In my recent post on the Diprothomo platensis, I mentioned among the evidence put forward by Argentine archaeologist and paleontologist Florentino Ameghino, the presence of "eoliths" (crude stone tools with an Oldowan appearance), and also, baked earth, which he attributed to the activity of hominins in the Miocene Pampas.
Today's post will look into the baked earth and the different theories about its origin, following, and expanding the interesting work by Pasquali and Tonni, 1998.
There is a discontinuity in the sedimentary cliffs along the coast of Buenos Aires province, where, as a layer in the Cenozoic terrain there are chunks of spongy-like, dark rock-like fragments 3 to 10 cm in size (2.2 to 4 in), they are called escorias or slag, very similar to volcanic cinder and, accompanying them there are brick-like rocks, in different shapes and sizes which were named tierras cocids or baked earth. They seem to have been formed by applying intense heat to the soil.
Hearths
Florentino Ameghino suggested in 1881 in his work The antiquity of man in the Plata (see p. 240) that they were the outcome of cooking clay in a hearth, man made artifacts, and took them as proof the ancient presence of humans in the age of the megafauna (remains of extinct glyptodonts are found in this layer).
Ameghino asks what do the fragments of baked earth "indicate? Are they the products of the first experiments in ceramic art, or are they simply the result of the action of fire from a hearth lit by humans in the time of the Glyptodon? We believe that the latter supposition is the most plausible, since the humans who inhabited Europe during the later Quaternary period did not know the art of pottery. It would therefore require more than just goodwill to admit the existence of a potter contemporary with the Glyptodon."
Prairie Fire
Later, in 1907 he explained the origin of the baked earth by assuming that human beings deliberately set the dry grasses of the Pampa prairies alight, to make hidden prey escape, and hunt them. The fire spread quickly and the grass turned into ashes fast but the roots, below the surface kept on burning for days, causing the clay in ths soil to acquire a brick-like appearance.
But, Ales Hrdlicka, 1912 who came to Argentina to validate (actually to criticize and erase) Ameghino's theory of the Tertiary man, originating in South America, also studied the baked earth. Read the conclusions of Hrdlicka in his Early man in South America, 1912 Smithsonian Institution, Bureau of American Ethnology Bulletin which dedicates its Part. IV to the "Tierra Cocida, Scoriae" (p. 45-98).
A geologist in his team, Whitman Cross (p.47) conducted controlled burns and found no effect on the soil or subsoil. However, Bailey Willis, part of the same team, inspected a plot of land which had burned recently and found brick-like structures in the soil, and remarked (p. 48) that "There is nothing, however, to connect the burnt earths of the Pampean with man, so far as the occurrences were observed by the writer. Any fire whatever, whether originating in spontaneous combustion, in lightning, or in other natural conditions, independent of man, would have the effect of burning the earth under favorable conditions"
The samples were tested (see Part V, p. 88) and the results showed they had been subjected to temperatures ranging frmo 850°C to 1050°C. The cinders or escoria were found to be non-volcanic, these glassy particles were formed by the melting of certain minerals found in the loess of the Pampas at temperatures above 1050°C.
Much later, in 1971, Césear Cortalezzi proposed that the cinders were formed by chemical reactions in the soil, involving acidity and minerals in the loess.
Volcanic origin
Outes, Delachaux and Bücking had proposed in 1915 a volcanic origin: "General Conclusions. 1 The cellular-structured scoriaceous materials extracted from Monte Hermoso and other deposits are andesitic lava scoria. 2. The compact, red, brown, or grayish materials previously considered "fired earth" are mostly eruptive tuffs."
However, there are no volcanoes in the Pampas, the closest are in the Andes, in Neuquén and Mendoza and Neuquén provinces, over 860 km (530 mi.) west of Monte Hermoso (see the location of this site in Google maps).
The authors overcome this problem by citing Charles Darwin: "Numerous, small, well rounded pebbles of pumice lie scattered both on the plain and sand-hillocks: at Monte Hermoso, on the flat summit of a cliff, I found many of them at a height of 120 feet (angular measurement) above the level of the sea. These pumice pebbles, no doubt, were originally brought down from the Cordillera by the rivers which cross the continent, in the same way as the River Negro anciently brought down, and still brings down, pumice, and as the river Chupat brings down scoriæ: when once delivered at the mouth of a river, they would naturally have travelled along the coasts, and been cast up, during the elevation of the land, at different heights" (Source).
Meteor Impact
Another explanation published by Schulz et al., 1986, in Science (A 3.3-Ma Impact in Argentina and Possible Consequences) suggested an impact origin: a meteor hit the Earth around 3 million years ago. This team had previously studied the craters of a meteorite that struck the ground ~4000 years ago in Río Cuarto, Córdoba, Argentina and found the cinders similar to those found in the baked earths. They found a mineral formed by zircon dioxide which requires a temperature of 1700°C, which is far to high to be produced by burning grasses.
The dating of the cinders led Schulz to believe that a meteor struck the region close to Buenos Aires province 3.3 million years ago, and as there is no visible crater, they conjecture it impacted the now submerged continental shelf close to Miramar or Mar del Plata, in Buenos Aires province (see map below, from their paper). This event was catastrophic: "[the
age of the deposits coincide with a pulselike change in the deep-sea stable isotopic record, reflecting a sudden change in climate and ocean circulation. These coincidences suggest that the impact may have directly induced regional faunal extinctions or triggered broader environmental changes leading to ecosystem collapse in Argentina." If there were Tertiary humans in the area, they would have been wiped out.
Conclusion
Whether we believe or not in the Tertiary man proposed by Ameghino, or in an early peoping of America by non-Homo-sapiens people, the question of baked earth has puzzled scholars for over 140 years. The explanations are interesting, some more formal than others. My preference is the meteoric impact. I don't think that it has a volcanic origin, or that wildfires of prairie grasses caused the baked earth.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall ©
No comments:
Post a Comment