'; ?>
click to enlarge
162 Pardon vermouth spots! II. CONTACTS 1-2. Clearly discordant. A much later thin stream deposit on a marine series. 2-3. A marked and rather abrupt lithologic change, but probably due rather to sudden change of conditions rather than to lapse of any considerable time. In the upper part of 3 appear coarser lenses which become more numerous until the fine ss. forms lenses in the coarser, and the uppermost coarse beds are frankly marine + basal to the overlying tuffs. 3-4. This contact is nearly plane but sharp. With the highly lenticular nature of 3, a disconformity is indicated. 3-5. In places 3 overlaps 4 and has a similar contact with 5. In general, however, 3 is thickest over 4 + appears to overlap 5 only slightly. 2-5. Where 3 has wedged out, 2 contacts with 5 (apparently also in places similarly 4, but not so clear). The contact is certainly discon- formable, very sharp, generally with a basal marine conglomerate of transgression. 4-5. This contact (shown in the middle of the hill in the section but elsewhere exposed on the surface) seems to be that typical between channel beds and nearly or quite contemporaneous flood-plain beds, i.e. the channel beds in part incised + in part grading into the others. 163 4,5-6. Although the lithographic difference between 5 + 6 is slight, the contact is discordant apparently, as is that between 4 + 6. The thickness of 4 + 5 (together) varies much, 6 at times almost reaching 2 or 3, and the bedding of 4 + 5 is not always parallel to the contact. The contact is irregular. The base of both 4 + 5 is coarse, approaching sandy texture, or even gravel. There appears definitely to be a break in the series, its value, of course, only determinable from fossils or regional study. III. FOSSILS AND AGES. 1. This is a terrace gravel resting on the flat upper surface, a remnant of an erosion plain. It is lower than the original rodado deposit, the Tehuelche of the high pampa, but far above the present river level, hence probably Pleistocene. 2. The marine beds contain a large in- vertebrate fauna. A penguin bone found on the surface of the lower beds perhaps came from here, perhaps from the lower beds. In the slope of the high pampa nearby, whale bones occur. This bed is part of the Patagoniano. 2-3. The transitional cg. + ss. lenses in the base of 2 + top of 3 contain very numerous bits of bones and teeth. These are