Preliminary results from a paleo- and rock-magnetic study of Oligocene ash-flow tuffs in Socorro County, New Mexico
— William C. McIntosh

The Oligocene volcanic rocks of Socorro County include five extensive ash-flow tuffs, several subordinate pyroclastic units, and basalticandesite lavas. Within a 1400 km' area, these volcanic rocks exhibit significant potassium metasomatism. Associated with this area of metasomatism is an aeromagnetic anomaly pattern that is subdued relative to that of unaltered areas (Chapin and others, 1978, Pl. 1).

The present magnetic study was undertaken for three reasons: (1) to investigate the paleomagnetic stratigraphy and rock magnetic properties of Socorro County ash-flow tuffs; (2) to assess the potential of paleomagnetism as a tool for stratigraphic correlation of these units; and (3) to evaluate whether metasomatic alteration of oxide minerals is responsible for the subdued nature of aeromagnetic anomalies. (Editor's note: A sample location map is not included with this paper because it was written while the author was in Antarctica and his field sheets were at home.)