TY - GEN A1 - Sparkes, Robert B. A1 - Hovius, Niels A1 - Galy, Albert A1 - Liu, James T. T1 - Survival of graphitized petrogenic organic carbon through multiple erosional cycles T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Graphite forms the endpoint for organic carbon metamorphism; it is extremely resilient to physical, biological and chemical degradation. Carbonaceous materials (CM) contained within sediments, collected across Taiwan and from the Gaoping submarine canyon, were analyzed using Raman spectroscopy to determine the crystallinity. This allowed the erosional and orogenic movements of petrogenic organic carbon (OCpetro) during the Taiwanese orogeny to be deduced. After automatically fitting and classifying spectra, the distribution of four groups of CM within the sediments provides evidence that many forms of OCpetro have survived at least one previous cycle of erosion, transport and burial before forming rocks in the Western Foothills of the island. There is extensive detrital graphite present in rocks that have not experienced high-grade metamorphism, and graphite flakes are also found in recently deposited marine sediments off Taiwan. The tectonic and geological history of the island shows that these graphite flakes must have survived at least three episodes of recycling. Therefore, transformation to graphite during burial and orogeny is a mechanism for stabilizing organic carbon over geological time, removing biospheric carbon from the active carbon cycle and protecting it from oxidation during future erosion events. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1223 KW - graphite KW - organic carbon KW - orogeny KW - recycling KW - Raman spectroscopy KW - erosion Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-533541 SN - 1866-8372 ER - TY - JOUR A1 - Emberson, Robert A1 - Galy, Albert A1 - Hovius, Niels T1 - Weathering of Reactive Mineral Phases in Landslides Acts as a Source of Carbon Dioxide in Mountain Belts JF - Journal of geophysical research : Earth surface N2 - Bedrock landsliding in mountain belts can elevate overall chemical weathering rates through rapid dissolution of exhumed reactive mineral phases in transiently stored deposits. This link between a key process of erosion and the resultant weathering affects the sequestering of carbon dioxide through weathering of silicate minerals and broader links between erosion in active orogens and climate change. Here we address the effect on the carbon cycle of weathering induced by bedrock landsliding in Taiwan and the Western Southern Alps of New Zealand. Using solute chemistry data from samples of seepage from landslide deposits and river discharge from catchments with variable proportions of landsliding, we model the proportion of silicate and carbonate weathering and the balance of sulfuric and carbonic acids that act as weathering agents. We correct for secondary precipitation, geothermal, and cyclic input, to find a closer approximation of the weathering explicitly occurring within landslide deposits. We find highly variable proportions of sulfuric and carbonic acids driving weathering in landslides and stable hillslopes. Despite this variability, the predominance of rapid carbonate weathering within landslides and catchments where mass wasting is prevalent results at best in limited sequestration of carbon dioxide by this process of rapid erosion. In many cases where sulfuric acid is a key weathering agent, a net release of CO2 to the atmosphere occurs. This suggests that a causal link between erosion in mountain belts and climate change through the sequestration of CO2, if it exists, must operate through a process other than chemical weathering driven by landsliding. Plain Language Summary There is a long-standing debate surrounding the link between erosion and climate. It is often suggested that as temperatures increase, rainier and stormier weather could increase erosion of rock; as that rock is exposed, silicate minerals within could break down, which, on long time scales, can remove CO2 from the atmosphere, lowering global temperatures and acting as a negative feedback. Recent studies have shown that landslide deposits are key locations for the link between chemical weathering and physical erosion in some mountain belts. To test how landslides affect the erosion-climate link, we used samples of water seeping through landslides in Taiwan and New Zealand to calculate the amount of carbon dioxide that is either absorbed or released through this chemical reaction. We find that the large amount of freshly exposed rock in Taiwanese landslide deposits contains significant carbonate rock and sulfide minerals; the net result of the weathering of these minerals is a release of carbon dioxide, which inverts the traditional perspective on the role erosion plays in controlling carbon dioxide release. In some mountain belts, it seems that increased erosion and resulting landsliding may act to increase carbon dioxide in the air, opening further questions into the nature of erosional-climatic links. KW - chemical weathering KW - landslides KW - erosion-climate link KW - carbon dioxide Y1 - 2018 U6 - https://doi.org/10.1029/2018JF004672 SN - 2169-9003 SN - 2169-9011 VL - 123 IS - 10 SP - 2695 EP - 2713 PB - American Geophysical Union CY - Washington ER -