CONTROLLING FACTORS AND EVOLUTION PROCESS OF FLOOD-TIDAL DELTAS/DEPOSITS IN SEMI-CLOSED MID-TIDE COASTAL LAGOONS: INSIGHTS FROM THE CHAOYANGGANG PORT, SHANDONG PENINSULA, CHINA

Flood-tidal deltas are defined as wedge-shaped accumulations of sediments on the landward side of an inlet and could make great petroleum reservoirs. However, controlled by the amphibious environment of marine and terrestrial deposits, the influencing factors are complex. Predecessors have difficulties in studying the dynamic evolution process of the flood-tidal deltas in the barrier island-lagoon sedimentary system. The sedimentary characteristics of each flood-tidal delta lobe are rarely compared, and further research is needed on the controlling factors affecting the development of flood-tidal deltas.

This research took the widely developed flood-tidal deltas in the coastal lagoon of Chaoyanggang Port as an example. It is a wonderful natural laboratory for studying the flood-tidal deltas/sediments in the lagoon on the semi-enclosed mid-tidal coast.

We study the depositional units, evolution characteristics and controlling factors of the flood-tidal deltas by analyzing the characteristics of lithology, grain size, sedimentary structure, hydrodynamics, and geomorphology. Based on the above analyses, the forward modeling of the flood-tidal deltas‘ evolution in the study area was carried out by Delft 3D.

The results show that the barrier island-lagoon sedimentary system contained four sedimentary facies, among which the flood-tidal deltas contained five subfacies. The flood-tidal deltas are distributed along both sides of the main tidal channel, and their development scale, lithology, thickness, grain size and sedimentary structural characteristics show regular changes in the direction of the flood tide. The factors affecting the development of flood-tidal deltas mainly include dynamic factors, topographic factors and human activities. The forward modeling of Delft 3D based on the above influencing factors reproduces the sedimentary evolution of lobes well.

Through the research on the modern sedimentation of flood-tidal deltas in a barrier island-lagoon sedimentary system, we hope to deepen the recognition of their depositional mechanism, evolutionary process and provide theoretical guidance on the formation of flood-tidal deltas and their reservoir characteristics in the paleo-sedimentary period.