The Gariep Belt

Overview

The CGS Field School has been mapping the Gariep Belt since 2008 in an attempt to gather accurate field data across this orogenic zone. It is envisioned that this data will be used to produce a special edition Gariep Belt map. The Gariep Belt is an arcuate orogenic belt that extends several hundred kilometers from southwestern Namibia, into northwestern South Africa. The Gariep Belt can be subdivided into two separate terrains, namely, the Port Nolloth Zone and the Mamora Terrain. The Port Nolloth Zone consists of various sediments and volcanics that were deposited in a passive rift margin.

Simplified map of the Gariep Belt (within the stippled lines); note the field area for the Field School 2014 (yellow)

Mamora Terrain

The Mamora Terrain is considered to be an allochthonous zone, comprised of several tectonic units. These include (from lowermost to uppermost): The Schakalsberge (mafic volcanic rocks and dolomite), Oranjemund (turbidites) and Chameis Complexes (mafic rocks of intra-plate and mid oceanic ridge origins). The units making up the Mamora Terrain was thrusted onto the Port Nolloth Terrain in a east-southeast direction during the formation of the Gondwana supercontinent (ca. 545 Ma). The 2014 Field School will have minimal exposure to the Mamora Terrain and rather focus on the Port Nolloth Zone.

The Port Nolloth Zone

The Port Nolloth Zone comprises of rocks that were deposited in a volcano-sedimentary rift graben associated with the breakup of the supercontinent Rodinia. Here, periods of sedimentation was accompanied by periods of volcanism, as evident by the abundance of sedimentary rocks closely associated with volcanics (as will be seen during the field school, specifically within the Vredefontein). As the rift continued to evolve, together with a marine facies change associated with sea-level rise, a rising fault scarp led to the deposition of alluvial-fan type rocks. These now make up the bulk of the Stinkfontein Group. Shallow marine conditions prevailed along the continental margin of this rift basin, allowing for the deposition of carbonaceous rock, namely the Hilda Subgroup. The history of this region can be capped off with the development of a glacial event. This led to the deposition of the Numees, and the earlier Kaigas (prior to the Hilda Subgroup). The former being demarkated as a Tillite, and the latter a glacial diamictite. Later, associated with the formation of Gondwana, was the emplacement of the Kuboes pluton (based on field evidence, syn-post tectonic).

Simplified legend of the Port Nolloth Zone, with typical thicknesses shown in parenthesis

Here are a few examples of some of the rock types that will be encountered during the field school:

Lekkersing: flaggy quartzite (base of the Stinkfontein marked by a thick conglomerate)
Vredefontein: quartzo-feldspathic arenite, phyllite, volcanic (basalt, tuff)
Kaigas: diamictite
Pickelhaube: limestone, dolomite
Wallekraal: siliclastic rocks
Numees: tillite (sheared diamictite), iron stone (Jakkalsberg Member)
Holgat: metapelite, feldspathic arenite, conglomerate, limestone (Bloedrift Member)
Kuboes: granite, monzonite, gabbro

(A): Highly sheared NNMB basement; (B): Flaggy quartzites of the Lekkersing Formation; (C): Vredefontein arenitic quartzite, showing cross bedding; (D): Vredefontein amygdaloidal basalt with plagioclase laths; (E): Kaigas diamictite, with various clasts; (F): Pickelhaube limestone

2014 - Things to Bring

Here is a list of some essential items that should be brought along:

Clothing:
Duh, the obvious (boots, pants, shirts, socks, underwear, hat, sunglasses, rain jacket, jersey, cool-clothing, warm-clothing, CGS reflective vest)

Toiletries:
Sunscreen, toothpaste, toothbrush, soap, shampoo, towels, medication (if you require any medication bring it with, pharmacies are far and few between), mini first aid kit (if you have one)

Field Equipment: 
Field book (A5 works the best), pens, pencils, water bottles (up to 5 liters capacity - we should expect 40 degrees), some kind of energy mix (e.g. energade/game);

If you're unable to bring some of these items let us know: Geological compass, GPS, camera, hammer, hand lens, laptop

Other Equipment:
Might not be necessary, but good to bring with in case: Sleeping bag, pillow, mosquito repellent, laundry detergent (omo, sunlight soap), 2-prong plug

Some field clothes and equipment used by the typical geologist 

There will be an opportunity to stock up on supplies (mostly foodstuffs) on the 16 and 23 November. However, do not rely on these days as we may be unsuccessful in getting other supplies.

2014 - Participants

This a breakdown of the participants and leaders of the CGS Field School 2014

2014 - Geo Route

The CGS Field School class of 2014 will embark on a trip across all 9 provinces of South Africa, aiming to cover most of the major geological units within South Africa. The group will depart on Day 1 from Pretoria (Gauteng) on 10 Nov (07h00) driving across most of the Proterozoic Transvaal Supergroup en route to the Archean Barberton Greenstone Belt (Mpumalanga). During this day the group will encounter some of the oldest rocks on Earth and hopefully find some of the earliest forms of life. The day will end viewing some of the Archean gneisses and an overnight stay in Ermelo.

Day 2 will see the group travel from Ermelo, through the northern part of Kwa-Zulu Natal, to the Gariep Dam, near the source of the Orange River. At the Gariep Dam the group will be on a triple junction border, namely, the borders of the Northern Cape, Eastern Cape and Free State. It's worth noting that here the group will see the source of the Orange River, and later in the trip, they will uncover the final confluence of the river, near Alexander Bay. On this day, the group will see the top of the Karoo Supergroup, most notably, the Drakensberg, and some of the spectacular cliffs in the Golden Gate National Park.

Day 3 will find the group moving down the Karoo stratigraphy, ending in the underlying Cape Fold Belt (Western Cape). During this day the group will aim to see some of the world renowned fossils and trace fossils found in the upper parts of the Karoo, i.e. the Beaufort. And, later consider the contentious black shale in the lower Ecca Group and its hidden potential energy source. Finally, considering the snow-ball Earth theory, while looking at the lowest Dwyka.

The final day, Day 4 will see the group travelling through the Cape Fold Belt, encountering most if the Table Mountain Group and Cape Granites. Here the group can consider Gondwana a bit more and how mountain building occurred in this region. The trip will finally end in Cape Town, before the next stage of the Field School begins.

CGS Field School 2014: Geology of South Africa route (highlighting some of the geological stops), click to enlarge

2014 - Itinerary

This is the provisional itinerary for the Field School 2014

CGS Field School itinerary for 2014, click on image to enlarge

Introduction

Tshimane and Emmanuel discussing contact relationships within the Wolkberg sequence around Legalameetse, near Tzaneen, Limpopo.

The Council for Geoscience (www.geoscience.org.za) established the Field School in 2006. The aim of the Field School was to provide young geoscientists with adequate knowledge and skills to ensure their growth and development as a professional geoscientist. The Field School was situated in Polokwane, Limpopo (South Africa) and focused on mapping of Archean and early Proterozoic sequences within the Limpopo Province. This included the Archean Beit Bridge supracrustal Complex and its intruding Sand River Gneiss and Messina Suite (near Messina); and the early Proterozoic Wolkberg Group (near Tzaneen).

Soon, the emphasis of the field school changed from being only focused on the training of young geoscientists, to training "on-the-fly". This meant that young geoscientists would be exposed to the various skills needed to be a geologist, while participating in the production and completion of geological mapping and research projects. The first of these was the completion of the 1:50,000 mapping exercise of the Messina Sheet (Field School class of 2009).

More recently, the Field School has shifted to the Gariep Belt, within the Kibaran-aged Namaqua-Natal Mobile Belt. Over successive years, beginning from 2009, the participants of the CGS Field School systematically completed mapping projects in the Gariep Belt with the aim of producing a detailed geological map of this orogenic zone (as exposed in South Africa). The class of 2014 will now aim to complete the final piece of the puzzle when they travel to the far north of the Gariep Belt (near Sedelingsdrift, Richtersveld National Park).

This blog will try to highlight and share some of the experiences of the CGS Field School, and follow the progress of the class of 2014 as they attempt to complete the geological mapping of the Gariep Belt and learn some of the geology of South Africa.