The Orera section (Calatayud Basin, NE Spain) - Universiteit Utrecht

especially related to obliquity and eccentricity, an astronomical tuning for the Cascante cycles is
not presented.
Finally, in Chapter 6 the necessity to distinguish tiny wiggles in terms ofreversal excursions or
short polarity subchrons is outlined. Because of their unclear nature and origin, tiny wiggles are
also referred to as cryptochrons in the GPTS of CK92. Hence, an unambiguous distinction
between reversal excursions and short polarity events (subchrons) is not easily made. In this
chapter, it is discussed whether a distinction can be made on the basis of duration and nature of
the polarity reversal. Therefore, paleomagnetic, rock magnetic and geochemical results of
detailed sample sets from three short normal polarity intervals in the OCS magnetostratigraphy,
are presented. The results indicate that the polarity signals of these intervals are true features of
the geomagnetic field with magnetite and fine-grained hematite as the main magnetic minerals.
Using the ages ofthe astronomically calibrated OCS and determining the latitudinal variation of
the virtual geomagnetic poles (VGP paths), the duration and the origin of the short polarity
events is determined. Based on these results, the presence of a new subchron CSf.2r-1n, earlier
identified as cryptochron CSf.Zr-1 in ODP Leg 138, is confirmed. The duration and nature of
the VGP paths of the two other short polarity events do not allow a straightforward distinction
between a (short) subchron and reversal excursion. Hence, the two events are recognised as new
cryptochrons CSf.zr-z and Csr.3r-1, however, their existence requires confirmation in other
records.
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