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SUMMARY:Hot blobs\, swells and sea level - Bryan Lovell (University of Cam
 bridge)
DTSTART:20090121T163000Z
DTEND:20090121T173000Z
UID:TALK15169@talks.cam.ac.uk
CONTACT:Dr Alistair Crosby
DESCRIPTION:Vail et al. (1977) recognized that there was no plausible mech
 anism in non-glacial times for their proposed higher frequency (“third-o
 rder”) cycles of sea-level.  An explanation for these one to ten million
  year events has been elusive: at least this part of the Vail eustatic mod
 el remains unproven.  A review of research on mantle processes over the pa
 st three decades shows that mantle-induced vertical motions of Earth’s s
 urface can occur over time intervals from several tens of millions of year
 s down to less than one million years\, and can have amplitudes of hundred
 s of metres\, even at the shorter intervals. These vertical motions can oc
 cur worldwide and are not merely associated with major hotspots.  Mantle c
 onvection therefore provides a mechanism for explaining some second- and t
 hird-order sea-level cycles. The planform pattern of the convection exerts
  a first-order control on stratigraphy by creating swells or depressions w
 ith typical diameters of one to two thousand kilometres\, and durations of
  uplift or subsidence from a few million years to tens of millions of year
 s. Vertical motions that result from episodic pulsing of mantle plumes are
  characterized by rapid rates over intervals of several million years down
  to less than one million years. These effects are evident in the sediment
 ary record of North Atlantic basins\, with peak uplift seen at Middle Jura
 ssic\, Early Cretaceous\, Eocene and Neogene.  Caution is therefore requir
 ed before interpreting rapid (less than one million years) and high amplit
 ude (tens of metres) sea-level fluctuations as eustatic in origin.\n
LOCATION:Marine/Wolfson Building lecture hall
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