Although the burial depths of the samples are <700 meters below seafloor (mbsf) and seafloor temperatures are generally low, it was considered that temperatures may have been sufficiently high to cause increased reflectances because of the observed nonbrittle mode of basin subsidence (e.g., Driscoll and Karner, 1998). Further, it was recognized that variation within some of the types of wood tissue (Kantsler and Cook, 1979; Cook and Kantsler, 1980) could also be an important factor in measuring temperatures. In extreme cases, some types of woody tissue are unsuitable for measurement of vitrinite reflectance as an indication of maturation level. These tissue types include suberinite and the tissues preserved as jet. In practice, the presence of low-reflectance cell walls proved to be an important factor for the present suite of samples.
In addition to the reflectance data, interpretation of maturation levels is supported by the (1) presence of fluorescing liptinite and the fluorescence colors, (2) degree of compaction of woody cell structures, (3) mineral matter fluorescence intensity and color, and (4) the organic facies present.