Multi-method absolute paleointensity determinations on a Pliocene
multiple-polarity record from the Lesser Caucasus
Abstract
We report high technical quality absolute paleointensity determinations
from a Pliocene sequence of 20 consecutive lava flows sampled in South
Georgia named Apnia, which record either the Gilbert-Gauss polarity
reversal or a composite transition from chron C2Ar to subchron C2An-2n.
Paleointensity determinations with the multispecimen (MSP) technique
were performed on 12 samples with both the original method (MSP-DB) and
the extended protocol with corrections (MSP-DSC). Six MSP-DB and eight
MSP-DSC determinations passed the proposed quality criteria. MSP-DB
yielded higher intensity values than MSP-DSC. In order to provide
additional reliability to the results, we have carried out a consistency
test by means of a multi-method approach. We have compared the MSP
intensities with Thellier-type intensities obtained from the
reinterpretation of determinations performed in previous study. The
match of both types of paleointensity determinations gives the results
an added reliability. Paleointensity results have been obtained in all
20 flows, 11 of which were supported on different methods. At the
reverse polarity lower section, low-VADM values between 2.1 and 4.2 x 10
Am were obtained. The single transitional flow displayed 4.3 x 10 Am,
and the normal polarity upper section showed higher values between 5.1
and 7.1 x 10 Am. The lower section results might be a pre-reversal stage
record and the upper section may reflect the intensity recovery after
the complete reversal. Furthermore, the results comparison from both
methods will allow the evaluation of the quality parameters proposed to
MSP method, which are controversial given the novelty of the technique.