Crustal Structure of Laurentia and Peri‐Gondwanan Terranes Beneath Ireland and Britain and Comparison With Eastern North America

Abstract The Appalachian‐Caledonian orogen was built during the Paleozoic by accretion of peri‐Gondwanan terranes onto Laurentia, culminating in the formation of Pangea. During the Mesozoic, Pangea broke apart, displacing one section of the belt to eastern North America and another to northwestern Europe. These areas share aspects of their tectonic history but have been shaped differently by later Paleozoic orogenesis and Mesozoic rifting; therefore, comparisons between these regions offer an opportunity to understand which processes have been responsible for shaping their present‐day crustal structure. This study compares the crustal structure across the Laurentian and peri‐Gondwanan sutures in these regions and explores how it has been shaped by their tectonic histories. We use receiver functions with harmonic decomposition to analyze the geometry of Laurentia, Ganderian and Avalonian crust beneath Ireland and Britain and compare them with New England, northeastern USA. The Laurentian crustal thickness beneath Ireland and Britain ranges from ∼26 to 32 km, whereas that of the peri‐Gondwanan terranes varies from ∼32 to 38 km. Our analysis also provides insight into dipping interfaces and anisotropy near the Moho, which vary considerably across the study area. In contrast to our findings in Ireland and Britain, beneath New England Laurentian crust is significantly thicker (∼44 km) than accreted terrane crust (∼32 km). We hypothesize that Mesozoic rifting led to significant thinning of Laurentian crust beneath Ireland and Britain, and that regionally specific orogenic processes during the middle and late Paleozoic controlled the evolution of accreted terrane crust differently in these areas.