Day 2: Monday, February 17th, 2020

Day 2: Monday, February 17th, 2020 - Barberton Geotrail ⛏





Today was a cloudless and sunny day. We woke up and had sandwiches for breakfast. We looked at Barberton Greenstone Belt, the Dwars River Heritage Site, and Transvaal Supergroup.

Stop 1: Msuali/Bulembu

Asbestos mines located here. Typically asbestos mines are easier to remediate because there is no acid rock drainage.

On the South African side of the Eswatini border the space that was once occupied by the asbestos mine has been revegetated and was overall reclaimed much better than the asbestos mine on the Eswatini side due to stricter regulations. There we also saw vesicles on the inside of pillow lavas.

Stop 2: Msauli Chert

Black chert is carbon rich. C and S isotopes are lighter indicating biological activity. Chert with concoidal fractures. It is strong, sharp, and homogeneous. It was deposited slowly in a low energy, deep water environment. There were also pillow lavas indicating a deep sea environment with less violent eruptions. 

Stop 3: Banded Iron Formation

3.3-3.2 Ga old. Iron oxides (primarily hematite) and minor chert (stretched chert nodules). It is the bottom of the sequence. It’s formed by the decomposition process conducted by bacteria that use iron.

Stop 4: Tsunami Comglomerate

3.23-3.26 Ga old. Underwater, extremely high energy environment. Sediments may not have been completely lithofied when they were disturbed. There is a slight curve in some of the sediment layers but it isn’t very uniform so it likely is not related to tectonic activity. The deformation could also be from a meteorite impact or a volcanic eruption, but the large tsunami theory is more favoured. 

Stop 5: Barite deposit (white rock) from the Archaean. No photos from the field. 

Stop 6: Angular Unconformity

3.21 Ga. Tectonics were still unstable at this time. Bedded chert and rounded conglomerates which were deposited in a high energy river delta. 

Stop 7: Moodie Group

3.20 Ga. White sandstone Tidal environment: fall of sea level or uplift of the crust. Crossbedding can be seen in the rock as evidence of an ancient stream and it is the oldest preserved tidal environment. 

Stop 7.5: Snack stop

Stop 8: Bushveld Complex

The largest mafic intrusion. Layers vary in thickness from a couple centimetres to tens of centimetres. 

Stop 9: Top of the section. Magnetite and small droplets of magnetic magma in notice host rock. 

After the Geo Trail we arrived at Thandabantu and had South African beer and steak for dinner.