Regression in the middle Miocene returned Site 1193 into the euphotic zone. Subsequently, 200 m of limestones and dolostones accumulated (Fig. F2), dominated by bryozoans and LBF whose sizes and shapes indicate paleodepths ranging from oligophotic (>50 m; terminology of Pomar [2001]) to shallow euphotic (<30 m). Common occurrences of large, relatively delicate lepidocyclinids (Fig. F10A) and of large, flat Cycloclypeus (Fig. F10B) between 100 and 223 mbsf indicate relatively oligophotic conditions, probably on the order of 50–100 m. Between 40 and 90 mbsf, robust morphologies of LBF and evidence for physical damage to skeletal material (Fig. F10C, F10D) indicate shallower conditions (<30 m), which is consistent with several exposure surfaces that have been interpreted in this interval (Shipboard Scientific Party, 2002). Stellate morphologies of Lepidocyclina become increasingly prevalent uphole (F-parameter = 3–4), indicating a middle Miocene LBF assemblage (Chapronière, 1981). Other notable LBF include vermiform Miogypsina thecideaeformis (Rutten). The upper few meters (at least 36.6–37.9 mbsf) of the "platform" is characterized by reworked benthic material and exposure surfaces (Shipboard Scientific Party, 2002), whose interpretation is complicated by bioerosion during late Miocene drowning of platform facies.
Site 1194 corroborates the story of early Miocene sea level rise and middle Miocene sea level fall interpreted at Site 1193. Following early Miocene submergence (>18.2 Ma from nannofossil dates; Shipboard Scientific Party, 2002), >100 m of carbonates accumulated (264–375 mbsf) consisting of very fine bioclastics and planktonic foraminifers. The presence of outer neritic to upper bathyal benthic foraminifers indicate the deepest paleoenvironment for this site during the early and middle Miocene. At 256 mbsf, bioclastic debris, particularly bryozoan fragments, increase in size, whereas planktonic foraminifers become less dominant, indicating a shift to neritic conditions (Shipboard Scientific Party, 2002). Shoaling continues upward; at 158 m, Amphistegina spp. become abundant, indicating either euphotic depths or transport from euphotic depths in the interval between 115 and 158 mbsf. In Samples 194-1194A-16X-CC (132.9 mbsf) and 194-1194B-4R-CC (138.8 mbsf), abundant specimens of modern-appearing Amphistegina lessonii (d'Orbigny) that are normal in size (1–2 mm diameter) and intermediate in thickness, along with common Amphistegina radiata (Fichtel and Moll) and Operculina (Fig. F11), indicate water depths of ~30–50 m. Nannofossils indicate the age of this lowstand interval at between 11.9 and 13.6 Ma (Shipboard Scientific Party, 2002).
As noted previously, much of the history of Site 1196 is lost to poor core recovery and dolomitization. Nevertheless, deposition contrasts with that at Site 1193 by the striking differences in dominant macrobiota. Bryozoans dominate shallow-water carbonate sediments at Site 1193 (e.g., Fig. F10D), with red algae and LBF generally of secondary importance. Red algal fragments and rhodoliths dominate sediments at Site 1196, with corals and LBF generally of secondary importance and bryozoans relatively rare (Shipboard Scientific Party, 2002). Thus, photosynthetically driven calcification was the dominant process at Site 1196, whereas heterozoan (terminology of James, 1997) calcification was dominant at Site 1193, even though the widespread presence of LBF indicates that much of the deposition at Site 1193 occurred within the photic zone. The difference between photozoan calcification and heterozoan calcification probably accounts for why sedimentation at Site 1196 kept pace with late–early Miocene sea level rise, whereas sedimentation at Site 1193 did not.
Despite differences in dominant macrobiota between the platforms, LBF assemblages were generally similar (Figs. F7, F9, F10). One remarkable environmentally induced (facies) difference was found in lithologic Subunit IIA (Shipboard Scientific Party, 2002) at Site 1196 between 182 and 336 mbsf. In this interval of skeletal floatstones and grainstones, both large and small porcelaneous foraminifers (Fig. F12) dominate the assemblage, indicating warm shallow waters with higher carbonate saturation than any other interval seen at any site during Leg 194. The presence of visible bits of organic matter, probably remains of seagrasses, along with abundant gastropods and bivalves (Figs. F12A, F12B) (Shipboard Scientific Party, 2002), corroborate the interpretation that environmental conditions remained near sea level (<12 m). Austrotrillina howchini and Flosculinella botangensis (Fig. F12A, F12B) are abundant in this interval; these species characterize Chapronière's (1981) middle Miocene LF 8 assemblage, interpreted as 13.3–15.2 Ma. Nannofossil dates of 13.6–18.2 Ma for two samples within this interval are consistent with the LBF ranges. The thickness, age, and distinctly shallow-water nature of this interval of sedimentation indicates that the combined effects of sea level rise and subsidence provided 150 m of accommodation space in ~2 m.y. and that platform accretion kept pace. Probable exposure surfaces above this interval (Shipboard Scientific Party, 2002) suggest that this facies preceded the late middle Miocene regression.
Meanwhile, deposition at offbank Sites 1197 and 1198 was dominated by planktonic foraminifers and bioclastic calcareous silts and fine sands, principally red algal in origin, but including larger foraminiferal debris (Fig. F13A, F13B). The interval between Samples 198-1198B-18R-CC and 20R-CC (364–382 mbsf) is dated by nannofossils and planktonic foraminifers at 13.6–15.1 Ma, which is consistent with the LF 8 range of 13.3–15.2 Ma for lithologic Subunit IIA at Site 1196. Furthermore, Sample 194-1196A-19R-1, 1 cm (Subunit ID; Shipboard Scientific Party, 2002), contains a very similar LBF assemblage (Fig. F13C, F13D) to the transported LBF common between 185 and 349 mbsf in Hole 1197B (Fig. F14), which is dated between 11.4 and 13.6 Ma by calcareous nannofossils and planktonic foraminifers (Shipboard Scientific Party, 2002). Lepidocyclina (Nephrolepidina) howchini (predominantly stellate) (Chapronière 1981, 1984), M. thecideaeformis, and Operculina spp. are common to both. Amphistegina spp. and Cycloclypeus spp., including Cycloclypeus (Katacycloclypeus) annulatus (Fig. F14B), also were present in transported sediments at Site 1197.