Higher-order eccentricity cycles of the middle and late Miocene climatic variations

Tiwari, R. K.

doi:10.1038/327219a0

Cited by 27 publications

(6 citation statements)

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“…The duration of each zone (ca. 400 kyr) coincides with the earth's eccentricity cycle inferred also in Miocene sediments with similar sources and settings (Abrajevitch et al, 2009;Tiwari, 1987), but the short duration of the present subsection and lack of supporting data on climate proxies prevent us from further verification of this inference.…”

Section: Interpretation and Discussionsupporting

confidence: 65%

Magneto‐chemical signature of the Lower‐to‐Middle Siwaliks transition in the Karnali River section (Western Nepal): Implications for Himalayan tectonics and climate

et al. 2019

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Fluviatile sediments comprising a 600-m-thick sequence of the Lower and Middle Siwaliks in the Karnali area in Nepal exhibit a distinct zonation revealed by magnetic and geochemical properties. Four magneto-chemical zones (MCZ1-MCZ4), each about 150 m thick and 400 kyr in duration, provide new insights on Himalayan tectonoclimatic events during the Tortonian (Miocene) stage. They exhibit contrasting magnetic susceptibility and isothermal remanence due to differences in magnetic mineral types (magnetite, hematite, and goethite) and concentrations. Odd-numbered zones with higher goethite/(goethite + hematite) ratio, a moisture proxy, indicate wetter conditions in the source area, while the even-numbered zones, virtually without goethite, suggest drier conditions. Chemical indices of alteration/weathering and proxies for hydraulic sorting and mobility derived from the major element compositions also reveal contrasts among these zones. The middle of the MCZ2-MCZ3 zone, with a transitional magneto-chemical signature, is the best candidate for the Lower to Middle Siwaliks contact, rather than the field-based boundary placed 18 m up-section at the base of the thick salt and pepper sandstone bed. The transition records an increase in river energy and associated accelerated erosion of the Himalayan gneiss zone as the source of coarse-grained material. We suggest a scenario, whereby climate change from drier to wetter (with higher precipitation) conditions affects erosional processes (i.e., weathering, disaggregation and particle transport on the hillslope) prevailing in a large catchment and influencing the depositional modes.

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Section: Interpretation and Discussionsupporting

confidence: 65%

Magneto‐chemical signature of the Lower‐to‐Middle Siwaliks transition in the Karnali River section (Western Nepal): Implications for Himalayan tectonics and climate

et al. 2019

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“…4), in g k d accordance with the results from the sedimentary para-Sedimentary event Occurrences have long been noticed to be rhythmic, with the prospect of estimating the durations of the geological stages if it can be shown that the climate responds to the astronomical forcing (Berger, 1977;Schwarzacher, 1954;1975;Fischer, 1964;1980). This has been demonstrated unequivocally for Pleistocene sediments (Emiliani, 1966;Hays et al, 1976;Rooth et al, 1978) up to 2 Myr old (Chave and Denham, 1979) and of Miocene age (Tiwari, 1987). But while the relationship between orbital parameters, climate and sedimentary record has been extensively studied (Berger et al, 1984), the correlation between the climate changes and the magnetic record in the sediments remains poorly explored.…”

Section: Rhythms Andsupporting

confidence: 63%

Cyclic geomagnetic changes in Mid‐Cretaceous rhythmites, Italy

Napoleone

Ripepe

1989

Terra Nova

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Magnetic secular variation is recorded as a quasi-rhythmical process of uncertain origin. Rhythmic changes recorded in the Scisti a Fucoidi in the central Apennines of Italy, pelagic sediments of Mid-Cretaceous (Late Albian) age, show strong correspondence to patterns of orbital variation. In the same strata cyclic magnetic variations are found with peaks in the same range (105,40,26,19 kyr). These results appear to support earlier suggestions that secular variations may be related to these astronomical patterns.

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“…There is some evi dence that a 400-k.y. cycle may occur (e.g., during the Miocene [Moore et al 1982;Tiwari 1987] and the Quaternary [Briskin and Harrell 1980]). Berger (1984) and Berger and Pestiaux (1984) cautioned that while it is now possible to calculate values for eccentricity, preces sion, and tilt back to 5 Ma, unknown aspects of celestial mechanics could become signifi cant on longer time scales.…”

Section: Milankovitch Cyclesmentioning

confidence: 99%

Milankovitch cycles and their effects on species in ecological and evolutionary time

1990

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The Quaternary ice ages were paced by astronomical cycles with periodicities of 20–100 k.y. (Milankovitch cycles). These cycles have been present throughout earth history. The Quaternary fossil record, marine and terrestrial, near to and remote from centers of glaciation, shows that communities of plants and animals are temporary, lasting only a few thousand years at the most. Response of populations to the climatic changes of Quaternary Milankovitch cycles can be taken as typical of the way populations have behaved throughout earth history. Milankovitch cycles thus force an instability of climate and other aspects of the biotic and abiotic environment on time scales much less than typical species durations (1–30 m.y.). Any microevolutionary change that accumulates on a time scale of thousands of years is likely to be lost as communities are reorganized following climatic changes. A four-tier hierarchy of time scales for evolutionary processes can be constructed as follows: ecological time (thousands of years), Milankovitch cycles (20–100 k.y.), geological time (millions of years), mass extinctions (approximately 26 m.y.). “Ecological time” and “geological time” are defined temporally as the intervals between events of the second and fourth tiers, respectively. Gould's (1985) “paradox of the first tier” can be resolved, at least in part, through the undoing of Darwinian natural selection at the first tier by Milankovitch cycles at the second tier.

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Higher-order eccentricity cycles of the middle and late Miocene climatic variations

Cited by 27 publications

References 0 publications

Magneto‐chemical signature of the Lower‐to‐Middle Siwaliks transition in the Karnali River section (Western Nepal): Implications for Himalayan tectonics and climate

Magneto‐chemical signature of the Lower‐to‐Middle Siwaliks transition in the Karnali River section (Western Nepal): Implications for Himalayan tectonics and climate

Cyclic geomagnetic changes in Mid‐Cretaceous rhythmites, Italy

Milankovitch cycles and their effects on species in ecological and evolutionary time

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