Astronomical calibration of the Matuyama-Brunhes boundary; consequences for magnetic remanence acquisition in marine carbonates and the Asian loess sequences

Author(s): Tauxe, L.; Herbert, T.; Shackleton, N. J.; Kok, Y. S.
Author Affiliation(s): Primary:
Fort Hoofddijk Paleomagnetic Laboratory, Utrecht, Netherlands
Other:
Scripps Institution of Oceanography, La Jolla, CA 92093-0220, United States
Godwin Institute for Quaternary Research, The Godwin Laboratory, Free School Lane, Cambridge, United Kingdom
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 140(1-4), p.133-146. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 69 refs.; illus., incl. 2 tables, sketch map
Summary: We have compiled 19 records from marine carbonate cores in which the Matuyama-Brunhes boundary (MBB) has been reasonably well constrained within the astronomically forced stratigraphic framework using oxygen isotopes. By correlation of the δ18O data to a timescale based on astronomical forcing, we estimate astronomical ages for each of the MBB horizons. In all but one record the MBB occurs within Stage 19. Most magnetostratigraphic sections in Asian Loess place the MBB within a loess interval. Since loess deposition is presumed to be associated with glacial intervals, loess horizons should correspond to even-numbered oxygen isotope stages. A glacial age for the MBB is at odds with the results presented here, which firmly place the MBB within interglacial Stage 19. Inconsistency among the many loess sections and between the loess and the marine records suggests that the magnetic interpretation of loess sections may be more complicated than hitherto supposed. The mean of the Stage 19 age estimates for the MBB is 777.9±1.8 (N=18). Inclusion of the single Stage 20 age results in a mean of 778.8±2.5 (N=19). The astronomical age estimate of the MBB compares favorably with an (unweighted) mean of 778.2±3.5 (N=10) from a compilation of 40Ar/39Ar results of transitional lava flows. Combining the two independent data sets yields a grand mean of 778.0±1.7 (N=28). The new compilation shows virtually no trend in placement of the MBB within isotope Stage 19 as a function of sediment accumulation rate. We interpret this to mean that the average depth of remanence acquisition is within a few centimeters of the sediment-water interface. Separating the cores into two geographic regions (an Indo-Pacific-Caribbean [IPC] Group and an Atlantic Group) results in a significant difference in the position of the mid-point of the reversal with respect to the astronomical time scale. The data presented here suggest a difference of several thousand years between the two regions. This observation could be caused by systematic differences between the two regions in sedimentation rate within the interval of interest, systematic differences in remanence acquisition, or by genuine differences in the timing of the directional changes between the two regions. Abstract Copyright (1996) Elsevier, B.V.
Year of Publication: 1996
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 03 Geochronology; 07 Marine Geology and Oceanography; 24 Surficial Geology, Quaternary Geology; Absolute age; Ar/Ar; Asia; Atlantic Ocean; Brunhes Chron; Calibration; Carbonate sediments; Caribbean Sea; Cenozoic; Clastic sediments; Cores; Dates; Geochronology; Igneous rocks; Indian Ocean; Isotope ratios; Isotopes; Loess; Magnetization; Magnetostratigraphy; Marine sediments; Matuyama Chron; Milankovitch theory; North Atlantic; O-18/O-16; Oxygen; Pacific Ocean; Paleomagnetism; Quaternary; Remanent magnetization; Reversals; Sediments; Stable isotopes; Stratigraphic boundary; Time scales; Upper Cenozoic; Upper Quaternary; Volcanic rocks
Record ID: 1996047184
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

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