Cosmic ray effects and faunal extinctions at geomagnetic field reversals

Black, Daniella

doi:10.1016/0012-821x(67)90042-8

Cited by 34 publications

(26 citation statements)

References 34 publications

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“…The search is based on the belief that a geomagnetic reversal is accompanied by the lowering of the dipole intensity to a near-zero level. During this zero-field period, which has been variously estimated to last for about 1000 yr. (Kawai et al, 1975) to 5000 yr. (Harrison and Somayajulu, 1966;Cox et al, 1975), cosmogenic isotope production would be increased two-or threefold (Black, 1967;O'Brian, 1979). If so, a change in 10 Be concentration might be found in sediments deposited during that period.…”

Section: Be Input Variation Near Geomagnetic Reversalmentioning

confidence: 99%

10Be Distributions in Deep Sea Drilling Project Site 576 and Site 578 Sediments Studied by Accelerator Mass Spectrometry

Ku¹,

Southon²,

Vogel³

et al. 1985

Initial Reports of the Deep Sea Drilling Project

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Extension of the 10 Be geochronology for deep-sea sediments beyond the limit of late Pliocene age found in published works has been attempted. The results obtained on sediments from Deep Sea Drilling Project (DSDP) Sites 576 and 578 of Leg 86 suggest the feasibility of dating sediments as old as 12 to 15 m.y. At both sites, there have been large changes in sedimentation rate, with the Pleistocene sediments accumulating several times faster than those of the Pliocene, which in turn were deposited several times more rapidly than the late Miocene sediments. The Pleistocene-Pliocene section is considerably thicker in Hole 578 than in Hole 576B: the respective depths for the 7-m.y. time boundary in the two holes are ~ 125 and ~25 m. These 10 Be-based age estimates are in agreement with the paleomagnetic stratigraphies established for the two sites. The suggested enhancement in the oceanic deposition of 10 Be before 7 to 9 m.y. ago, as noticed in manganese crusts, has found tentative support from the present sedimentary records. A preliminary search for 10 Be production variation during a geomagnetic field reversal has been conducted. In Hole 578, an enhanced 10 Be concentration is found in a sample close to the Brunhes/Matuyama reversal boundary. More detailed and systematic measurements are required to confirm this observation, which bears on the detailed behavior of the geomagnetic field during the reversal.

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Section: Be Input Variation Near Geomagnetic Reversalmentioning

confidence: 99%

10Be Distributions in Deep Sea Drilling Project Site 576 and Site 578 Sediments Studied by Accelerator Mass Spectrometry

Ku¹,

Southon²,

Vogel³

et al. 1985

Initial Reports of the Deep Sea Drilling Project

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“…His discussion on possible radiation effects on the biosphere is rather detailed, concluding that these effects cannot explain any relation between geomagnetic field variations and faunal boundaries. Thus Black (1967) reasons that, if the observed simultaneity of a faunal boundary and a reversal was not chance, some external event enforced this correlation. Thus a new question arises from his study: What cosmic event could have triggered both, polarity transitions and mass extinctions?…”

Section: Early Conjectures On the Geomagnetic Linkmentioning

confidence: 87%

“…The figure is courtesy Frank Wissmann, PTB Braunschweig particular, he critically discussed studies of deep-sea cores indicating a relation between the last polarity reversal and the extinction of a group of radiolarian species by Harrison and Funnell (1964), Opdyke et al (1966), and Watkins and Goodell (1967). He concludes that only one confirmed correlation between a polarity change and faunal boundary exists (Black 1967). His discussion on possible radiation effects on the biosphere is rather detailed, concluding that these effects cannot explain any relation between geomagnetic field variations and faunal boundaries.…”

Section: Early Conjectures On the Geomagnetic Linkmentioning

confidence: 95%

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Magnetic Polarity Transitions and Biospheric Effects

Glaßmeier

Vogt

2010

Space Sci Rev

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This review addresses possible biospheric effects of geomagnetic polarity transitions. During a transition the magnetic field at the surface of the Earth decreases to about 10% of its current value. If the geomagnetic field is a shield against energetic particles of solar or cosmic origin then biospheric effects can be expected. We review the early speculations on the problem and discuss in more detail its current status. We conclude that no clear picture of a geomagnetic link, a causal relation between secular magnetic field variations and the evolution of life on our planet can be drawn.

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“…A mere increase in overall radiation flux was thus deemed to be an insufficient cause for catastrophic events on earth, Earlier attempts to relate end-Cretaceous extinctions to radiation damage (Schindewolf, 1954;, therefore, mainly concentrated on cosmic radiation penetrating the atmosphere for a brief period during geomagnetic reversals (Uffen, 1963;Simpson, 1966;Hatfield and Camp, 1970). It was then shown that the increase in such radiation levels at the earth's surface would be insignificant (Black, 1967;Waddington, 1967;Harrison, 1968). Life has not developed any defense mechanism against the very short wave radiation of less than about 280 rim, suggesting that the thermosphere has always acted as shield against potentially lethal, unchecked penetration of gamma-ray, X-ray and even most of ultraviolet-A (short wave UV) radiation.…”

Section: Increased Solar Radiationmentioning

confidence: 99%

Effects of a variable sun at the beginning of the Cenozoic era

Sonnenfeld

1978

Climatic Change

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Periodic bursts of increased ultraviolet radiation, possibly caused by a long-term breakdown of the ozone layer in late Cretaceous to early Tertiary time, can explain the staggered extinctions of terrestrial, marine and flying reptiles, of invertebrate plankton feeders. Inherited protective devices and habits of surviving genera support this hypothesis. Increased radiation also explains the concurrent decrease in aridity indicated by the world-wide absence of marine salt and potash deposits from Maestrichtian, Danian, Paleocene and Eocene sediments, the poleward displacement of marine tropical faunas and the warm-temperate forests in high latitudes. A magnetic reversal is too brief an event to be responsible for the faunal changes; variations in solar radiation of the order of the Kelvin-Helmholtz time, or 30-40 million years, with superimposed shorter periodicities are a probable cause.

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Cosmic ray effects and faunal extinctions at geomagnetic field reversals

Cited by 34 publications

References 34 publications

10Be Distributions in Deep Sea Drilling Project Site 576 and Site 578 Sediments Studied by Accelerator Mass Spectrometry

10Be Distributions in Deep Sea Drilling Project Site 576 and Site 578 Sediments Studied by Accelerator Mass Spectrometry

Magnetic Polarity Transitions and Biospheric Effects

Effects of a variable sun at the beginning of the Cenozoic era

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