CRATER CANDIDATE FOR SPHERULE BEARING LAYERS IN THE GULF OF CARPENTARIA AND ARAFURA SEA

For many years, we studied individual spherules and spherule bearing rocks in deep sea sediments from the Gulf of Carpentaria and the Arafura Sea[1]. The magnetic spherules from the Gulf of Carpentaria have quench textures, a modal size of ~ 85 µm and concentrate between 3 and 9 cm subbottom depth. Based on the age and depth of the transition from lacustrine to open ocean conditions in the five MD cores [2], the spherule bearing layers date to the 6^th or 7^th century. In cores MD28, MD29 and MD31, spherule associated rocks contain native Fe, consistent with an impact source for the rocks [3]. Previous crater candidates are not present in recent estimates of bathymetry from satellite altimetry [4]. We examined gravity gradient maps [5] and found a crater candidate in the Arafura Sea that might represent the source of the spherules. Although it could represent a large buried seamount, most large seamounts are part of chains. There is no local seamount chain. The crater candidate in the Arafura Sea is ~30 km in diameter. Based on models of widening of underwater craters by water transport of ejecta [6], the transient crater is predicted to have been ~25 km in diameter. This sizing of the crater candidate is consistent with the observed modal size of the spherules [7].

[1] Abbott, D.H., Martos, S.N., Elkinton, H., Fleming, R., Garcia, A., Chivas, A.R., Breger, D., Haslett, S. and Kaplan, M.R., 2009. AGU FM, 2009, pp.P43B-1436.

[2] Chivas, A.R., Garcı́a, A., van Der Kaars, S., Couapel, M.J., Holt, S., Reeves, J.M., Wheeler, D.J., Switzer, A.D., Murray-Wallace, C.V., Banerjee, D. and Price, D.M., 2001. Quaternary International, 83, pp.19-46.

[3] Bunch, T.E., Hermes, R.E., Moore, A.M., Kennett, D.J., Weaver, J.C., Wittke, J.H., DeCarli, P.S., Bischoff, J.L., Hillman, G.C., Howard, G.A. and Kimbel, D.R., 2012. Proceedings of the National Academy of Sciences, 109(28), pp.E1903-E1912.

[4] Tozer, B., Sandwell, D.T., Smith, W.H.F., Olson, C., Beale, J.R. and Wessel, P., 2019. Earth and Space Science, 6(10), pp.1847-1864.

[5] Sandwell, D.T., Müller, R.D., Smith, W.H., Garcia, E. and Francis, R., 2014. . Science, 346(6205), pp.65-67.

[6] Ormö, J. and Lindström, M., 2000. Geological Magazine, 137(1), pp.67-80.

[7] Johnson, B.C. and Melosh, H.J., 2012. Icarus, 217(1), pp.416-430.