Evidence of a South Asian Proto‐Monsoon During the Oligocene‐Miocene Transition

Abstract

 Geochemical data from eastern Arabian Sea indicate Oligocene-Miocene transition is key interval of strengthening of South Asian proto-monsoon  Early phase of transition (23.7-23.0 Ma) displays intensification of winter monsoonlike circulation associated with global cooling  'Deglaciation' phase (23.0-22.7 Ma) triggers the establishment of OMZ, signalling the strengthening of proto-monsoon atmospheric circulation Accepted ArticleThis article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Phylogenomic study of Amorphophallus (Alismatales; Araceae): When plastid DNA gene sequences help to resolve the backbone subgeneric delineation

“…15–13 Ma) with the establishment of a permanent Antarctic ice‐sheet (Zachos et al, 2008; Liu et al, 2009; Beddow et al, 2016; Hutchinson et al, 2021). These periods coincided with the emergence of seasonal biomes in Europe and Asia, the aridification of Australian, African, and Asian inlands, and the subsequent contraction of the tropics with tropical forests retreating to lower latitudes (Morley, 2003; Bowen, 2007; Contreras et al, 2013; Fang et al, 2015; Lin et al, 2015; Beasley et al, 2021; Couvreur et al, 2021). Moreover, all above geo‐climatic changes, associated with sea level drops, have led to major turnovers of the vegetation (Sun et al, 2015; Pound & Salzmann, 2017; Couvreur et al, 2021), with successful plant dispersal across different paleogeographic regions (Jiang et al, 2019), and the establishment of present‐day genera and families in multiple regions, probably pre‐adapted to current climates (e.g., Linnemann et al, 2017; Su et al, 2018; Huang et al, 2021; Ling et al, 2021).…”

Strontium isotope stratigraphy of marine Oligocene–Miocene sedimentary successions of Kutch Basin, western India

“…On the other hand, the increase in sedimentation during Early Miocene of the Kutch Basin is in agreement with the sediment budgets derived from seismic stratigraphy data from the Indus Fan which shows rapid erosion during the early-late Miocene (24-11 Ma) in response to Himalayan uplift and precipitation changes largely related to monsoon strengthening (Figure 11) (Clift, 2006(Clift, , 2010(Clift, , 2017. Alternatively, a relative increase in the terrigenous fraction coincident with strengthening of a proto-South Asian monsoon system, is also reported at the F I G U R E 1 1 Temporal framework of sedimentation rates in the Oligocene-Miocene sections of the Kutch Basin and their comparison to published data from Arabian Sea (Beasley et al, 2021;Clift, 2006;Nair et al, 2021;Pandey et al, 2020) and Bay of Bengal (Krishna et al, 2016) sites, and to global climatic variability (Mathew et al, 2020;Zachos et al, 2001).…”

“…Oligocene-Miocene transition (Beasley et al, 2021;Clift, 2006). Likewise, sediment accumulation rates estimated from the Laxmi Basin of the eastern Arabian Sea showed maximum sedimentation during early-middle to late Miocene (Nair et al, 2021;Pandey et al, 2020).…”

“…In the Indian subcontinent, the late Oligocene to Miocene interval, marked by changes in climate, sedimentation and weathering, was largely influenced by the northward drift of the Indian Plate and uplift of the Himalaya–Tibetan plateau (Clift, 2006; Clift & Jonell, 2021; Tada & Murray, 2016; Upreti & Srivastava, 2020). The sedimentological and geochemical data of the sediment core (NGHP‐01‐01A) from the eastern Arabian Sea show strengthening of a proto‐summer South Asian monsoon system in the latter part of the Oligocene–Miocene transition (∼23.0 Ma), possibly related to changes in orbital parameters, as well as the evolution of the Himalayan‐Tibetan orogen (Beasley et al, 2021). The Early Miocene (ca.…”

“…Furthermore, a suite of well‐established redox‐sensitive trace element ratios (V/Ni, Ni/Co, and V/Cr) was also used to infer the redox‐status of Oligo–Miocene sedimentary formations during their deposition (Bennett & Canfield, 2020; Tribovillard et al, 2006). There is a limited amount of information currently available on how the palaeo‐redox conditions responded to the tectonic and palaeoclimatic changes during the Oligocene–Miocene in the Indian subcontinent (Beasley et al, 2021; Singh & Gupta, 2004). Specifically, the objectives of this study are to (i) establish the strontium isotope ( 87 Sr/ 86 Sr) numerical ages of marine Oligocene and Miocene sections of Kutch Basin, western India and (ii) assess the palaeo‐redox conditions during deposition of the sedimentary successions using trace element ratios, particularly V/Ni, V/Cr and Ni/Co.…”