Aquatic Algal Mat-Driven Precursor Fire Sphere Cycle (FSC) Hypothesis

Abstract

The long-standing absence of terrestrial photosynthetic fossils in pre-Devonian strata has led to the conventional view that continental interiors were barren of life during the Archean to Cambrian. This study challenges this view by proposing the Waterborne Soft Algal Mats Pre-Fire-Sediment Cycle (Pre-FSC) Hypothesis. We argue that from the late Archeon onward, stress-tolerant cyanobacteria and green algae, dispersed as micron-sized resistant spores by atmospheric winds, formed widespread mats in continental water bodies. These mats, lacking hard parts, were rarely preserved in situ but, through periodic low-temperature smoldering driven by wet-dry climate cycles, continuously supplied bioavailable nitrogen, phosphorus, and trace metals to the ocean. This process gradually built the material foundation for early life evolution and persistently modified the global marine ecosystem. We further propose that multiple drought pulses during the terminal Ediacaran triggered large-scale thermal pyrolysis of these mats, delivering massive nutrients to the ocean and facilitating the Cambrian life radiation. This Pre-FSC hypothesis, temporally continuous with the Devonian vascular-plant-dominated FSC model, provides a coherent framework explaining several Precambrian geological paradoxes, including the disparity between marine and terrestrial algal fossil records, Proterozoic terrigenous combustion carbon anomalies, and the formation of ancient marine source rocks.