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DSDP samples from the Blake-Bahama Basin provided an opportunity to study tetrapyrrole geochemistry in sediments of Miocene and Cretaceous age. Miocene samples from Legs 40 and 41 contained chlorins similar to those found in this study (Baker, et al., 1978a, b). Earlier studies of upper Tertiary marine sediment samples contained mixtures of chlorins, free-base, and nickel porphyrins (Smith and Baker, 1974; Baker and Smith, 1975a; and Baker et al., 1976). Cretaceous sediments of marine origin have been found in some instances to contain chlorins (Baker et al., 1978b; Palmer et al., in press), but more frequently contain mixtures of free-base porphyrins, nickel porphyrins, and sometimes vanadyl porphyrins (Baker and Smith, 1975b; Baker et al., 1978 a, b). From this survey of earlier data, it becomes apparent that finding chlorins as the predominant pigment is somewhat unique for Cretaceous sediments, especially where the depth of burial is 840-960 meters. In the other two cases, Legs 41 and 43, Cretaceous sediments containing chlorins were found at 450 to 880 meters and 414 to 787 meters, respectively (Baker et al., 1978b; Palmer et al., in press). In this study, 12 Site 391 sediment core samples ranging from Pleistocene to Upper Jurassic were analyzed for tetrapyrrole pigment content. The two most striking findings were (1) the predominance of chlorins over free-base and/or metalloporphyrins and (2) the concentration versus an age-depth profile which shows that the bulk of the pigment occurred in one Miocene (391A-13) and one Cretaceous (391C-10) interval. EXPERIMENTAL Methods used for extraction, isolation, and characterization of geo-pigments have been presented previously (see DSDP Initial Reports, Volumes 38, 40, and 41: Baker et al., 1976, and 1978a, b). Briefly, 100 grams of frozen core sample were ball-milled in acetone:methanol (9:1) with several solvent changes until the extract was virtually devoid of pigment. The crude extracts were chromatographed on Sephadex LH-20 and eluted with THF. The type and amount of pigment was recorded (see Table 1). UV-visible spectra were recorded using a Beckman ACTA CIII scanning

Miocene and Cretaceous Tetrapyrrole Pigments from Leg 44, Site 391