Fuller
Dorian Q.
Fuller
Dorian Q.
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ArticleShort communication : Massive erosion in monsoonal central India linked to late Holocene land cover degradation(Copernicus Publications on behalf of the European Geosciences Union, 2017-12-01) Giosan, Liviu ; Ponton, Camilo ; Usman, Muhammed ; Blusztajn, Jerzy S. ; Fuller, Dorian Q. ; Galy, Valier ; Haghipour, Negar ; Johnson, Joel E. ; McIntyre, Cameron P. ; Wacker, Lukas ; Eglinton, Timothy I.Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.
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ArticleHolocene evolution in weathering and erosion patterns in the Pearl River delta(John Wiley & Sons, 2013-07-26) Hu, Dengke ; Clift, Peter D. ; Boning, Philipp ; Hannigan, Robyn E. ; Hillier, Stephen ; Blusztajn, Jerzy S. ; Wan, Shiming ; Fuller, Dorian Q.Sediments in the Pearl River delta have the potential to record the weathering response of this river basin to climate change since 9.5 ka, most notably weakening of the Asian monsoon since the Early Holocene (∼8 ka). Cores from the Pearl River delta show a clear temporal evolution of weathering intensity, as measured by K/Al, K/Rb, and clay mineralogy, that shows deposition of less weathered sediment at a time of weakening monsoon rainfall in the Early-Mid Holocene (6.0–2.5 ka). This may reflect an immediate response to a less humid climate, or more likely reduced reworking of older deposits from river terraces as the monsoon weakened. Human settlement of the Pearl River basin may have had a major impact on landscape and erosion as a result of the establishment of widespread agriculture. After around 2.5 ka weathering intensity sharply increased, despite limited change in the monsoon, but at a time when anthropogenic pollutants (e.g., Cu, Zn, and Pb) increased and when the flora of the basin changed. 87Sr/86Sr covaries with these other proxies but is also partly influenced by the presence of carbonate. The sediments in the modern Pearl River are even more weathered than the youngest material from the delta cores. We infer that the spread of farming into the Pearl River basin around 2.7 ka was followed by a widespread reworking of old, weathered soils after 2.5 ka, and large-scale disruption of the river system that was advanced by 2.0 ka.
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ArticleNeoglacial climate anomalies and the Harappan metamorphosis(Copernicus Publications on behalf of the European Geosciences Union, 2018-11-13) Giosan, Liviu ; Orsi, William D. ; Coolen, Marco J. L. ; Wuchter, Cornelia ; Dunlea, Ann G. ; Thirumalai, Kaustubh ; Munoz, Samuel E. ; Clift, Peter D. ; Donnelly, Jeffrey P. ; Galy, Valier ; Fuller, Dorian Q.Climate exerted constraints on the growth and decline of past human societies but our knowledge of temporal and spatial climatic patterns is often too restricted to address causal connections. At a global scale, the inter-hemispheric thermal balance provides an emergent framework for understanding regional Holocene climate variability. As the thermal balance adjusted to gradual changes in the seasonality of insolation, the Intertropical Convergence Zone migrated southward accompanied by a weakening of the Indian summer monsoon. Superimposed on this trend, anomalies such as the Little Ice Age point to asymmetric changes in the extratropics of either hemisphere. Here we present a reconstruction of the Indian winter monsoon in the Arabian Sea for the last 6000 years based on paleobiological records in sediments from the continental margin of Pakistan at two levels of ecological complexity: sedimentary ancient DNA reflecting water column environmental states and planktonic foraminifers sensitive to winter conditions. We show that strong winter monsoons between ca. 4500 and 3000 years ago occurred during a period characterized by a series of weak interhemispheric temperature contrast intervals, which we identify as the early neoglacial anomalies (ENA). The strong winter monsoons during ENA were accompanied by changes in wind and precipitation patterns that are particularly evident across the eastern Northern Hemisphere and tropics. This coordinated climate reorganization may have helped trigger the metamorphosis of the urban Harappan civilization into a rural society through a push–pull migration from summer flood-deficient river valleys to the Himalayan piedmont plains with augmented winter rains. The decline in the winter monsoon between 3300 and 3000 years ago at the end of ENA could have played a role in the demise of the rural late Harappans during that time as the first Iron Age culture established itself on the Ghaggar-Hakra interfluve. Finally, we speculate that time-transgressive land cover changes due to aridification of the tropics may have led to a generalized instability of the global climate during ENA at the transition from the warmer Holocene thermal maximum to the cooler Neoglacial.
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ArticleHolocene aridification of India(American Geophysical Union, 2012-02-14) Ponton, Camilo ; Giosan, Liviu ; Eglinton, Timothy I. ; Fuller, Dorian Q. ; Johnson, Joel E. ; Kumar, Pushpendra ; Collett, Timothy S.Spanning a latitudinal range typical for deserts, the Indian peninsula is fertile instead and sustains over a billion people through monsoonal rains. Despite the strong link between climate and society, our knowledge of the long-term monsoon variability is incomplete over the Indian subcontinent. Here we reconstruct the Holocene paleoclimate in the core monsoon zone (CMZ) of the Indian peninsula using a sediment core recovered offshore from the mouth of Godavari River. Carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the CMZ and document a gradual increase in aridity-adapted vegetation from ~4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants after that. The oxygen isotopic composition of planktonic foraminifer Globigerinoides ruber detects unprecedented high salinity events in the Bay of Bengal over the last 3,000 years, and especially after 1,700 years ago, which suggest that the CMZ aridification intensified in the late Holocene through a series of sub-millennial dry episodes. Cultural changes occurred across the Indian subcontinent as the climate became more arid after ~4,000 years. Sedentary agriculture took hold in the drying central and south India, while the urban Harappan civilization collapsed in the already arid Indus basin. The establishment of a more variable hydroclimate over the last ca. 1,700 years may have led to the rapid proliferation of water-conservation technology in south India.