MECHANICS OF THE GENERATION OF ANNULAR AND BLOCK STRUCTURES IN THE CRUST

Abstract

In large-scale analyses of geologic maps, many investigators have identified not only linear anomalies, but both annular and square-block anomalies. The conclusion that annular and other closed structures of various orders exist is usually based on satellite photographs of the earth's surface. There thus arises the important practical problem of determining whether the closed anomalies expressed in the topography and geophysical fields of various types correspond to any real subsurface structures, or are no more than surface images. Here we shall assume viscous flow in a lithospheric plate. In particular, we shall assume that the viscoplastic model applies to it, bearing in mind that viscous (cataclastic) flow in rock bodies begins after brittle failure (i.e., at yield point), that is, after the rock medium breaks down into blocks with effectively viscous contacts.