A composite reference section for terminal proterozoic strata of southern Namibia

Area of Science:

• Geology
• Paleoclimatology
• Stratigraphy

Background:

• Terminal Proterozoic to Cambrian strata are crucial for understanding Earth's history, including major climate shifts and the evolution of life.
• Namibia's Witvlei and Nama Groups offer a unique, well-preserved record of this critical time period.
• Precise chronostratigraphic calibration is essential for global correlations.

Purpose of the Study:

• To construct a composite reference section for terminal Proterozoic to Cambrian strata in Namibia.
• To calibrate terminal Proterozoic chronostratigraphy using integrated stratigraphic data and age constraints.
• To reconstruct the carbon-isotope variability of seawater during the post-Varanger period.

Main Methods:

• Integrated sequence stratigraphic and chemostratigraphic analysis.
• U-Pb zircon geochronology for precise age dating.
• Correlation of stratigraphic units with global reference sections.

Main Results:

• A composite reference section for Namibia's terminal Proterozoic to Cambrian strata was established, including two distinct glacial horizons.
• Four carbon-isotope chemostratigraphic intervals (Npg, Pr, Pf, I) were identified, reflecting significant seawater chemistry changes.
• The end of the younger Varanger glaciation was dated to a maximum of 564 Ma, 25 million years younger than previous estimates.

Conclusions:

• The Namibian reference section provides a high-resolution record of environmental change across the Proterozoic-Cambrian boundary.
• The identified carbon-isotope intervals are globally recognizable, aiding in intercontinental stratigraphic correlation.
• Revised dating of the Varanger glaciation has significant implications for understanding the pace of environmental change leading into the Cambrian.