang and Xiaomin Fang},
journal = {Geophysical Research Letters},
year = {2026},
month = oct,
doi = {10.1029/2026gl125250},
url = {https://hal.science/hal-05774944v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Early Eocene Compressional Deformation in the Northeastern Tibetan Plateau Recorded by Magnetic Fabrics of the Longzhong Basin
AU - Zhantao Feng
AU - Niels Meijer
AU - Weilin Zhang
AU - Guillaume Dupont‐nivet
AU - Wanlong Xu
AU - Tao Zhang
AU - Jinbo Zan
AU - Yibo Yang
AU - Xiaomin Fang
PY - 2026
DA - 2026/10/02
JO - Geophysical Research Letters
DO - 10.1029/2026gl125250
UR - https://hal.science/hal-05774944v1
AB - Intracontinental deformation records how early Eocene India-Asia collisional stress propagated into continental interiors. How rapidly compression reached the far field, and whether coeval Paleo-Pacific slab dynamics contributed, remain debated. The Longzhong Basin, ∼1,900 km north of the collisional zone, provides a key test. Yet its early tectonic regime is contested because direct strain records are scarce. Here, we applied anisotropy of magnetic susceptibility, corrected using vertical-axis rotation, to Cretaceous-early Eocene strata of the Xining and Linxia sub-basins. Cretaceous fabrics define broadly E-W K1 orientations with ambiguous kinematic significance, whereas early Eocene fabrics consistently record layer-parallel shortening. This contrast indicates that collisional compression reached the northeastern Tibetan Plateau within a few million years of collision onset. By the early Eocene, India-Asia convergence, rather than Paleo-Pacific rollback, dominated deformation in the Longzhong region, implying efficient stress transfer through mechanically coupled Tibetan terranes. Plain Language SummaryThe India-Asia collision began sometime between about 60 and 50 million years ago, but how quickly its compressional stress reached the continental interior remains debated. We studied this question in the Longzhong Basin of the northeastern Tibetan Plateau, about 1,900 km from the collision zone. Fine-grained rocks can preserve a magnetic record of weak deformation because mineral grains subtly align during burial and tectonic squeezing. We measured this magnetic alignment and corrected it for later basin rotation. Cretaceous rocks record an east-west strain axis whose tectonic meaning is ambiguous. In contrast, early Eocene rocks, about 50 million years old, clearly record horizontal shortening. This shows that stress from the India-Asia collision reached the northeastern Tibetan Plateau within a few million years of collision onset, faster than expected from a slow, stepwise northward spread of deformation. By then, collision from the south, rather than Paleo-Pacific slab rollback to the east, was the dominant influence on deformation in the Longzhong region.
SN - 0094-8276
SN - 1944-8007
ER -