A high-resolution record of early Paleozoic climate

Area of Science:

• Paleoclimatology
• Geochemistry
• Stratigraphy

Background:

• Paleoclimate reconstructions for the Early Paleozoic are limited by scarce skeletal material for oxygen-isotope analysis.
• Bulk-rock [Formula: see text] data offer wider coverage but risk diagenetic alteration.
• Assessing diagenesis is crucial for reliable paleoclimate interpretations.

Purpose of the Study:

• To evaluate the diagenetic alteration of bulk-rock [Formula: see text] in Cambro-Ordovician carbonate platforms.
• To reconstruct Early Paleozoic paleotemperatures using a global compilation of [Formula: see text] data.
• To investigate the relationship between ocean temperatures and the Great Ordovician Biodiversification Event.

Main Methods:

• Paired clumped and bulk isotope analyses of micritic carbonates from two Cambro-Ordovician platforms.
• Assessment of diagenetic alteration by comparing clumped and bulk isotope thermometers.
• Compilation and stacking of global bulk rock [Formula: see text] datasets, minimizing diagenetic effects.
• Comparison of reconstructed [Formula: see text] trends with brachiopod and conodont records.

Main Results:

• Clumped-isotope thermometers reset, but bulk [Formula: see text] showed minimal alteration due to low fluid exchange.
• Bulk rock [Formula: see text] trends align with other proxies, suggesting preservation of temporal temperature signals.
• Reconstructed paleotemperatures show Late Cambrian warming, Early Ordovician extreme warmth, and subsequent cooling.
• Evidence for transient warming and climate instability in the Late Ordovician.

Conclusions:

• Bulk-rock [Formula: see text] analysis is a viable method for reconstructing Early Paleozoic paleotemperatures, even with some diagenetic resetting.
• Ocean cooling may have influenced the Great Ordovician Biodiversification Event.
• High-resolution paleoclimate data reveal climate dynamics previously unobserved, potentially linked to tectonic activity.