Neogene Sedimentary Environment and Provenance Evolution Recorded by Core ZKA5 in the Yangtze River Delta

[Objective] The Cenozoic provenance evolution of the northern Yangtze River Delta remains poorly understood due to a scarcity of continuous, deep sedimentary records. [Methods] To address this knowledge gap, we present a comprehensive analysis of the upper 408 m unconsolidated succession from Core ZKA5, located in the Nantong area. Through integrated lithological observation, grain size analysis, and detailed heavy mineral identification, we reconstruct the sedimentary environmental history and delineate the provenance shifts since the late Cenozoic. [Results] Our results show that the stratigraphic sequence comprises six lithostratigraphic units, include the Yancheng, Haimen, Qidong, Kunshan, Gehu, and Rudong Formations, and is characterized by five sedimentary facies, include alluvial plain, channel, floodplain, delta plain, and intertidal facies. Heavy mineral assemblages reveal a significant provenance transition. Sediments during the late Neogene were predominantly sourced from the northern basin of the middle-upper Huai River. However, beginning in the early Quaternary (approximately at ~2.6 Ma), the dominant sediment source has progressively shifted from the Huai River basin to the middle‑lower reaches of the Yangtze River basin. [Conclusion] We interpret this provenance shift to be primarily driven by the southward migration of the regional depocenter from the Subei Basin to the Yangtze River Delta, coupled with changes in the East Asian monsoon precipitation regime during the Quaternary. [Significance] This study reveals the transformation of the provenance system driven by tectonic subsidence and climatic forcing, providing critical empirical evidence for the tectono-sedimentary-modification coupling mechanism in the Yangtze River Delta.