DOI: 10.1016/j.palaeo.2020.109652
论文题名: Re-investigating Miocene age control and paleoenvironmental reconstructions in western Amazonia (northwestern Solimões Basin, Brazil)
作者: Kern A.K. ; Gross M. ; Galeazzi C.P. ; Pupim F.N. ; Sawakuchi A.O. ; Almeida R.P. ; Piller W.E. ; Kuhlmann G.G. ; Basei M.A.S.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 310182
出版年: 2020
卷: 545 语种: 英语
英文关键词: Amazon rainforest
; Biostratigraphy
; Detrital zircon ages
; Neogene
; Ostracods
; Palynology
Scopus关键词: age determination
; biostratigraphy
; detrital deposit
; landscape change
; Miocene
; Neogene
; ostracod
; paleoenvironment
; palynology
; rainforest
; reconstruction
; Amazonas [Brazil]
; Brazil
; Solimoes Basin
; Cyprideis
; Ostracoda
英文摘要: The modern Amazonian rainforest has a great fascination and global significance, but our knowledge of past landscape changes is still limited due to sparse data and the lack of radiometric age constrains. Precise dating in records older than the late Pleistocene are difficult to obtain and often regionally confined, therefore biostratigraphic correlations are used to estimate depositional ages across sedimentary basins. Aiming for a better understanding of the Neogene changes in western Brazil, we studied palynology and ostracod assemblages from the Solimões Formation, a key site for paleoenvironmental models to discuss the biotic changes in Amazonia. Further, we compare the biostratigraphic information of both groups with radiometric maximum deposition ages constrained by U/Pb measurements on detrital zircon grains. Down to the depth of ~95 m, zircon populations show a maximum deposition age of 11.42 ± 0.66 Ma documenting Tortonian (late Miocene) or younger ages for the top of the Solimões Formation. Palynological biostratigraphy show the Psilatricolporites caribbiensis zone (latest Miocene–Pliocene) down to a depth of 181.8 m, where the Grimsdalea magnaclavata zone suggests a late middle Miocene to early late Miocene age. In comparison, ostracod biostratigraphy indicates the Cyprideis cyrtoma zone (late Miocene) down to 176.0 m and the Cyprideis minipunctata (late middle to late Miocene) for the bottom of the section. Thus, both biostratigraphic concepts suggest ages close to the maximum ages indicated by the detrital zircons. This comparison of the biozonations with U/Pb maximum deposition ages represents the first independent calibration of these widely used methods for age determination in the Solimões Basin. Palynological and ostracod data illustrate dynamic environments varying from fluvial settings with wetland forests and swamps to lakes and/or abandoned channels with temporary slightly saline conditions. Instead of a slow evolution of Neogene Amazonian environments, our results show migrating rivers and waterbodies surrounded by rainforest during the period recorded by the base and top of the studied core material, separated by a phase of more extensive lakes and swamps (core depth 90–120 m). Indicators for slightly elevated salinity are found until the topmost sample and thus persisted during the late Miocene. This highlights the importance of new age control to improve the regional biostratigraphic timescale and reconstructed environmental changes. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/158302
Appears in Collections: 气候变化与战略
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作者单位: Instituto de Geociências, Universidade de São Paulo, São Paulo, SP, Brazil; Department for Geology and Palaeontology, Universalmuseum Joanneum, Graz, Austria; Departamento de Ciências Ambientais, Universidade Federal de São Paulo, Diadema, SP, Brazil; Institute of Earth Science, NAWI Graz Geocenter, University of Graz, Graz, Austria
Recommended Citation:
Kern A.K.,Gross M.,Galeazzi C.P.,et al. Re-investigating Miocene age control and paleoenvironmental reconstructions in western Amazonia (northwestern Solimões Basin, Brazil)[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2020-01-01,545