Australasian microtektites in the South China Sea and the West Philippine Sea: Implications for age, size, and location of the impact crater

Abstract

Abstract-Microtektites from two deep-sea cores in the South China Sea and the West Philippine Sea are identified as belonging to the Australasian tektite strewn field based on the morphology, chronostratigraphic occurrence, and geographical location of these microtektites. The higher concentrations of microtektites (> 1000/cm2) in the marginal seas of the western Pacific, with the peak concentration in the South China Sea, support the hypothesis of a large impact crater in Indochina. These two new occurrences lead to a more precise dating of the impact event at 793 ka, whereas the size of the Australasian source crater on the Indochina Peninsula is estimated to be 90-1 16 km.

Toward establishing a maritime proxy record of the East Asian summer monsoons for the late Quaternary

“…Numbers mark the marine isotope stages correlated to the low-latitude stack of Bassinot et al (1994). Shown on the top are the magnetostratigraphy from Lee (2000), the last occurrence datum of pink G. ruber, and the position of the Australasian microtektite layer (marked as mtk) (Lee and Wei, 2000).…”

“…The scale for the MD972142 N 18 O is shown on the left axis while that for the low-latitude stack is on the right axis. Shown on the top are the magnetic polarity from Lee (2000), the last occurrence datum of pink G. ruber, and the interval of Australasian microtektites (marked as mtk) (Lee and Wei, 2000). The ¢nal ¢xpoints for the timescale are listed in Table 1. of terrestrial freshwater runo¡ and exchange e⁄-cacy with open-ocean saline waters) should have contributed to amplifying the N 18 O variation.…”

“…The widespread Australasian microtektites caused by an asteroid impact on the Indochina Peninsula slightly before the Matuyama/Brunhes geomagnetic boundary serves as an independent age marker to line up the three records under scrutiny: the microtektites (symbolized as mTK in Fig. 5) were found within the oxygen isotope stage 20 in Core MD972142 (Lee and Wei, 2000) and ODP769 (Schnieder et al, 1992;Kent and Schneider, 1995), and within the loess unit L8 at the Louchuan section (Fig. 5) (Li et al, 1993, ¢de Zhou andShackleton, 1999).…”

“…The Brunhes/ Matuyama geomagnetic reversal at 33.70 m (Lee, 2000) assists in positioning the marine isotopic stages 19 and 20. The occurrence of Australasian microtektites at the subdepths 33.85^34.45 m further constrains the age of this interval to be V770^790 ka (Izett and Obradovich, 1992;Tauxe et al, 1996;Lee and Wei, 2000). These biostratigraphic, magnetostratigraphic and microtektite markers were used as independent controls in assisting the correlation of the resulted pro¢le with the low-latitude stack (Bassinot et al, 1994) (Fig.…”

Giant comets and mass extinctions of life

“…Two non-crater impact structures were added: (a) Simms (2003Simms ( , 2007 has identified a seismite layer which appears to have been created from another large impact, yielding perhaps a 40-50 km unidentified crater, at least 600 km west or northwest of central Britain; and (b) the Australasian tektites have been added; their source crater too has not been identified, but published estimates of its size range from 30 to 120 km (Lee & Wei 2000). Thus the database comprises 41 well-dated impact structures covering the last 500 Myr.…”