Current Status and Challenges of Methyltrimethyltridecylchromans Research in Source Rocks and Crude Oils.

Methyltrimethyltridecylchromans (MTTCs) are structurally similar to tocopherols, which were identified in large numbers of source rocks and crude oils (Pleistocene to Early Cambrian). The occurrence of MTTCs was widely used as a proxy indicator of paleosalinity in the field of organic geochemistry. However, their origin and geological formation pathway still remain greatly debated. Here, we review the progress made over the past 30 years in the distribution and origin of MTTCs and their applications. Furthermore, we discussed several key points for future studies on MTTCs.