81 Investigating Earth’s History With Continental Scientific Drilling

This session brings together research exploring Earth using subsurface geological datasets from continental scientific drilling, intended to be a broad showcase of research spanning structural geology, tectonics, natural hazards, sedimentology/stratigraphy, geothermal energy, critical minerals, deep biosphere, paleoclimatology, paleolimnology, and paleobiology.

Monday, 20 October 2025
8:00 AM - 12:00 PM
HBGCC, 214C

Resolving the origin and emergence of animals with continental drilling

Paper number: 81-3
Program: Technical Sessions
Time: 8:45 AM – 9:00 AM

Authors

Abstract

The origin of animals was a milestone in ecology and evolution. However, macrofossils provide limited insight into the early evolution of animals as they were likely small, soft-bodied, and not readily preserved. Although molecular clock analyses have suggested either a pre-Cryogenian, syn-Cryogenian, or post-Cryogenian origin of animals, these models rely on fossil calibration, which is lacking. The discovery of putative Neoproterozoic demosponge biomarkers and concomitant changes in photosynthetic primary producers have provided key data points for relating the emergence of animals with environmental changes. Yet, the age of their first appearance in Oman is at best loosely constrained to be between the end of the Sturtian Snowball Earth glaciation at ca. 661 Ma and the Cryogenian-Ediacaran boundary at ca. 635 Ma. It has alternatively been suggested that animals did not appear until later in the Ediacaran Period, after the proliferation of green algae in multiple locations.

 

With Geological Research through Integrated Neoproterozoic Drilling–Cryogenian (GRIND-CRY), we aim to resolve these uncertainties by obtaining cores through archetype Cryogenian successions in Oman, Brazil, and Namibia. In January 2026, with ICDP support, we intend to begin drilling the Neoproterozoic siliciclastic-dominated succession in southern Oman (Dhofar) near Mirbat. Outcrop studies demonstrate that these successions contain evidence for glaciation and retain organic matter that has not been heated over ~90oC. We will integrate geochemical, paleomagnetic, and sedimentological data from these cores with that from both outcrop and previously drilled industry cores. These data will provide a refined age model and paleoenvironmental context for the diversification of eukaryotic steroid biomarkers, the rise of green algae to ecological dominance and the origin of animals relative to ocean oxygenation and Snowball Earth glaciation.

 

Over the next three years, we will subsequently drill Cryogenian strata in Brazil and Namibia. Both locations preserve shelf-slope transects of a mixed carbonate-siliciclastic sequence with interstratified diamictite and iron formation, which are well-suited to a variety of geochemical studies. Although the succession in Namibia is thermally overmature, it preserves the Trezona carbon isotope excursion and hosts abundant and diverse microfossil assemblages, which will complement data from other sites.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413202

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