Stable isotope‐based paleoaltimetry,

Abstract The quantitative estimation of paleoaltitude has become an increasing focus of Earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts, as well as the influence of mountain belt growth on regional and global climate. The general observation of decreasing δ 18 O and δ 2 H values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation. These studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming. In this review we provide a theory behind the application of stable isotope-based approaches to paleoaltimetry. We apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations. Examples of the application of paleoaltimetry techniques to Himalaya-Tibet and the Andes are discussed with implications for processes that cause surface uplift

Rise of the Andes

The surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening, leading to their gradual rise. Recent studies of the Andes indicate that their elevation remained relatively stable for long periods (tens of millions of years), separated by rapid (1 to 4 million years) changes of 1.5 kilometers or more. Periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable, dense lower lithosphere after long-term thickening of the crust and lithospheric mantle

Rapid regional surface uplift of the northern Altiplano plateau revealed by multiproxy paleoclimate reconstruction

The central Altiplano is inferred to have experienced ∼2.5±1km surface uplift between ∼10 and 6 Ma, while the southern Altiplano experienced a similar magnitude of surface uplift that began earlier, between ∼16 and 9 Ma. To properly constrain the along strike timing of the Altiplano plateau surface uplift, it is necessary to know how and when the northernmost part of the Altiplano plateau evolved. We reconstruct the paleoclimate and infer the corresponding paleoelevation from the Miocene–Pliocene deposits of the Descanso–Yauri basin (14–15°S) in the northernmost part of the Altiplano plateau using 4 different proxies, including carbonate clumped isotope composition (i.e., Δ_(47) values), carbonate δ^(18)O_c, leaf wax δD_(wax) and pollen assemblages from paleosol, lacustrine and palustrine carbonates and organic-rich sediments. The isotopic signatures reflect past climate conditions of mean annual air temperature (Δ_(47)) and meteoric water isotope values (δ^(18)O_c, δD_(wax)). Our results show that the northernmost plateau remained at low elevation (0.9±0.8 to 2.1±0.9km) until late Miocene time (∼9 Ma) characterized by ∼15 °C warmer than modern temperature (mean annual air temperature of 23±4°C, 2σ), low elevation vegetation and precipitation signature with reconstructed □ δ^(18)O_(mw) (VSMOW) of −8.3±2.0‰(2σ) from carbonate (δ^(18)O_c) and −8.6±1.8‰(2σ) from leaf wax (δD_(wax)). Modern elevations of 4 km were not reached until 5.4±1.0Ma, as indicated by a negative shift in δD_(wax) (VSMOW) from −143.4±12.8‰(2σ) to −209.2±21.1‰(2σ) between 9.1±0.7 and 5.4±1.0Ma. The timing of surface uplift of the northernmost Altiplano is consistent with the evidence for late Miocene surface uplift of the central Altiplano (16–19°S) between 10 and 6 Ma, and indicates that regional scale uplift in the northern–central plateau significantly postdates the onset of surface uplift in the southern Altiplano (19–22°S) between ∼16 and 9 Ma. These results are consistent with piecemeal removal of the lower dense lithosphere, combined with possible lower/middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the Altiplano plateau

Dominant 100,000-year precipitation cyclicity in a late Miocene lake from northeast Tibet

East Asian summer monsoon (EASM) precipitation received by northern China over the past 800 thousand years (ky) is characterized by dominant 100-ky periodicity, mainly attributed to CO2 and Northern Hemisphere insolation–driven ice sheet forcing. We established an EASM record in the Late Miocene from lacustrine sediments in the Qaidam Basin, northern China, which appears to exhibit a dominant 100-ky periodicity similar to the EASM records during the Late Quaternary. Because evidence suggests that partial or ephemeral ice existed in the Northern Hemisphere during the Late Miocene, we attribute the 100-ky cycles to CO2 and Southern Hemisphere insolation–driven Antarctic ice sheet forcing. This indicates a >6–million year earlier onset of the dominant 100-ky Asian monsoon and, likely, glacial and CO2 cycles and may indicate dominant forcing of Northern Hemisphere climate by CO2 and Southern Hemisphere ice sheets in a warm world.This work was funded by the national key research and development program of China (2016YFE0109500), the (973) National Basic Research Program of China (grant no. 2013CB956400), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant no. XDB03020400), the National Natural Science Foundation of China (grant nos. 41422204, 41172329, and 41290253), and the U.S. NSF (grant no. 1545859)

Rapid regional surface uplift of the northern Altiplano plateau revealed by multiproxy paleoclimate reconstruction

The central Altiplano is inferred to have experienced ∼2.5±1km surface uplift between ∼10 and 6 Ma, while the southern Altiplano experienced a similar magnitude of surface uplift that began earlier, between ∼16 and 9 Ma. To properly constrain the along strike timing of the Altiplano plateau surface uplift, it is necessary to know how and when the northernmost part of the Altiplano plateau evolved. We reconstruct the paleoclimate and infer the corresponding paleoelevation from the Miocene–Pliocene deposits of the Descanso–Yauri basin (14–15°S) in the northernmost part of the Altiplano plateau using 4 different proxies, including carbonate clumped isotope composition (i.e., Δ_(47) values), carbonate δ^(18)O_c, leaf wax δD_(wax) and pollen assemblages from paleosol, lacustrine and palustrine carbonates and organic-rich sediments. The isotopic signatures reflect past climate conditions of mean annual air temperature (Δ_(47)) and meteoric water isotope values (δ^(18)O_c, δD_(wax)). Our results show that the northernmost plateau remained at low elevation (0.9±0.8 to 2.1±0.9km) until late Miocene time (∼9 Ma) characterized by ∼15 °C warmer than modern temperature (mean annual air temperature of 23±4°C, 2σ), low elevation vegetation and precipitation signature with reconstructed □ δ^(18)O_(mw) (VSMOW) of −8.3±2.0‰(2σ) from carbonate (δ^(18)O_c) and −8.6±1.8‰(2σ) from leaf wax (δD_(wax)). Modern elevations of 4 km were not reached until 5.4±1.0Ma, as indicated by a negative shift in δD_(wax) (VSMOW) from −143.4±12.8‰(2σ) to −209.2±21.1‰(2σ) between 9.1±0.7 and 5.4±1.0Ma. The timing of surface uplift of the northernmost Altiplano is consistent with the evidence for late Miocene surface uplift of the central Altiplano (16–19°S) between 10 and 6 Ma, and indicates that regional scale uplift in the northern–central plateau significantly postdates the onset of surface uplift in the southern Altiplano (19–22°S) between ∼16 and 9 Ma. These results are consistent with piecemeal removal of the lower dense lithosphere, combined with possible lower/middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the Altiplano plateau

Joint insolation and ice sheet/CO2 forcing on northern china precipitation during pliocene warmth

We demonstrate that the precipitation record on the Chinese Loess Plateau during the middle Piacenzian (3.264–3.025 Ma) has strong 20-kyr precessional cycles, challenging past knowledge about East Asian monsoon variations at the orbital timescales

The growth of northeastern Tibet and its relevance to large-scale continental geodynamics: A review of recent studies

Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10–20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation

Tectonic and paleoelevation history of the Thakkhola Graben and implications for the evolution of the southern Tibetan Plateau

Sediment accumulation in extensional basins in the Tibetan Plateau records tectonic processes and paleoenvironments on the plateau. It is generally assumed that extension on the plateau took place during uplift of the plateau. Based on this assumption, several studies have been aimed at determining the timing of extensional basin development as a proxy for the timing of uplift of the plateau. This dissertation documents the sedimentology of the N-trending Thakkhola graben in the southern Tibetan Plateau in an attempt to test various models for the timing and mechanisms of uplift of the plateau. Magnetostratigraphic and stable carbon isotopic age constraints indicate that deposition in the Thakkhola graben occurred during the Late Miocene (∼11 Ma) to Pliocene. The oxygen isotopic composition of carbonate rocks deposited in the basin records the isotopic composition of paleometeoric water that fell in the basin and in flanking drainages when the carbonate was precipitating. Carbonate oxygen isotopes indicate high-elevation rainfall in the basin, consistent with modern elevations since the onset of deposition in the basin. This implies that the average elevation in the Thakkhola graben has been >4,500 m since it began to form. Lateral facies changes, conglomerate provenance, and paleocurrent data document significant displacement on the western basin-bounding fault since deposition began in the basin. By Pliocene time, a large, southward axial drainage had developed that was similar in size to the modern Kali Gandaki River, which drains the southern plateau, through the Thakkhola graben and Himalayan fold-thrust belt to the south. Change in environments of deposition in the Thakkhola graben indicates trends toward an increasingly arid climate through time. This climate change is documented throughout south Asia and possibly Tibet between ∼8 and 7 Ma and have been assumed to reflect uplift of the plateau. However, high elevation in the Thakkhola graben since ∼11 Ma challenges these commonly held notions

How I Teach: Carmala Garzione

Carmala Garzione is a member of the Department of Earth and Environmental Science