Heat Flow 



Heat flow data were abstracted from the references shown in Figure 

 2. Values are in heat flow units (HFU) , each unit being equal to 10~6 

 cal/cm"^ sec. 



Magnetics 



Magnetic total intensity data were collected with proton pre- 

 cession magnetometers on all tracks shown in Figure 2 with the excep- 

 tion of tracks 15 and 16. Data for these lines were collected with the 

 Vector Airborne Magnetometer (VAM) described by Schoensted and Irons 

 (1955). A detailed analysis of this vector data will be given in a 

 later section. Accuracy of the proton precession magnetometer is + 1 

 nt, while that of the VAM is + 15 nt in total intensity. 



The magnetic data distribution was inadequate for the preparation 

 of a contour chart, and only profiles are shown in this report. The 

 profiles are residual (or anomalous) data obtained by subtracting the 

 International Geomagnetic Reference Field (IGRF) 1975 (lAGA Div. I Study 

 Group, 1976), corrected for annual change to the date of the obser- 

 vations, from the observed magnetic values. 



Due to an inadequate description of the annual change in some 

 areas, caused by the unrealistic coefficients used in the IGRF, long- 

 wavelength positive or negative anomalies with amplitudes of up to 

 several hundred nanoteslas may be introduced into the residual profixes. 

 An illustration of this problem may be found in Bracey (1968) . To 

 correct the problem, an arbitrary value (determined visually) was added 

 to the IGRF so that the resultant residual profiles were evenly 



