DOI: 10.1016/j.chemgeo.2020.119473
论文题名: Re-Os geochronology and isotope systematics, and organic and sulfur geochemistry of the middle–late Paleocene Waipawa Formation, New Zealand: Insights into early Paleogene seawater Os isotope composition
作者: Rotich E.K. ; Handler M.R. ; Naeher S. ; Selby D. ; Hollis C.J. ; Sykes R.
刊名: Chemical Geology
ISSN: 92541
出版年: 2020
卷: 536 语种: 英语
英文关键词: New Zealand
; Paleocene
; Re-Os geochronology
; Seawater Os curve
; Waipawa Formation
Scopus关键词: Binary alloys
; Binding sites
; Biogeochemistry
; Chelation
; Geochronology
; Isotopes
; Organic compounds
; Rhenium alloys
; Seawater
; Sedimentology
; Submarine geology
; Sulfur
; Sulfur compounds
; Weathering
; Geological history
; Global temperatures
; New zealand
; Oceanographic conditions
; Oil and gas production
; Paleocene
; Sedimentation rates
; Waipawa Formation
; Sedimentary rocks
; geochronology
; isotopic composition
; lithostratigraphy
; organic geochemistry
; osmium isotope
; Paleocene
; rhenium-osmium dating
; seawater
; sulfur
; New Zealand
; Pacific Ocean
; Pacific Ocean (Southwest)
英文摘要: In the middle–late Paleocene, a marine, organic-rich sedimentary unit (Waipawa Formation [Fm]) in which the organic matter was derived mainly from terrestrial plants was deposited in many of New Zealand's sedimentary basins. The unique organofacies of this formation has not been identified in any other time interval within the geological history of the Southwest Pacific, indicating that unusual climatic and oceanographic conditions likely prevailed during this time. It has, therefore, attracted wide scientific interest due to its significance for regional and global reconstruction of the early Paleogene transitional climate as well as potential for oil and gas production. Scarcity of age-diagnostic fossils, presence of unconformities and lack of volcanic interbeds have, however, hindered precise dating and correlations of all the known occurrences of the formation. Here, rhenium‑osmium (Re-Os) geochronology has yielded the first radiometric age for the formation (57.5 ± 3.5 Ma), which is consistent with available biostratigraphic age determinations (59.4–58.7 Ma). Further, a comparison of Re-Os, bulk pyrolysis, sulfur and palynofacies data for the Waipawa Fm with those of more typical marine sediments such as the underlying Whangai Fm supports the interpretation that the chelating precursors or fundamental binding sites responsible for uptake of Re and Os are present in all types of organic matter, and that these elements have a greater affinity for organic chelating sites than for sulfides. The results also indicate that sedimentation rate may not play a dominant role in enhanced uptake of Re and Os by organic-rich sedimentary rocks. The initial 187Os/188Os values for the Waipawa (~0.28) and Whangai (~0.36) formations are broadly similar to those reported for coeval pelagic sediments from the central Pacific Ocean, further constraining the low-resolution marine 187Os/188Os record of the Paleocene. We present a compilation of 187Os/188Os values from organic-rich sedimentary rocks spanning the period between 70 and 50 Ma which shows that seawater Os gradually became less radiogenic from the latest Cretaceous, reaching a minimum value in the earliest late Paleocene (~59 Ma) during the deposition of Waipawa Fm, and then increased through the later Paleocene and into the early Eocene. The composite Os isotope record broadly correlates with global temperature (δ18O and TEX86) and carbon isotope (δ13C) records from the middle Paleocene to early Eocene, which is inferred to reflect climate-modulated changes in continental weathering patterns. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/158653
Appears in Collections: 气候变化与战略
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作者单位: School of Geography, Environment and Earth Sciences, Victoria University of Wellington, PO Box 600, Wellington, 6140, New Zealand; GNS Science, 1 Fairway Drive, PO Box 30368, Lower Hutt, 5040, New Zealand; Department of Earth Sciences, Durham University, Durham, DH1 3LE, United Kingdom; State Key Laboratory of Geological Processes and Mineral Resources, School of Earth Resources, China University of Geosciences, Wuhan, Hubei 430074, China
Recommended Citation:
Rotich E.K.,Handler M.R.,Naeher S.,et al. Re-Os geochronology and isotope systematics, and organic and sulfur geochemistry of the middle–late Paleocene Waipawa Formation, New Zealand: Insights into early Paleogene seawater Os isotope composition[J]. Chemical Geology,2020-01-01,536