(1) The clay pebble bed of Ancon (Ecuador) is essentially a true deposit, probably formed, in the first place, by the denudation of an Eocene land surface under abnormal climatic conditions.

It has not been formed primarily by overthrusting or shearing, although these tectonic phenomena have undoubtedly affected the deposit at a later stage of its history.

(2) The clay pebble bed does not attain a thickness of more than three hundred feet, and it is included in about eighteen hundred feet of uniform clay shales and sandstones. The evidence collected from the drilling of boreholes suggests that recumbent folding has taken place in this area. No other explanation can satisfactorily account for the presence of two (or three) phases of the clay pebble bed in the same borehole. (Fig. 1.)

(3) Whilst stratification is not usually present in the clay pebble bed, a certain linear arrangement of the constituent materials has been detected which indicates a flowage in the deposit prior to consolidation. Later folding, however, has obliterated most of the evidences of original accumulation.

(4) Irregularities in the present attitude of the clay pebble bed and its associated strata (such as, for example, the upper limit of the clay pebble bed transgressing the bedding planes of the superincumbent strata, the upper limit apparently being a thrust plane from which minor thrusts branch into the upper block, the presence of transitional stages, etc., where the tearing away of the sole of the upper block is visible) can all be explained by an appreciation of the special tectonics of this area, which includes the theory of recumbent folding.