352 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1962 



stances of light seen during earthquakes. The slight overelaboration 

 of the report indicates a possible element of invention. The phenom- 

 enon is probably psychological in nature, but it certainly merits 

 study. 



GEOLOGY 



The geology of the southern part of Chile is largely unknown in 

 detail. Muhoz-Christi [12] has discussed the region, and, recently, 

 Sr. Luis Aguirre of the IIG has compiled a map of the outstanding 

 features of the region. An excellent discussion of the orography 

 is to be found in Fuenzalida [13]. 



At latitude 37l^° S. the country consists, on the Arauco Peninsula, 

 of Tertiary marine, estuartial, and continental deposits placed, it ap- 

 pears, unconformably over schists and phylites of unknown but pos- 

 sibly Pre-Cambrian age. These sediments contain most of CMle's 

 coal. The peninsula is cut every few kilometers by strong northward- 

 trending faults of varymg vertical displacement. The largest of 

 these, the Arauco fault zone, may be followed from Concepcion across 

 the peninsula as a discontinuous break. A branch of this fault passes 

 to the west of Lago Lanalhue, the lake being dammed by uplift 

 of the peninsular block along this fault. 



The Santa Fe fault zone, actually an ancillary member of the 

 Arauco fault zone, passes through the town of Lebu. It shows clear- 

 out strike-slip topography, modified, of course, by the deeply 

 weathered colluvium. This zone almost certainly moved during the 

 earthquake or during an aftershock. Small landslides developed 

 along its length, and cracks could be seen from the air on the hills on 

 either side. The bridge crossing the Rio Lebu was ruptured over 

 the fault zone, but, unfortunately, no record was made of the displace- 

 ment before repairs were made. 



The faulting in the Arauco Peninsula is exceptionally well devel- 

 oped, and when aerial photographs or good maps are available, it will 

 be an important area to study. Some idea of the complexity of the 

 f au] ting may be had from Fenner and Wenzel [14] . 



To the eastward, in the Cerros de Nahuelbuta, one encounters the 

 southern end of the coast-range batholith of probably mid-Cretaceous 

 age. This batholith terminates at about Traiguen (fig. 1). South- 

 ward, except for miniscule outcrops south and west of Corral, the 

 batholith does not reappear in the coastal hills for 7 degrees of latitude. 

 The coast range is cut by a number of north-south faults of consider- 

 able extent. These form the boundaries of the central valley. 



One gigantic fault passes near the town of Lumaco (fig. 1) and is 

 very notable because of the complex geomorphology of the region. 

 The Rio Lumaco flows into a closed basin, forming a large, swampy 

 area. The basin is bounded on the east by the Lumaco fault. This 

 fault is almost invisible from the ground but is quite obvious from the 



