Combined compaction and heating experiments conducted with in-situ modern carbonate sediments produced dissolved and undissolved tarry hydrocarbons. During heating at temperatures ranging from 100° to 200°C (212°-392°F) and under pressures of up to the equivalent of 13,000 ft (4,000 m) of burial, hydrocarbons with an immature, biologically related, bimodal carbon distribution were converted to hydrocarbons with a relatively more mature unimodal distribution. The new hydrocarbon distribution resembles those typical of Upper Cretaceous carbonate-rock extracts in south Florida. The data from these short-term experiments lend support to the idea that limestones can serve as hydrocarbon source beds and that compaction, both mechanical and chemical (i.e., pressu e dissolution), could provide the "driving force" for expulsion into a carrier bed or directly into a reservoir. The suggestion is made that, at depths and temperatures at and within the oil-generation window, liquid hydrocarbons together with compaction waters escape during chemical compaction (akin to stylolitization). As temperature and pressure increase, liquid hydrocarbons escape through hydraulically formed microfractures. Finally, with continued burial and increased temperature, below the oil-generation window, the residual hydrocarbons and other hydrogen-rich materials (kerogen) are converted to and escape as gas condensates and gases.