Aspects of the structure of the Porcupine and Porcupine Seabight basins as revealed from gravity modelling of regional seismic transects

Abstract

AbstractThe Porcupine Basin is characterized by a large central free air gravity anomaly high (+ 55 mGal) flanked by local lows. In contrast, the Procupine Seabight Basin has low-amplitude anomalies in its centre, flanked by edge anomalies. Two transects, one in each of these basins, have been modelled using satellite gravity data; the upper parts of the transects are constrained by interpretation of recent commercial seismic reflection data and two wells. Results from the modelling suggest that the Porcupine Basin is not in isostatic equilibrium. In contrast, the essentially zero free air anomaly over the centre of the Porcupine Seabight Basin suggests that this basin is isostatically compensated. The difference in isostatic compensation between the two basins may reflect a fundamental contrast between the strength of the crust; the crust underlying the Porcupine Basin possesses the greater strength. The Clare Lineament may represent a fundamental boundary within the ‘Avalonian Terrane’ that juxtaposes basement blocks of differing rheologies.