Chronology of late pliocene and early pleistocene glacial and magnetic events in southern Argentina

Precise ages of the Réunion event and Huckleberry Ridge excursion: Episodic clustering of geomagnetic instabilities and the dynamics of flow within the outer core

“…7). Four concordant plateaus ranging in age from 2.084 ± 0.005/0.006 to 2.097 ± 0.004/0.006 Ma were generated from what we interpret to be antecrysts, thereby confirming the observations of Rivera et al (2014) and Gansecki et al (1998), but at a scale that the latter study could not resolve owing to large single-crystal uncertainties. is in excess of the single data point uncertainties which range from 10.4 to 96.6 kyr (2σ ) (Fig.…”

“…Numerous K-Ar and 40 Ar/ 39 Ar ages between 2.0 and 2.1 Ma have been obtained from HRT members A, B, and C (Gansecki et al, 1998;Lanphere et al, 2002, and references within). Gansecki et al (1998) measured 21 sanidine grains from sample 2R577 collected near the middle of member B, which is the most voluminous of the three members. The weighted mean 40 Ar/ 39 Ar age (n = 9), wherein we have excluded a 2.25 Ma xenocryst and analyses that have <90% radiogenic 40 Ar * or K/Ca <10, is 2.059 ± 0.031 Ma (Fig.…”

“…The Huckleberry Ridge Tuff (HRT), the oldest and largest ash-flow tuff of the Yellowstone Plateau volcanic field, has long been associated with the Réunion event based on a common transitional paleomagnetic direction determined from tuff members A, B, and C (Reynolds, 1977). Numerous K-Ar and 40 Ar/ 39 Ar ages between 2.0 and 2.1 Ma have been obtained from HRT members A, B, and C (Gansecki et al, 1998;Lanphere et al, 2002, and references within). Gansecki et al (1998) measured 21 sanidine grains from sample 2R577 collected near the middle of member B, which is the most voluminous of the three members.…”

“…Everts) of Lanphere et al (2002) are the plateau ages from an incremental heating experiments on 15-52 mg of sanidine. Data of Gansecki et al (1998) has been filtered to remove xenocrysts, analyses with <90% 40 Ar * , and grains that were not completely fused (see text for details). The 40 Ar/ 39 Ar and U-Pb ages from Rivera et al (2014) for the Huckleberry Ridge tuff are mean values of the youngest modes of populations of single crystal sanidine and zircon dates.…”

Ice-Rafted Debris in Sediments from Leg 71, Southwest Atlantic Ocean

“…Several tills in Patagonia have been dated at 2.10 to 1.71 Ma, the thickest being between 2.10 and 1.91 m.y. old (Fleck et al, 1972, andMercer (1976) has determined that the most severe glacial phase in Patagonia occurred 1.3 to 1.0 Ma.…”