Details

Autor(en) / Beteiligte

• Mcbride, John H
• Nelson, K. Douglas
• Meissner, Rolf
• Brown, Larry
• Franke, Wolfgang
• Seifert, Friedrich
• Dürbaum, Hans‐Jürgen
• Fuchs, Karl

Titel

Deep Seismic Reflection Constraints on Palaeozoic Crustal Structure and Definition of the Moho in the Buried Southern Appalachian Orogen

Ist Teil von

• Continental Lithosphere: Deep Seismic Reflections, 1991, p.9-20

Ort / Verlag

Washington, D. C: American Geophysical Union

Erscheinungsjahr

1991

Quelle

Wiley Online Library All Obooks

Beschreibungen/Notizen

• Experimental reprocessing of COCORP deep seismic reflection data collected over the buried Southern Appalachian orogen (southeastern USA) provides a more accurate characterisation of middle/lower crustal structure and Moho, thus allowing a quantitative basis for geologic interpretation. Reprocessing and migration of data over the late Palaeozoic suture (Alleghanian≈Hercynian) between North America and relict west Africa reveal varying north‐vergent thrust geometries including ramp‐and‐flat, antiformal, and planar structures. Interpretation of a strike‐parallel line over the suture zone implies that the suture is dominated by discrete bands of south‐dipping thrusts which are expressed, in strike view, as a “layered” fabric of sub‐horizontal reflections. The internal structure of the suture zone varies dramatically along strike becoming broader and less steep eastward across the Atlantic Coastal Plain as the amount of crustal “overlap” between relict west African and North American terranes progressively increases. Suture‐zone reflections are abruptly truncated in the lower crust by a ubiquitous sub‐horizontal reflection Moho which is anomalously shallow generally at 33–36 km (relative to a much deeper Moho beneath the Blue Ridge and Inner Piedmont to the west). The character of the reflection Moho varies throughout the area and, after deconvolution and frequency filtering, appears either as a simple doublet/triplet or more complex multicycle event. This multicyclic character may be suggestive of magmatic underplating by mafic igneous sills intruded during a regional thermal event brought on by early Mesozoic extension and crustal thinning related to the initial rifting and opening of the North Atlantic. The broad correspondence between a highly reflective Moho underlying thinned crust and the region of early Mesozoic rifting, together with its horizontal truncation of Palaeozoic suture‐zone structure, suggests that the Moho is a dynamic boundary that is early Mesozoic in age and was produced by rifting processes.