NUMERICAL ESTIMATION AND MODELING OF SHELF PROCESSES: EXAMPLES FROM THE NIGER DELTA, GULF OF MEXICO, GULF OF PAPUA AND WAIPAOA RIVER BASINS

Abstract

This study presents the first quantitative analysis of the Miocene deposits in the Niger Delta, revealing a tide-dominated system with tidal facies making up 53%, fluvial facies 33%, and wave-formed facies 14%. Core analyses from wells located in the Greater Ughelli, Central, and Coastal Swamp depobelts of the Niger Delta indicate prograding deltaic facies with significant tidal influence, marked by seasonal deposition and flood events. These findings reflect delta-plain and delta-front to prodeltaic environments, shaped by complex interactions between tidal, wave, and river forces. In addition, this work evaluates the ichnofacies model of siliciclastic marine environments using cores from the modern Mississippi Delta (USA), Gulf of Papua (New Guinea), and Waipaoa River Basin (New Zealand). Six facies, ranging from laminated sands to bioturbated muds, were identified, reflecting storm, wave and river processes. Traces like Helminthopsis and Chondrites align with ancient deposits’ ichnological models, particularly the recently defined Phycosiphon Ichnofacies, which characterizes muddy prodelta settings. This confirms that traces found in modern depositional environments correspond to those found in ancient systems, offering valuable insights for interpreting ancient shelf deposits. The study also examines the modern Brazos Delta, Texas (USA) focusing on sedimentation rates and biogenic activities that influence facies distribution and event bed preservation. Analysis of 26 core samples reveals five distinct facies, indicating sedimentary processes influenced by inputs from the Brazos River and the Gulf of Mexico shelf. The sediment composition, predominantly clay (40%) and silt (50%), shows distinct facies patterns along the river mouth and in the downdrift/updrift areas. Variations in sediment accumulation rates, driven by fluvial flood events and marine processes, highlight the delta's sensitivity to local climate dynamics. These studies show that quantitative analysis and ichnological data are vital for interpreting depositional environments, bridging modeling gaps, and understanding sediment distribution in both ancient and modern settings.