Basin Research最新文献

Shelf-edge evolution in tectonically active basins reflects complex interactions between structural deformation, sea-level change and sedimentary processes. This study investigates Middle Miocene clinoform successions (14.00–12.50 Ma) in the southwestern Ulleung Basin, East Sea, using 3D seismic data to examine how erosional processes modulate structurally-controlled shelf-edge migration patterns. Eight clinothems were identified, showing cyclic alternations between sigmoidal types (ascending trajectories) and thin-top sigmoidal/oblique types (flat-to-descending trajectories), possibly reflecting high-frequency relative sea-level cycles (4th–5th order). A reverse fault system in the southeast of the study area (DS A) formed monocline structure that created differential accommodation along the shelf margin. The structure caused reduced accommodation space favouring oblique clinothems in the uplifted proximal area and maintained more space resulting in thin-top sigmoidal clinothems distally. Conventional tectono-stratigraphic models often predict that such uplift enhances shelf-edge progradation, producing arcuate shelf-edge geometry in map view. However, shelf-edge migration remained relatively linear without enhanced shelf-edge migration toward the reverse fault system, contradicting these established models. The interaction between the structural deformation and erosional processes on the shelf margins explains these shelf-edge behaviours. The structural deformation (DS A) that controlled clinoform type variation also induced slope oversteepening that promoted erosional features at shelf margins within 20 km of this structure. These erosional depressions formed atop sigmoidal clinothems during early stage of sea-level fall, creating additional accommodation at the shelf margin that moderated shelf-edge advance. This ‘erosional modulation’ process represents a compensatory mechanism where uplift-induced oversteepening creates preferential erosion sites that generate offsetting accommodation, preventing the expected translation of structural deformation into margin architecture. The recurrence of this process across multiple stratigraphic cycles suggests that erosional modulation operates as a persistent architectural control rather than independent random events. These findings provide new insights into how erosional processes can modulate shelf-edge evolution, particularly in tectonically active settings, complementing traditional models that assume direct translation of structural deformation into margin architecture.

Extensive deposition of thick marine evaporites occurred during the middle and late Miocene in the Gulf of Suez rift basin, yet their origin remains controversial, particularly regarding marine connectivity, brine sources, and climatic controls. In the St. Paul area, at the western rift margin, stacked, shallowing-upward cycles of shale, mudstone, and evaporite grade landward into conglomerate and sandstone of proximal fan facies. A detailed sedimentological and sequence stratigraphic study offers new insights into the evolution of these Langhian–Serravallian marginal marine evaporites and their basinal equivalents, clarifying the timing of restriction events and proposing viable models for their accumulation. The evaporites, mainly epigenetic anhydrite, occur as nodular forms with chicken-wire and enterolithic textures, indicative of deposition in saline mudflats under a hot, arid climate. This marine-fed, siliciclastic-rich sabkha flat lacks a modern analog due to its uncommon mud matrix. Periodic continental flooding disrupted the sabkha mudflat, leading to the deposition of laminated and fanned gypsum in ephemeral saline pans. The stratal architecture of the evaporites and associated sediments reveals three depositional sequences, each with a lower retrograding deep subtidal shale and basal channelled sandstone, and an upper prograding shallow subtidal to intertidal siliciclastic mud and supratidal evaporites. Sabkha and salina evaporites mark the late highstand facies, while lowstand evaporites formed in the basin centre when it became isolated and hypersaline due to evaporative drawdown. Three major marine flooding events from the Mediterranean had occurred during the Langhian–Serravallian, prior to complete basin isolation from the north. Each event culminated in extensive evaporite accumulation as the basin became temporarily isolated. Rift-related tectonics, global cooling, glacio-eustasy, and changes in basin connectivity were key drivers of temporary restrictions, while arid climate controlled brine concentration. These findings resolve some long-standing debates on the origin of the Gulf of Suez evaporites and their connection to the northern Mediterranean source during the Miocene.