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A NEW TEKTITE STREWN FIELD DISCOVERED IN WESTERN BELIZE

10 September 2010 2 Comments
 

Jean H. Cornec, Geologist, September 2010

Tektites represent very special events in earth’s history. The uniqueness and molten appearance of tektites has led to the hypothesis that they were of extraterrestrial origin. Chinese literature reportedly describes tektites, known as “Lei -gong-m o”, meaning “inkstones of the thunder God” as far back as 900 AD. Australian Aborigines called tektites “ooga”, meaning “staring eyes”. Their origin is a great scientific mystery but the leading theory of the day is that a tektite swarm is formed when the extreme heat and pressure generated by large meteorite or comet smashing into the earth liquefy terrestrial soil and rock and spread the resulting ejecta from the impact crater up to several hundred kilometers from the site.

This molten material would have been moving at extremely high speed through the atmosphere and space, sometimes exhibiting aerodynamically shaped “splash” form s. Tektites are usually small glassy objects which can be easily mistaken for black obsidian. These enigmatic globules are often spherically shaped with commonly pitted surface markings but they can occur in flatten or elongated round forms as well. Tektites are not found everywhere on Earth but in well defined areas called strewn fields, usually associated with known meteoric impact craters. Until now, there were only five major recognized strewn fields out of all the meteoric impact events on Earth: -Chicxulub/K-T boundary tektites (65.4 million years) -North American in Georgia and Texas (age: 35.3 million years) -Czech Republic in Moldavia (age: 15 million years). -Ivory Coast (age: 1.16 million years). -Australasian/Indochinese (age: 0.77 million years). New evidence from western Belize now points to the discovery of a sixth strewn field in an area encompassing the localities of Billy White, Santa Familia and Bullet Tree Falls (Figure 1).

The areal extent of this swarm is likely to be considerably much larger. Tektite-looking materials had previously been reported in archaeological excavations of Mayan ruins at Tikal (Essene et al., 1987; Moholy-Nagy and Nelson, 1990; Hildebrand et al. 1994; Senftle et al., 2000) located 55 kilometers to the west of Belize strewn field, and at El Pilar (Ford, 1994). For the first time there is now confirmation of natural occurrences of tektites, undisturbed from past human activities, in a region centered on Santa Familia (Cho, Cornec). These tektites usually show limited signs of weathering and transport (Figure 1a).

Figure 1: a) photograph of 14 tektites found by inhabitants of the Bullet Tree Falls & Santa Familia areas; one Belize dollar coin for size reference; b) the round-shaped specimen to the right was collected by the author in a gravel pit located to the west of Billy White village.

G. Izett (1994) dated two of the Belizean tektites at around 820,000 years old (Figure 2). This age is quite similar to the Australasian tektite swarm, perhaps an indication of multiple impacts by a binary asteroid.

Figure 2: table reproduced with permission of G. Izett. Note: tektite 94G50 is on display at the Chaa Creek Natural  History Museum.

The precise tektite-hosting stratigraphic horizon has not been specifically delineated as yet but it would be within young Quaternary sediments such as the alluvial terraces of the Belize River. It is also likely that the present-day surface of older limestone terrains located to the north of Bullet Tree Falls and Santa Familia would be identical to the tektite-bearing paleo-erosional surface from 800,000 years ago. Generally speaking tektites must have fallen near the locations in which they are found. The smootherlooking tektite collected in a river gravel terrace near the village of Billy White could have been fluvially redeposited (see figure 1b). Hunting for tektites is better done immediately after rainstorms as they shine brightly when wet.  Although the probability of preservation of impact craters in the geological record is low, considering the relatively young age of the Belize event, the site of the source crater for the Belize tektites should still be visible unless completely eroded off or buried under younger alluvial deposits.

The tektite melt would have been ejected downrange of the meteoric crater to considerable distances (several hundreds of kilometers) and landed at their present locations by ballistic flight through the upper atmosphere. Numerical modeling shows that high velocity (40 kilometers per second) impacts with impact angles of 30 to 50 degrees may be considered as the best candidates for tektiteproductive events (Artemieva, 2001). One possible candidate is a 12-kilometer diameter structure centered on the circular Pantasma valley located in the Jinotega Department of northern Nicaragua, first suspected to be a potential impact crater by V. L. Kowald in 2006 (Figure 3).

If the impact origin is confirmed, this crater would have been large enough to have produced tektites. Could an oblique asteroid impact in Nicaragua be responsible for the tektites found in Belize? This undated feature is located more than 500 kilometers to the southeast of Belize’s Santa  Familia strewn field (Fi g ure 4).

Figure 3: Shaded relief map of the Pantasma area in northern Nicaragua showing a 12km-diameter           crater-like impact structure.   Sources:  INETER and Google Earth, in L. Kowald, 2006, http://www.pantasma.com

Figure 4: Did Belize get hit by a Nicaraguan blast some 800,000 years ago? Note:  Suspected Nicaraguan source crater and Belize tektite field are highlighted in yellow in their  actual size on this Landsat TM image but the Belize tektite field is likely to be considerably much larger.

No doubt more tektites will be found in western Belize and further studies may provide fascinating insights on that mysterious visitor from outer space that created them in the first place.

 

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  • Briman said:

    Very interesting article. I have been intrigued by the Tikal tektites for some time. Now it appears the strewn field has been found. The stones are unlikely to source from the Australasian event- despite the age similarities the shapes of the samples indicate a closer source. One would expect extreme ablation similar to Australian tektites if the source for Belizian stones was the same impact…

  • Aubrey Whymark said:

    Very interesting work! A 500km distance from the possible source crater is very promising and typical for proximal splashforms.

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