The discovery and significance of a sedimentary hiatus within the Carboniferous Taiyuan Formation, northeastern Ordos Basin, China: Reply

Abstract

We thank Zheng et al. (2016) for their comments on our previous work of sedimentary hiatus within the Carboniferous Taiyuan Formation, northeastern Ordos Basin, China (Jiang et al., 2012). Zheng et al. (2016) have different opinions on sedimentary facies and sequence stratigraphy interpretation in the study area. They question our interpretation based on their understanding of sedimentary facies, seismic geometry, orientation of sand body, and sand body thickness. Here, we provide additional evidence to reinforce our interpretation. The structure of this reply follows the order of the questions raised by Zheng et al. (2016). The interpretation of depositional environment for sand bodies in the Upper Pennsylvanian Taiyuan Formation (Ct2) has been controversial for decades. Some previous studies suggested that Ct2 represents a barrier–lagoon–tidal flat system (e.g., Hao et al., 2007; Wang et al., 2007). Zheng et al. (2016) also made such an interpretation. However, northeast–southwest-trending sand bodies in Ct2 were interpreted as fluvial–deltaic channels by many other studies (e.g., Li et al., 1995; Liu, 1998; Fu et al., 2003; Guo et al., 2009; Zhang et al., 2009; Luo et al., 2011). The braided stream fills of the incised valley were documented by extensive erosional surfaces, conglomerate and/or mud clast fluvial lag deposits, and trough cross bedding. Erosional surfaces are one of the most common features observed in cores of Ct2 interval (Figure 1; see also figure 4 in Jiang et al., 2012). The poorly sorted gravels are aligned in various directions, indicating a rapid deposit without significant tidal reworking (Figure 1E). In contrast, the sedimentary structures that Zheng et al. (2016) interpreted as tidal–barrier island signatures, such as mud drapes and cross bedding, can be also found in fluvial deposits. Figure 1. Sedimentary features of fluvial deposit in the …