Abstract
The BASE (Barberton Archean Surface Environments) scientific drilling project aimed at recovering an unweathered continuous core from the Paleoarchean Moodies Group (ca. 3.2Ga), central Barberton Greenstone Belt (BGB), South Africa. These strata comprise some of the oldest well-preserved sedimentary strata on Earth, deposited within only a few million years in alluvial, fluvial, coastal-deltaic, tidal, and prodeltaic settings. They represent a very-high-resolution record of Paleoarchean surface conditions and processes. Moodies Group strata consist of polymict conglomerates, widespread quartzose, lithic and arkosic sandstones, siltstones, shales, and rare banded-iron formations (BIFs) and jaspilites, interbedded with tuffs and several thin lavas. This report describes objectives, drilling, and data sets; it supplements the operational report. Eight inclined boreholes between 280 and 495m length, drilled from November 2021 through July 2022, obtained a total of 2903m of curated core of variable quality through steeply to subvertically dipping, in part overturned stratigraphic sections. All drilling objectives were reached. Boreholes encountered a variety of conglomerates, diverse and abundant, mostly tuffaceous sandstones, rhythmically laminated shale-siltstone and banded-iron formations, and several horizons of early-diagenetic silicified sulfate concretions. Oxidative weathering reached far deeper than expected. Fracturing was more intense, and BIFs and jaspilites were thicker than anticipated. Two ca. 1km long mine adits and a water tunnel, traversing four thick stratigraphic sections within the upper Moodies Group in the central BGB, were also sampled. All boreholes were logged by downhole wireline geophysical instruments. The core was processed (oriented, slabbed, photographed, described, and archived) in a large, publicly accessible hall in downtown Barberton. A geological exhibition provided background explanations for visitors and related the drilling objectives to the recently established Barberton Makhonjwa Mountains World Heritage Site. A substantial education, outreach, and publicity program addressed the information needs of the local population and of local and regional stakeholders.
| Original language | English |
|---|---|
| Pages (from-to) | 129-172 |
| Number of pages | 44 |
| Journal | Scientific Drilling |
| Volume | 33 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 18 Jun 2024 |
Bibliographical note
Publisher Copyright:© 2024 Christoph Heubeck et al.
Funding
We enthusiastically thank the ICDP Operations Support Group for continued help and advice through speedy advice, software and infrastructure over many years. The project would have been impossible to run without the legal, administrative, and financial guidance and activities of CIMERA (South Africa's consortium for research drilling) and its staff, led by its former chair, the late Nic Beukes. We thank the University of Johannesburg for logistic support. The Council for Geoscience, South Africa, provided in-kind support by hyperspectral imaging. The goodwill and permits by the authorities of Barberton, Mbombela Municipality, Mpumalanga Province, the WHS administration, and the local development company BATOBIC are gratefully acknowledged. Landowners, including the Mountainland Trust, SAPPI, Barberton Mines, and the Vos Brothers are thanked for allowing access to and drilling on their private land. Many members of the Barberton community, including schools, businesses, and private citizens, provided excellent and timely services, volunteered their services, and were gracious and interested hosts. We thank the drilling contractor and its team for its dedication in the face of adversity. The BIAS Hall, owned by the Mpumalanga Province Department of Arts, Sports, and Culture and administered by the Barberton Regional Museum, was a perfect location to combine core processing with outreach activities. Staff of the Barberton Community Tourism office helped and advised in many day-to-day questions. Astrid Christianson provided professional community hospitality and made sure that all of us found in Barberton a "home from home". A full list of the BASE staff is available in the operational report (Heubeck et al., 2024a).
| Funders | Funder number |
|---|---|
| National Aeronautics and Space Administration | |
| Council for Geoscience, South Africa | |
| Mountainland Trust, SAPPI, Barberton Mines |