Reply to the Discussion of He et al. (2011, Geo-Marine Letters) Evidence of internal-wave and internal-tide deposits in the Middle Ordovician Xujiajuan Formation of the Xiangshan Group, Ningxia, China

Abstract

A point-by-point reply is here made to the discussion put forward by G. Shanmugam of our recent paper on internal-wave and internal-tide deposits in the Middle Ordovician Xujiajuan Formation of the Xiangshan Group, Ningxia, China. We readily acknowledge that some issues raised by that author are pertinent. However, others are inconsequential, marginal, disputable, or redundant. The available evidence clearly supports our interpretation that the Middle Ordovician Xujiajuan Formation was deposited in a deep-water setting. Furthermore, we uphold that an internal-wave and internal-tide interpretation for these deposits is plausible in view of the occurrence of bidirectional cross-bedding and unidirectional cross-bedding dipping upslope in a deep-water environment. Also, we consider the request to provide conclusive evidence for the existence of a pycnocline in our stratigraphic record as unreasonable—it is self-evident that these data are currently not available, and the absence of proof is not proof of the contrary.