Southern African Meteorite Recovery Program | ||
P.O. Box 2552 Cramerview 2060 |
Amateurs in the Service of Science |
Phone +27 11 886 5602 Mobile +27 83 212 8945 South Africa |
Spring 2001 Expedition
Members
Trevor Gould |
Stephan Laubscher |
Brian Fraser |
Val Fraser |
Results
More samples were returned to the University of the Witwatersrand for analysis than on the previous expedition. Of these three proved to be worthy of further analysis and Professor Uwe Reimold and Dr Paul Buchanan called for thin sections to be made. Unfortunately, they all proved to be volcanics.
Acknowledgments and thanks
The team wish to thank the South African Heritage Resources Agency for kindly providing a permit to collect any meteorite finds in specific areas, and especially Ms Mary Leslie.
Thanks also go to the Department of Geology, University of the Witwatersrand, for general and specific assistance with the expedition and its objective.
The location was clarified by Professor Bernie Moon: our thanks go to him for taking the time to help us.
We would also like to thank Stephan Laubscher, a professional geologist, for taking time out to come along and share his expertise with us.
Thanks are also conveyed to the Council for Geoscience, both in Pretoria and Upington, for assistance rendered.
Expedition Area
The search area was defined as the set of permanent dunes North of Upington and South of the Kalahari Gemsbok Park. The intention was to find locations with minimal sand, such that inter-dune areas would be essentially desert pavement and to search the inter-dune areas.
The logic of this approach was that even permanent dunes move slowly and that as they move they would absorb any meteorites and eventually deposit them on the trailing edge: i.e. the desert pavement.
Site Description
The inter-dune areas seen were extensively vegetated, and included thick sand cover. The dunes were vegetated to a higher degree than expected, but it would have been unlikely to find other than fresh falls on dune surfaces anyway.
Therefore searches were restricted to dry pan surfaces, of which there were a number in the vicinity.
The pans were of two types the most common surface was covered in gravel and boulders related to erosion of Dwyka tillite, while less commonly we found salt encrusted surfaces with similar Dwyka tillite erosional remains.
The Dwyka represents a period of continental glaciation in South Africa, and this means that the provenance of the remains was generally far distant and of widely different rock types.
This provided a rich source of many different rock types, which also had the effect of reducing the signal to noise ratio hoped for: many rocks had magnetic signatures, and demonstrated expected meteoritic features.
A reasonably large number showed black fusion crusts which proved to be desert patina. One even had a radial flow pattern on one side of a rounded dark rock, which looked just like and oriented meteorite: the radial pattern resulted from radiating dolomite crstals!
Another dark rock lay on the white salt surface [Norokei Pan] and showed regmaglypt features characteristic of iron meteorites: it is magnetic, heavy, but proved to be terrestrial.
On one salt pan [Wit Pan] which was relatively devoid of any rocks a number of tiny greenish rocks were found in what appeared to be a strewn field pattern: they were magnetic, but proved to be weathered lavas.
Expedition Diary
Saturday 8 September 2001 | Stephan and I left at 02:00. Travelled
directly to Upington. The destination was a Bed and Breakfast about 50Km North of Upington
on the road to the Kalahari Gemsbok Park. Our experience of the BnB enables us to recommend it without hesitation: the owner provided excellent local knowledge, enables contacts to be made amongst local farmers, took us around to different places and made us feel welcome. Stephan stayed at the B n B, while I camped near a pan half a kilometre away. Paul, the owner of the Kalahari Gastehuis, took us for a drive to one of his other farms past a commercial salt pan. We looked at some desert pavement areas, very complex in terms of the huge variety of rock types found, including jaspers, marble, lavas etc. The drive included a number of high speed switchbacks over the dunes, which was marvellous! We returned via the Noenieput road. |
Sunday 9 | Searched a pan [Blou Pan] to the North of the
B n B all day on another neighbours farm. The pan was covered wall to wall
with dark rocks. Later a farmer [Gysbert] and his wife arrived in their 4X4 and invited us to see their salt pan [Wit Pan]. We followed him, but the final trip to the salt pan was made on the back of the 4X4. As one travelled over seemingly endless red dunes, one suddenly came across a blindingly white pan surface stretching for kilometres in all directions. The farmer drove to the middle of the pan, dropped us off and told us hed collect us at 17:30. The salt pan experience was wonderful: the salt crust was thin a few millimetres- and beneath it was a fine soft sand. It was quite hot and the Sun reflected off the pure white surface: if it hadnt been for copious quantities of sunblock we would have been pretty badly burned. On returning in the twilight we saw a spring hare, a ring tailed mongoose and a mouse. In the evening we drove into Upington for supplies. |
Monday 10 | The Sun rose on a beautiful windless day. My
tent was parked on a red sand dune under a Shepherd Tree. There was a lot of treed
vegetation on this sand dune and below it on all sides was a dry pan. The temperature at
sunrise was about 6 degrees. The thin cirrus clouds showed high wind speeds aloft. A small family of meerkats live on the dunes. We first went to the offices of the Council for Geoscience in Upington. After lunch Stephan and I searched the commercial salt pan [Norokei Pan]. On our return to the B n B, Brian and Val had arrived. We had hoped to do some observing in the evening, but clouds appeared out of nowhere and put paid to that idea. |
Tuesday 11 | A big storm swept through the area at about
02:00. I awoke at 02:00, thirsty, and spied a can of Coke that I had left in the tent and
drank it. A few raindrops struck the tent, which flapped around in the wind. Gysbert took us to a distant pan [Filanders Pan] which we spent the morning searching on. In the afternoon we searched Bloupan. It was cold- of the order of 7 degrees, with a freezing wind. You could see the wind coming, accompanied by dust, and the most effective defense was to turn your back to it. On our return to the B n B, we heard about New York. The world had changed. We felt very sorry for the innocent victims. Stephan expressed an observation that we were never going to find any meteorite, unless we stumble across one. He felt that our time would be better spent looking at the Namaqualand flowers, on the grounds that at least the flowers were there. This observation disappointed me and left me feeling very de-motivated, but in retrospect, our task must be done. If it was easy, everyone would do it. |
Wednesday 12 | We travelled back into Upington and visited
the Upington High School, which was reported to have a meteorite. The Headmaster told us that it had been given to the school in 1940 by a farmer, and that it had become part of the school tradition. This large rock lay next to the Headmasters desk on the carpet. It proved to be magnetite. The Headmaster was advised that if one finds such things, it is always best to hand them in for analysis: then only can one be sure. In the afternoon we travelled to the farm next door to the B n B a distance of about 50Kms away to look at another reported meteorite, which also proved to be a lump of magnetite. The wind was cold and strong and blew all night. |
Thursday 13 | The cold front continued to intensify and in
the morning the temperature inside the tent was 5.7 degrees. The clouds dissipated, but
not the wind. We spent the day searching on Norokei Pan and Komkom Pan. It rained during the night, but didnt really make anything wet. Huge gusts of wind. It has been cold for almost all of our stay. |
Friday 14 | Broke camp. Watched the sun rise over the
Kalahari dunes for the last time. Went to the B n B for a bath. We went via Upington
to Augrabies Falls, where apart from the wonderful scenery, we watched CNN reporting on
the World Trade Centre. We then travelled westwards, stopping at Aggenys, then on to Springbok, where Stephan and I camped. Brian and Val stayed at the Springbok Lodge, which has a lovely mineral collection. After booking in, we all drove to Port Nolloth and watched the Sun set over the Atlantic from the deck of a supply vessel. We all observed the green flash the first time in my life I had seen it. |
Saturday 15 | Broke camp, and went to Nababeep and visited
the Mine Museum, which was good. The Namaqualand flowers were all around and provided a
magnificent specatacle. We drove South on the main road toward Cape Town, losing Brian and
Val in the process. At Vanrhynsdorp we turned off and drove over the Vanryns Pass to Calvinia, Williston, Carnarvon, Victoria West and toward Kimberley. We stopped on the side of the road for a short sleep at Heuningneskloof, a place which brought back old memories for me, then through Kimberley and back to Johannesburg. The total journey distance was in excess of 4000Kms. |
Comment
Despite the lack of success, we built some local knowledge and experience of the art of meteorite hunting.
Given one recoverable meteorite per grid 10Kms on a side, we would be within 5Km of one if we stood in the middle of the grid. This looks easy, but lets look a little more deeply.
A searcher can successfully scan 2.5m on either side and therefore searchers are spread 5m apart. On a 10Km side, there are 2000 search lines, each 10Km long. To find one recoverable meteorite, expect to walk 20 000Kms!
The grid of 100 square km. is also slightly optimistic, as the Saharan experience is one meteorite per 200 square Km.
Again, you assume that your under-trained searcher will recognise a meteorite after walking in the hot sun all day.
I am not surprised we have found nothing as yet, but the only place where success comes before work is in the dictionary.
Therefore:
Spring 2002
For the Spring Expedition, well be returning to the Upington / Kalahari Gemsbok district. The Expedition will be paired with a Deep Sky Observing Expedition, again under the auspices of the Johannesburg Centre.
Dates are: Good Friday 29 March to Sunday 7 April.
Hope you join us for this exciting Kalahari Safari!
Trevor Gould