Astronomical calibration of Oligocene--Miocene time

• DOI: 10.1098/rsta.1999.0407
• Publication Date: 2002-07-26T19:55:21Z
• Authors: N. J. Shackleton; S. J. Crowhurst; G. P. Weedon; J. Laskar
• Keywords: Precession; Eccentricity (behavior); Orbital forcing; Chronology

Lithological cyclicity was observed aboard the JOIDES RESOLUTION in sediment sequences recovered from Ceara Rise during ODP Leg 154. Shipboard work led to conclusion that Oligocene probably characterized by ca. 41 ka cycles. Weedon and others were able confirm this, created a provisional time–scale for assuming is response orbital obliquity variation, using spectral analysis estimate mean wavelength hence sedimentation rate of successive intervals core. We have extended this intercorrelating almost all 9.5 m cores each four sites sediment. successfully correlated material covering time–interval 10 Ma 18 28 Ma, as well most 14 34 intervals. Although variability dominated cycle there sufficient at precession period (amplitude–modulated eccentricity) permit an absolute placement section with reference calculated history. Further needed establish precisely implications calibration geological but it appears true ages events close Oligocene–Miocene boundary are 0.9 younger than they appear on recently published time–scales. The sedimentary record preserves information concerning amplitude modulation signal astronomical significance.