The EARTHBLOOM project focused on three billion year old carbonates that are mostly found in Northern Canada, one of the few places on Earth where rocks of this age are preserved.
The EARTHBLOOM project is using multiple diamond drill cores, donated by a gold mining company, to study the architecture and chemistry of one of Earth’s oldest carbonate platforms, preserved in the Red Lake area, Ontario. These drill cores have now been carefully examined and a detailed stratigraphic log established that describes the nature and thickness of the carbonate rocks and their relationships to other lithologies in the cores. These drill cores have also been extensively sampled and analyzed for chemical signatures that provide insight into carbonate mineral precipitation processes, the chemistry of the seawater in which they were precipitated, in the availability of nutrients in ancient seawater, and whether there was free oxygen being produced at the time of carbonate precipitation. Data from the drill cores has been supplemented with samples obtained from field work in the Red Lake area, where mapping and surface observations provide additional insights into the architecture of this unique deposit. The EARTHBLOOM project examined other sites of similar age in Northwestern Ontario where stromatolitic carbonates are found in abundance, in order to better understand the full extent of carbonate precipitation at this time, and the diversity of habitats and the primitive photosynthetic life that occupied them.
The EARTHBLOOM project has obtained several important results. These include (1) confirmation that Northern Canada really does hold Earth’s most ancient thick occurrences of carbonate minerals, as well as abundant fossilized photosynthetic microbial communities (stromatolites), (2) that these communities were diverse, forming a variety of carbonate structures in a wide range of settings, (3) that abundant associated sulfur minerals were derived from surface reservoirs and show chemical signatures of both atmospheric and biological processing, (4) that chemical records of carbon cycling are rather unusual in these communities, and indicate that some of these microbes may have acquired their carbon using somewhat atypical biological pathways, and (5) that free oxygen was sometimes present in shallow seawater, but was generally scarce. This latter point is especially interesting considering that on the modern Earth, only oxygenic photosynthesis is generally considered an important driver of carbonate mineral precipitation.
