The multidisciplinary study of the 60-m-deep continental SC1 core from the Sulmona lacustrine succession (central Italy) allowed to retrieve high-resolution paleomagnetic and climatic data for the Early-Middle Pleistocene time interval. The SC1 core encompasses the Brunhes-Matuyama boundary and the Ar/Ar dating of the several tephra layers therein contained provides a firm chronology for the whole sedimentary succession. The sediment accumulation rates are in the order of 0.2 mm/yr. The MIS20-MIS19 interval, where the B-M polarity reversal occurs, has been studied in detail by means of climatic proxies on discrete samples (oxygen isotopes, CaCO3 content, magnetic susceptibility) and paleomagnetic analyses on u-channels. Data have been also gathered and reproduced from the outcrops of the Sulmona lacustrine succession (the Horseshoe section), thus strengthening the results obtained from the core. Paleomagnetic analyses points to the occurrence of two main intensity minima, of which the younger pertains to the generally recognized B-M polarity reversal and the older is interpreted as its precursor. The precursor occurs few thousands years before the B-M polarity transition during the Termination IX, between MIS20 and MIS19. The intensity minimum of the B-M transition falls in the early part of MIS19, with a stable configuration of the magnetic inclinations already reached soon after the end of the Termination IX. Comparison with the available records, where paleomagnetic and climatic data are coupled, reveals that the climatostratigraphic position of the precursor is quite well established, falling in the Termination IX. Conversely the position of the B-M transition wiggles inside the MIS19. The discrepancy in the positioning of the two magnetic events may find explanation in the quality of magnetic signal recording in the different sedimentary environments. Taking into account that the precursor is commonly well positioned because it occurs on a well detectable climatic termination, we suggest that some bias may have occurred in the tuning of the climatic records for the MIS19-MIS18 transition thus leading to a wrong positioning of the B-M boundary in some sedimentary records.
Climatostratigraphic position of the Brunhes-Matuyama transition and its precursor
G Scardia;B Giaccio;P Messina
2013
Abstract
The multidisciplinary study of the 60-m-deep continental SC1 core from the Sulmona lacustrine succession (central Italy) allowed to retrieve high-resolution paleomagnetic and climatic data for the Early-Middle Pleistocene time interval. The SC1 core encompasses the Brunhes-Matuyama boundary and the Ar/Ar dating of the several tephra layers therein contained provides a firm chronology for the whole sedimentary succession. The sediment accumulation rates are in the order of 0.2 mm/yr. The MIS20-MIS19 interval, where the B-M polarity reversal occurs, has been studied in detail by means of climatic proxies on discrete samples (oxygen isotopes, CaCO3 content, magnetic susceptibility) and paleomagnetic analyses on u-channels. Data have been also gathered and reproduced from the outcrops of the Sulmona lacustrine succession (the Horseshoe section), thus strengthening the results obtained from the core. Paleomagnetic analyses points to the occurrence of two main intensity minima, of which the younger pertains to the generally recognized B-M polarity reversal and the older is interpreted as its precursor. The precursor occurs few thousands years before the B-M polarity transition during the Termination IX, between MIS20 and MIS19. The intensity minimum of the B-M transition falls in the early part of MIS19, with a stable configuration of the magnetic inclinations already reached soon after the end of the Termination IX. Comparison with the available records, where paleomagnetic and climatic data are coupled, reveals that the climatostratigraphic position of the precursor is quite well established, falling in the Termination IX. Conversely the position of the B-M transition wiggles inside the MIS19. The discrepancy in the positioning of the two magnetic events may find explanation in the quality of magnetic signal recording in the different sedimentary environments. Taking into account that the precursor is commonly well positioned because it occurs on a well detectable climatic termination, we suggest that some bias may have occurred in the tuning of the climatic records for the MIS19-MIS18 transition thus leading to a wrong positioning of the B-M boundary in some sedimentary records.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
