气候变化领域集成服务门户(CCPortal): Palaeosalinity and palaeoclimatic geochemical proxies (elements Ti; Mg; Al) vary with Milankovitch cyclicity (1.3 to 2.0 Ma); OGCP cores; Palaeolake Olduvai; Tanzania

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DOI	10.1016/j.palaeo.2020.109656
	Palaeosalinity and palaeoclimatic geochemical proxies (elements Ti; Mg; Al) vary with Milankovitch cyclicity (1.3 to 2.0 Ma); OGCP cores; Palaeolake Olduvai; Tanzania
	Stanistreet I.G.; Boyle J.F.; Stollhofen H.; Deocampo D.M.; Deino A.; McHenry L.J.; Toth N.; Schick K.; Njau J.K.
发表日期	2020
ISSN	0031-0182
卷号	546
英文摘要	The analysis of geochemical palaeoclimate and palaeosalinity proxy elements Ti, Mg, and Al, derived from X-ray fluorescence (XRF) scans of Olduvai Beds I and II from Olduvai Gorge Coring Project (OGCP) borehole Cores 2A and 3A, provides a record of cyclic variation between ~1.3 Ma and ~2.0 Ma. The boreholes were drilled into the depocentre of the Olduvai Basin between Fifth and FLK Faults, where Palaeolake Olduvai was most persistent and deepest. During most of Bed I the lake was particularly deep and probably meromictic, preserving high TOC contents and commonly preserving fine lamination due to lack of bioturbation. Accretion rates were also high during Bed I, when rates of basinal subsidence were maximal due to crustal stretching, associated with basaltic volcanism, towards the end of bimodal Ngorongoro volcanism. Basaltic magma effusive activity is manifested as tuffs, scoriaceous layers and the Bed I Basalt complex lava flows. A magnesium anomaly is recorded in the claystone geochemistry at this time and deposition of dolomite and limestone beds are restricted to this syn-volcanic phase of basin history. During Bed I deposition, accretion rates (0.23 mm/yr) were high enough to permit recognition of cycles with an average periodicity of 22.3 kyr corresponding to the Earth's precession. Only the high values during the Mg anomaly are adequate for the application of the palaeosalinity proxy element ratio Mg/Al. But Ti counts provide a cyclic record in both Bed I and Bed II. During Bed II deposition, the accretion rate was much slower (0.058 mm/yr) and cyclicity averaged 40.4 kyr, corresponding to Earth's orbital obliquity. The Bed II interval corresponds to MIS Stages 40 to 64. Coincidence of precessional and obliquity minima at 1.8 Ma explains the superdrought that affected the basin at the time of emplacement of Tuff IF, when the lake was dried out. The aridity of the sequence containing Tuff IA is also associated with a precessional minimum. The cyclic record suggests that three Bed I Basalt flows were extruded at ~1.94 Ma during a time span lasting between 6 kyr and 15 kyr. © 2020
英文关键词	Basaltic magmatism; Obliquity; Olduvai Basin; Orbital forcing; Precession; XRF scanning
语种	英语
scopus关键词	anomaly; aridity; borehole; claystone; cyclicity; dolomite; limestone; magmatism; paleoclimate; Arusha [Tanzania]; Ngorongoro; Olduvai Gorge; Tanzania
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/150536
作者单位	Dept. Earth, Ocean and Ecological Sciences, University of Liverpool, Brownlow Street, Liverpool, L69 3GP, United Kingdom; The Stone Age Institute, Bloomington, IN 47407-5097, United States; Dept. Geography and Planning, School of Environmental Sciences, University of Liverpool, Liverpool, United Kingdom; GeoZentrum Nordbayern, Friedrich-Alexander-University (FAU) Erlangen-Nürnberg, Schloßgarten 5, Erlangen, 91054, Germany; Dept. Geosciences, Georgia State University, Atlanta, GA, United States; Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, United States; Department of Geosciences, University of Wisconsin-Milwaukee, 3209 N. Maryland Ave., Milwaukee, WI 53211, United States; Department of Earth and Atmospheric Sciences, Indiana University, 1001 East 10th Street, Bloomington, IN 47405-1405, United States
推荐引用方式 GB/T 7714	Stanistreet I.G.,Boyle J.F.,Stollhofen H.,et al. Palaeosalinity and palaeoclimatic geochemical proxies (elements Ti; Mg; Al) vary with Milankovitch cyclicity (1.3 to 2.0 Ma); OGCP cores; Palaeolake Olduvai; Tanzania[J],2020,546.
APA	Stanistreet I.G..,Boyle J.F..,Stollhofen H..,Deocampo D.M..,Deino A..,...&Njau J.K..(2020).Palaeosalinity and palaeoclimatic geochemical proxies (elements Ti; Mg; Al) vary with Milankovitch cyclicity (1.3 to 2.0 Ma); OGCP cores; Palaeolake Olduvai; Tanzania.Palaeogeography, Palaeoclimatology, Palaeoecology,546.
MLA	Stanistreet I.G.,et al."Palaeosalinity and palaeoclimatic geochemical proxies (elements Ti; Mg; Al) vary with Milankovitch cyclicity (1.3 to 2.0 Ma); OGCP cores; Palaeolake Olduvai; Tanzania".Palaeogeography, Palaeoclimatology, Palaeoecology 546(2020).