# Subduction Evolution Controlled Himalayan Orogenesis: Implications from 3-D Subduction Modeling
## 1 Introduction  
Himalayan uplift is one of the most important orogenic and climate forcing events of the Cenozoic (e.g., [1]). As the largest and most active collisional orogen at present (e.g., [2]), the Himalayas are the result of the Indian plate colliding with Eurasia, which first occurred at the center portion of the Yarlung-Tsangpo suture zone (YTSZ) between ca. 65 Ma and 63 Ma (e.g., [3]), and India continues to plunge into Eurasia along the main boundary thrust (MBT) (Figure 1). The India-Eurasia collision is characterized by a significant level of uplift, particularly along the high Himalayas, and an integral rise of the Tibetan Plateau ranging across thousands of kilometers, constituting the highest landscape on Earth in northeastern India (Figure 1). However, the way in which the historical evolution of continental subduction induces plateau uplift and the way it controls the variation in uplift between outboard and inboard areas is still unclear. The growth of Himalayan orogen was reconstructed using a paleoaltimeter based on paleoenthalpy contained in fossil leaves from two newly reported assemblages in southern Tibet (Liuqu and Qiabulin) and four previously known floras from the Himalaya foreland basin, using climate leaf analysis, multivariate program analysis, and isotopic data [4]. Zircon U-Pb dating has constrained the Liuqu flora to the latest Paleocene (ca. 56 Ma) and the Qiabulin flora to the earliest Miocene (ca. 21 Ma), the latter of which marked the starting point for a sudden change to accelerated uplift in the Himalayas. The proto-Himalayas grew slowly from \(\approx\)1000 m in the late Paleocene to Eocene (>42 Ma) to \(\approx\)2.3 km at the beginning of the Miocene (23 Ma) and reached at least 5 km by approximately 15-11 Ma (e.g., [4]). The Himalaya-Tibet edifice and the Himalayan foreland basin have been gradually drying since 56 Ma, most likely due to the Himalayan orogen's uplift [4]. To assess the role of active tectonics and geometric variations in shaping the topography of the northwestern Himalayas, new constraints on deformation over geomorphic timescales are used, including morphometric analysis using high-resolution digital elevation models and field observations of rock type (e.g., [5]). The regional distribution of topographic growth indicates consistent active growth over million-year to millennial timescales in the Himalayas with a structural and/or tectonic control on topographic evolution. With a focus on deformation restoration, [PERSON] et al. [6] estimated that at least 1630 km of shortening (along 94\({}^{\circ}\) E) has occurred between India and Asia since 55 Ma, and Asia and the Himalayas have accommodated 1010 km and 620 km of the shortening, respectively. [PERSON] et al. [7] suggested that slab break-off triggered lithosphere-asthenosphere interaction at the convergent margin. [PERSON] et al. [8] showed that the closure of the former Tethys Ocean can best be explained by asthenospheric mantle flow transporting India northward,  
Figure 1: Tectonic map of the Himalayan orogen, including the major topographic features and sutures: YTSZ, Yarlung–Tsangpo suture zone; BNSZ, Bangong–Nujiang suture zone; JRSZ, Jinsha River suture zone; EKSZ, East Kunlun suture zone; ATSZ, Altyn Tagh suture zone; KF, Karakorum fault; MBT, main boundary thrust. Dashed lines indicate the main orogenic region focused by this study. forming the Himalayas and the Tibetan Plateau, by comparing the tectonic and kinematic records from last 50 Ma with seismic tomography and anisotropy models. The 3-D evolutionary models of Himalayan orogenesis were developed, and they revealed a substantial temporal relationship between the Indian slab's southward drift, lateral migration of slab detachment, and subsequent dynamic rebound with major alteration in Himalayas and coeval monsoon intensification (e.g., [9]).