K-Ar ages of the Quaternary basalts in the Jeongok area, the central part of Korean Peninsula

Abstract

The Quaternary basalts along the Chugaryeong Fault zone in central part of the Korean Peninsula are composed of two stratigraphic units in the Jeongok area, calling the Chatan and Jeongok basalts. K-Ar analyses of the mixture of the finegrained plagioclase and anorthoclase from the 18 basalt samples were carried out to reveal the volcanic activity of the area. The results show that the Chatan and Jeongok basalts give a uniform age, giving the weighted average ages of 0.15 ± 0.01 and 0.51 ± 0.01 Ma, respectively. This reveals the age gap between the Chatan and Jeongok basalts was 360,000 years, providing a unique volcanic history for the Quaternary volcanism. The volcanism formed the two large amounts of alkali olivine basalt flows that are similar to each other in primitive chemical composition, phenocryst composition and viscosity with an interval of 360,000 years. The results also make a time constraint on the Jeongok Paleolithic Site where the Jeongok basalt occurs below the sediments containing the Paleolithic artifacts. The age (0.51 Ma) of the Jeongok basalt provides the lower limit for the age of Paleolithic artifacts. Olivine phenocrysts from both the Chatan and Jeongok basalts have significant amount of excess argon, giving apparent older ages on the whole rock K-Ar dating by previous researchers.

Improvement of 40Ar/39Ar age determinations for Quaternary basaltic rocks by eliminating the peak suppression effect

“…9 with the previous K-Ar age data. The revised protocol successfully reproduces 40 Ar/ 39 Ar age results similar to the average K-Ar ages of 150 ± 10 Ka and 510 ± 10 Ka from Ryu et al (2011). In addition, other volcanic activity at ca.…”

“…In addition, the mantle source component of the Jeongok basalt is different from that of other Cenozoic basalt in Korea (Choi et al 2006). Ryu et al (2011) suggested that there were two major volcanic eruptions in this area, at ca. 150 and 510 Ka based on K-Ar ages.…”

Probabilistic Analysis of the Korean Historical Earthquake Records

“…However, the tectonic evolution responsible for formation of the Chugaryeong fault system remains unclear (e.g., Shibuya et al, 1985;Ryu et al, 2011). The crust of the Korean Peninsula presents typical characteristics of a continental crust.…”

Feedback of Slab Distortion on Volcanic Arc Evolution: Geochemical Perspective From Late Cenozoic Volcanism in SW Japan

“…The NHRL in Figures 6d and 6e is Northern Hemisphere Reference Line (Hart, 1984). Sources for literature data: Quaternary ADK (adakitic high‐Sr andesites and dacites) in the Chugoku district (Feineman et al, 2013; Kimura, Gill, et al, 2014; Kimura et al, 2015; Pineda‐Velasco et al, 2015, 2018), Cenozoic basalts in East Asia (Basu et al, 1991; Brenna et al, 2014; Brenna, Cronin, Smith, Maas, et al, 2012; Brenna, Cronin, Smith, Sohn, et al, 2012; Chen et al, 2007, 2018; Choi et al, 2006, 2008, 2014; Choi & Kim, 2012; Choi & Kwon, 2005; Ho et al, 2003; Kuritani et al, 2009, 2011, 2013, 2017; Liu et al, 1994; Park et al, 2005; Ryu et al, 2011; Sakuyama et al, 2013; Sakuyama, Nagaoka, et al, 2014; Sakuyama, Nakai, et al, 2014; Song et al, 1990; Sun et al, 2014; Tatsumi et al, 2005; Tatsumoto & Nakamura, 1991; Wang et al, 2011; Xu et al, 2013; Zeng et al, 2013; Zhang et al, 1995, 2012, 2015; Zou, 1998; Zou et al, 2000, 2003), seafloor basalts from Pacific and Shikoku Basin (Pineda‐Velasco et al, 2018, references therein), sediments (Ben Othman et al, 1989; Chauvel et al, 2009; Cousens et al, 1994; Hauff et al, 2003; Hemming & McLennan, 2001; Ishikawa & Nakamura, 1994; Pearce et al, 1999; Plank et al, 2007; Shimoda et al, 1998; Terakado et al, 1988). ...…”