Integrated geophysical characterization of crustal domains in the eastern Black Sea

Abstract

Rifting may lead ultimately to continental breakup, but the identification and characterization of the resulting crustal distribution remains challenging. Also, spatial and temporal changes in breakup magmatism may affect the geophysical character of the newly formed oceanic crust, resulting in contrasting interpretations of crustal composition and distribution. In the Eastern Black Sea Basin (EBSB), the evolution from rifting to breakup has been long debated, with several interpretations for the distribution of stretched continental and oceanic crust. We interpret basement morphological variations from long-offset seismic reflection profiles, highlighting a northwest-to-southeast transition from faulted and tilted continental blocks to a rough and then smoother basement. We model magnetic anomalies to further constrain the various basement domains, and infer the presence of a weakly magnetized, stretched continental crust in the northwest, and a 0.4–3.8 A/m layer coinciding with the smooth basement in the central and southeastern area. We conclude that the EBSB oceanic crust extends farther to the northwest than was suggested previously from an abrupt change in crustal thickness and lower-crustal velocity. The apparent discrepancy between these different types of geophysical evidence may result from changes in magma supply during breakup, affecting the thickness and velocity structure of the resulting oceanic crust.

New Insights Into the Rift‐To‐Drift Process of the Northern South China Sea Margin Constrained by a Three‐Dimensional Wide‐Angle Seismic Velocity Model

“…Locally constrained changes in melt production would also influence the lithospheric thermal structure and the crustal and upper mantle rheology so that the opening in the NE segment was controlled by a balance between tectonic and magmatic additions, whereas opening in the SW segment is comparatively dominated by extensional tectonism. This previously unreported relative small-scale segmentation requires a lithospheric scale transfer fault system (e.g., Koopmann et al, 2014;Monteleone et al, 2020;Shillington et al, 2009) that separates two different opening styles and two melt generation systems indicated by the distinct HVLC distribution (Figure 10).…”

Transmogrification of ocean into continent: implications for continental evolution

“…The second stage is seen in the Black Sea. Here, the seafloor reaches ∼2,000-m depths, with ∼130 My-old Paleotethyan ocean crust and lithosphere now overlain by ∼9 to 12 km of continental sediments ( 8 , 9 ) surrounded by orogenic belts containing both arc and continental crust. The third stage, again involving Paleotethyan oceanic crust, is seen in the South Caspian Sea.…”