The Ground Penetrating Radar facies and architecture of a Paleo-spit from Huangqihai Lake, North China: Implications for genesis and evolution

A paleo-spit is identified from Huangqihai Lake in North China and proposed as a classic example for investigating the influence of lake level changes and storms on the construction of these bodies. Ground Penetrating Radar (GPR) data, collected with a 400 MHz antenna, are used together with sedimentologic observations from trenches to define the facies and sedimentary architecture of the spit. Six types of radar surface, both depositional and erosional, were identified. Radar facies bounded by radar surfaces were interpreted from reflection characteristics and termination patterns. Eight different radar facies were identified in the profiles, and we assign these to three groups (inclined, horizontal and irregular). The whole barrier spit system comprises spit bar and salt marsh units, distinguished using GPR profiles. Linked radar and sedimentologic data are used to develop a model for spit bar evolution. The spit was formed during a cycle of lake-level change spanning ~ 200 years. The characteristics of the different building blocks (washover lobes, sheets and swash laminated sands) within the spit bar unit and their depositional regimes are defined and interpreted. Based on the known lake evolution during the Holocene, a relative chronological framework is presented. Two storms in the 1880s and 1960s may have played an important role in building the spit bar.