A combined paleomagnetic/dating investigation of the upper Jaramillo transition from a volcanic section at Tenerife (Canary Islands)

Abstract

A coupled paleomagnetic/dating investigation has been conducted on a sequence of 25 successive lava flows, emplaced during the upper transition of the Jaramillo subchron in Tenerife, Canary Islands. This sequence is located along the western wall of the Güímar collapse scar, in the south central part of the island. Nine flows distributed throughout this sequence were dated using unspiked K/Ar and 40Ar/39Ar methods. They bracket the section between 1009±22 ka and 971±21 ka (2σ). A first group of 8 flows at the bottom of the sequence is characterized by normal polarity with paleointensity values of the order of present-day field intensity in the Canary Islands. The virtual geomagnetic poles (VGP) of these 8 flows describe a short loop at high latitudes. Seven overlying flows are transitional in directions and dated between 991±14 ka and 1002±11 ka consistently with published ages of the upper Jaramillo reversal. This second group of flows is characterized by low paleointensity values (around 8-12 μT) that are less than 30% of the present dipole value in Tenerife. The VGPs of the first two transitional flows lie over northeastern Pacific whereas the five following transitional flows have all negative inclinations and their VGPs lie initially over East Antarctica, then describe a northward loop almost reaching New Zealand. The final group of ten flows yield intensities varying between 20 and 35 μT and VGPs close to the southern pole with two of them describing a small amplitude second loop to southeastern Pacific. Assuming a constant extrusion rate as a very first approximation, the distribution of the obtained ages suggests a duration of 7.6±5.6 ka for the transitional interval. The obtained transitional positions of VGPs are consistent with the path reported for the same reversal from North Atlantic sediments but are different from the only other volcanic record from Tahiti. The intensity low characterizing the transitional interval remains the best tie point, centered at 996±7 ka (2σ) relative to 28.02 Ma FC sanidine.