{"id":5823,"date":"2023-06-15T14:56:38","date_gmt":"2023-06-15T12:56:38","guid":{"rendered":"https:\/\/sites.uclouvain.be\/geo-team-vv\/?p=5823"},"modified":"2023-06-15T14:56:40","modified_gmt":"2023-06-15T12:56:40","slug":"what-controls-erosion-dynamics-in-madagascar","status":"publish","type":"post","link":"https:\/\/sites.uclouvain.be\/geo-team-vv\/2023\/06\/15\/what-controls-erosion-dynamics-in-madagascar\/","title":{"rendered":"What controls erosion dynamics in Madagascar?"},"content":{"rendered":"\n

Madagascar is a microcontinent with locally steep topography and active seismicity despite being surrounded by passive margins. Cosmogenic nuclide analysis of river sediment provides insight into catchment-wide erosion rates and dynamics. In this paper, we investigated spatial patterns and controls on 10<\/sup>Be-inferred erosion rates in Madagascar, a moderately seismically active microcontinent surrounded by passive margins with locally steep topography and a climate that varies from humid tropical to semiarid. <\/p>\n\n\n

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We use a compiled dataset of 99 detrital 10<\/sup>Be measurements, 63 of which are new, covering more than 30% of the country and a wide range of topographic, bioclimatic and geologic characteristics. Overall, 10<\/sup>Be erosion rates are low (2.4\u201351.1\u2009mm kyr\u22121<\/sup>), with clear differences between regions. The lowest rates are measured on the central highlands ( 8\u2009mm kyr\u22121<\/sup>), in the Alaotra\u2013Ankay graben ( 11\u2009mm kyr\u22121<\/sup>) and in the large north-central catchments ( 11\u2009mm kyr\u22121<\/sup>). Higher rates are found on the steep eastern escarpment ( 20\u2009mm kyr\u22121<\/sup>), in the northwest ( 31\u2009mm kyr\u22121<\/sup>) and in the southwest ( 29\u2009mm kyr\u22121<\/sup>).<\/p>\n\n\n\n

\"Denudation<\/figure>\n\n\n\n

Figure shows the 10<\/sup>Be erosion rates organised from north to south for the different regions. Marker size represents the catchment area. Boxplots are included for regions that contain sufficient sampled catchments. Hollow dots represent outliers (id = 30, 32, 37, indicated by grey boxplot dots) and catchments in the east that encompass more than one region (id = 94, 95) and are not included in statistical analysis. <\/em><\/p>\n\n\n\n

Higher 10<\/sup>Be erosion rates were associated with lower river concavity (more convex shaped rivers) and higher seismic activity both at the level of individual catchments as well as at the regional level, while higher lavaka densities explain regional variations. No relationship between 10<\/sup>Be erosion rates and slope gradient or river steepness was observed, which brings into question the general applicability of fluvial metrics to constrain vertical incision rates in a slowly eroding landscape such as Madagascar.<\/p>\n\n\n\n

While 10<\/sup>Be concentrations suggest that rates of landscape change in Madagascar are low, there are indications that chemical weathering rates may outpace CRN-derived denudation rates, pointing to the importance of deep weathering and removal of dissolved materials. In thick regolith-mantled landscapes, mass losses by deep weathering and sub-surface dissolution should be considered alongside with mass losses by physical erosion.<\/p>\n\n\n\n

More information : Brosens, L., Cox, R., Campforts, B., Jacobs, L., Vanacker, V., Bierman, P. et al. (2023) The slow downwearing of Madagascar: Inferring patterns and controls on long-term basin-averaged erosion rates from in situ<\/em> 10<\/sup>Be at the catchment and regional level.<\/a> Earth Surface Processes and Landforms<\/em>, 1\u2013 18. Available from: https:\/\/doi.org\/10.1002\/esp.5586<\/a><\/p>\n\n\n\n

References<\/strong><\/p>\n\n\n\n

Cox, R., Bierman, P., Jungers, M.C., Rakotondrazafy, A. F. M. (2009) Erosion rates and sediment sources in Madagascar inferred from 10<\/sup>Be analysis of lavaka, slope, and river sediment. The Journal of Geology<\/em>, 117(4), 363\u2013 376. Available from: http:\/\/www.journals.uchicago.edu\/doi\/10.1086\/598945<\/a><\/p>\n\n\n\n

Wang, Y., Willett, S.D., Wu, D., Haghipour, N. & Christl, M. (2021) Retreat of the great escarpment of Madagascar from geomorphic analysis and cosmogenic 10<\/sup>Be concentrations. Geochemistry, Geophysics, Geosystems<\/em>, 22(12), e2021GC009979. Available from: https:\/\/onlinelibrary.wiley.com\/doi\/10.1029\/2021GC009979<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Madagascar is a microcontinent with locally steep topography and active seismicity despite being surrounded by passive margins. Cosmogenic nuclide analysis of river sediment provides insight into catchment-wide erosion rates and dynamics. In this paper, we investigated spatial patterns and controls on 10Be-inferred erosion rates in Madagascar, a moderately seismically active microcontinent surrounded by passive margins… Read More »What controls erosion dynamics in Madagascar?<\/span><\/a><\/p>\n","protected":false},"author":33,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"","neve_meta_content_width":0,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","_themeisle_gutenberg_block_has_review":false,"footnotes":""},"categories":[23],"tags":[53,63],"class_list":["post-5823","post","type-post","status-publish","format-standard","hentry","category-publication","tag-denudation-rate","tag-madagascar"],"_links":{"self":[{"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/posts\/5823","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/users\/33"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/comments?post=5823"}],"version-history":[{"count":6,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/posts\/5823\/revisions"}],"predecessor-version":[{"id":6203,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/posts\/5823\/revisions\/6203"}],"wp:attachment":[{"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/media?parent=5823"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/categories?post=5823"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/sites.uclouvain.be\/geo-team-vv\/wp-json\/wp\/v2\/tags?post=5823"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}