Tesis de Licenciatura. Magnetoestratigrafía de los sedimentos lacustres Plioceos de la sección de Galera (Cuenca de Gaudix-Baza, Cordilleras Béticas)

Miquel Garcés Crespo


Magnetostratigraphy of the Upper Pliocene lacustrine sediments
from the Galera section (Guadix-Baza Basin, Betic Ranges, Spain) The late Pliocene shallow lacustrine sequences in the Guadix-Baza basin (Betic Ranges, SE Spain) are a privileged setting for mammal chronology because of the abundance of rich mammal-bearing sites. Stratigraphic superposition of late Ruscinian and Villanyian vertebrate fossils makes the Galera Section very appropriate for magnetostrati-graphic dating. Sediments are characterized by a weak but measurable magnetization predominantly carried by magnetite. Other remanence carriers as iron sulfides and hematite may be significant only in some particular lithologies, such as dark palustrine organic silts and interlayered red alluvial beds respectively. Direct correlation of the Galera Section to the geomagnetic polarity time scale has lead to a reliable dating of the Late Ruscinian and Villanyian mammal units. The RuscinianíVillanyian boundary (MN15íMN16) is found to occur in the middle part of chron C2An, between 2.7 Ma and 3.3 Ma, and possibly correlates to the 3.2 Ma cooling event observed in stable-isotope and planktonic foraminiferal deep sea records. Earliest ocurrence of late Villanyian assemblages (MN17) in the lower part of the Matuyama chron allows to date the earlyllate Villanyian boundary (MN16lMN17) to approximatelly 2.4-2.6 Ma. Based on the presence of late Villanyian assemblages underlying the base of the Olduvai chron, a maximum age
of 1.95 Ma (top of C2r) is attributed to the VillanyianIBiharian (MN171MmQ) boundary. A 300 kyr sedimentary gap in the Galera section is suggested to correlate with a probable early Villanyian basin-wide hiatus, hipothesis that agrees with the absence of fossil remains of this age elsewhere in the Baza Fm.


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