The New York–Alabama Lineament Revisited

The New York-Alabama (NY-AL) lineament was originally defined by King and Zietz (1978, Geology) as a fundamental magnetic anomaly that delineates a major crustal boundary in the eastern United States. It separates a mottled pattern of dome-and-basin shaped magnetic highs and lows (mostly associated with the Midcontinent granite-rhyolite province, MCGRP; and Neoproterozoic mafic bodies) to the NW from NE-SW trending magnetic lineaments of the Appalachians to the SE, and loses definition at the NE corner of Alabama. New digital aeromagnetic maps covering the southeastern United States (AL, FL, GA, TN, SC, and NC) allow much better resolution of fine- and coarse-scale crustal domains, as well as their internal structure and boundaries, and express the southern continuation of the NY-AL lineament where associated basement rocks lie beneath the Gulf Coastal Plain sedimentary cover in west-central Alabama. Across Alabama, the magnetic lineament becomes progressively muted with increasing depth of Coastal Plain basement, but it maintains the demarcation between the distinct MCGRP and Appalachian anomaly patterns. The NY-AL lineament likely reflects a crustal scale strike-slip fault. The geophysical maps do not present obvious structures that are cut by this remarkably straight lineament. Some mafic rocks west of the lineament might be Keweenawan based on at least one drill hole in TN (Ladd well) that penetrated massive gabbro lying along a string of mafic bodies that can be tracked through KY and northward to the proper Keweenawan in MI.