This paper reveals a previously unrecognized bias in the marine sediment record, challenging conventional interpretations of long-term carbon sequestration and weathering trends. While biases in the fossil and geological records are well-studied, this study demonstrates that deep-sea sedimentation data are also systematically skewed, necessitating a critical reevaluation of widely used paleoceanographic proxies. As a comprehensive meta-analysis of marine core data, these findings have far-reaching implications, highlighting the need to account for age-dependent biases in sedimentation-related proxies to refine our understanding of Earth's past climate and carbon cycle dynamics.