Black shales preserve critical records of paleoclimate and carbon cycling, reflecting coupled interactions within the Earth system and serving as key archives for Earth system evolution and unconventional hydrocarbon accumulation. At the global scale, terrestrial black shales are episodically distributed through the Phanerozoic, indicating sensitivity to long-term environmental boundary conditions. This study compiles and analyzes the global temporal distribution of terrestrial black shales, revealing a potential chronological correlation with the ∼30 Myr vertical oscillation of the solar system through the Galactic plane. It is hypothesized that during midplane crossings, perturbations from spiral density waves enhance cosmic ray flux, increasing the frequency of extreme geological events and glacial climates, which inhibit deposition of black shale. In contrast, when the solar system resides away from the Galactic plane, reduced cosmic ray flux, warmer and more stable climates, rising sea levels, and enhanced oceanic anoxia create conditions favorable for widespread black shale deposition. At shorter astronomical timescales (10³–10⁶ years), case studies from the Lucaogou Formation (Junggar Basin), Chang 7 Member of the Yanchang Formation (Ordos Basin), and the Shahejie Formation (Bohai Bay Basin) exhibit well-defined orbital cyclicity. Eccentricity and obliquity cycles likely modulated regional humidity, lake level fluctuations, and primary productivity, thereby exerting a significant influence on organic carbon burial. Future research should focus on improving astronomical forcing analysis methods, integrated Earth system modeling, and reconstruction of deep carbon cycle dynamics to develop a unified framework for black shale formation and preservation.
Jin et al. (Wed,) studied this question.