AGE AND LITHOSTRATIGRAPHY

In the studied vertical succession of the SMP, the same lithostratigraphic Units I (Subunits IA–ID) and II (Subunits IIA and IIB) were recognized at both Sites 1196 and 1199 by the Shipboard Scientific Party (2002a, 2002b) as well as Subunit IIIA at Site 1196 (Fig. F5). The total recovery at Site 1196 shows low percentages (Hole 1196A: Unit I = 13%, Unit 2 = 6.3%, Subunit IIIA = 1.5%; Hole 1196B: Unit I = 15.4%, Unit II = 4.5%) At Site 1199, the percentages are higher in Unit I (52.3%) and on the same order in Unit II (3.3%) with no recovery in Cores 194-1199A-22R through 29R (Fig. F5). The Shipboard Scientific Party (2002a, 2002b) correlated the two sites in a schematic diagram representing the lithostratigraphy and the architecture of the SMP (Fig. F3). This lithostratigraphic framework is based on seismic architecture (Fig. F2), facies similarities, biostratigraphy, and some noticeable subunit boundaries interpreted as possible regional surface exposures or hardgrounds (Shipboard Scientific Party 2002a, 2002b). The onboard logging stratigraphy proposed a slightly different correlation pattern based on uranium contents and resistivity of the rocks (Fig. F6). The main difference between the lithostratigraphy and the logging stratigraphy concerns the correlation of Subunit IIB between the two sites.

Unit I was dated middle to late Miocene in age by the occurrence of Lepidocyclina spp. and planktonic foraminifers of Pliocene age at the top of the SMP (Shipboard Scientific Party, 2002b). Furthermore, Subunit IIA was dated middle Miocene in age using Flosculinella bontangensis, whereas Subunit IIB was dated early to middle Miocene in age by calcareous nannofossils found in the last core of Hole 1196A (Shipboard Scientific Party, 2002b). Using the most recent foraminifer biostratigraphy of the Indo-Pacific (Boudagher-Fadel and Banner, 1999; Boudagher-Fadel et al., 2000a, 2000b), we propose to attribute a middle Miocene age to Subunit IC (Hole 1196A) based on the occurrence of Miogypsina spp.

The studied vertical succession at Site 1196 comprises seven subunits (Fig. F5).

1. The upper part of Subunit IIIA (345.8–412.7 mbsf, Hole 1196A) consists of a pinkish white to light brown dolomitic limestone. The facies results from both recrystallization and dissolution of a poorly sorted rudstone-grainstone with massive and branching corals, mollusks, and rhodoliths. The lower part of Subunit IIIA is poorly recovered. It contains some intervals of white dolomitic floatstone with common to rare rhodoliths, red algae and echinoid fragments, bryozoans, and large hyaline benthic foraminifers in a grainstone matrix. The lower boundary of Subunit IIIA is defined by the appearance of a brilliant white sucrosic dolostone in the underlying Subunit IIIB.
2. Subunit IIB (335.9–345.8 mbsf, Hole 1196A) is a poorly sorted rudstone-boundstone with massive and thick lamellar coral colonies. Rare mollusks, red algae, and miliolids were observed in a medium to coarse sand-sized packstone-grainstone matrix. The lower boundary of Subunit IIB is lithologic in nature with dolomitization of the rocks.
3. Subunit IIA (182.2–335.9 mbsf, Hole 1196A) is a poorly sorted light gray to pale brown (yellow) floatstone in a silt-sized grainstone matrix. The subunit's predominant components are large porcellaneous benthic foraminifers (alveolinids and soritids), gastropods, and unbroken bivalves including pectinids, solitary corals, and bryozoans. Coral fragments of possible secondary reef frame builders (Table T1) occur especially in the lower part of the subunit. The grainstone matrix contains abraded red algae debris and small benthic foraminifers (miliolids). Threadlike dark patches up to 1 cm long were observed in the upper part of the subunit. They were interpreted as preserved sea-grass roots (Shipboard Scientific Party 2002a, 2002b).
4. Subunit ID (162.8–182.2 mbsf, Hole 1196A; 145.0–184.9 mbsf, Hole 1196B) is a pale brown dolomitic floatstone in a grainstone matrix. Biogenic components are elongated fragments of branching red algae, rhodoliths, and large hyaline benthic foraminifers. Lamellar and branching coral fragments, bivalves, and bryozoans are also present. The lower boundary of Subunit ID corresponds to a sharp lithologic change with a thin dolomitic crust in Hole 1196B.
5. Subunit IC (125.9–162.8 mbsf, Hole 1196A; 130.5–145.0 mbsf, Hole 1196B) comprises light gray to white floatstone-rudstone and boundstone with hermatypic corals a few centimeters in size. Subordinate rudite-sized components are similar to those in Subunit ID. They are all included in a fine to medium grainstone matrix. The lower boundary of Subunit IC in Hole 1196A is described as an iron-stained, 1-cm-thick micritic crust (Shipboard Scientific Party, 2002b).
6. Subunit IB (117.2–125.9 mbsf, Hole 1196A; 122.9–130.5 mbsf, Hole 1196B) is a pale brown dolomitized floatstone-rudstone with predominantly elongated fragments of branching red algae in a recrystallized grainstone matrix. Subordinate rudite-sized components are molds of large hyaline benthic foraminifers, mollusks, and bryozoans. The lower boundary of Subunit IB consists of a sharp lithologic change.
7. Subunit IA (0–117.2 mbsf, Hole 1196A; 0–122.9 mbsf, Hole 1196B) is a white to pale brown (or yellow) dolomitic floatstone-rudstone with abundant rhodoliths as large as 10 cm in a grainstone matrix. Its subordinate rudite-sized components are lamellar coral colonies, molds of large hyaline benthic foraminifers, mollusks, and bryozoans. These bioclasts, together with red algae fragments, represent a moderately sorted and fine to medium sand matrix. Mud is only present as discontinuous laminae as thin as a few millimeters. A crude stratification with a fining upward trend is sometimes defined by small rhodolith layers. Corals become common upcore in the uppermost five cores, with either colonial secondary reef frame builders or solitary forms (Table T1). In Hole 1196A, the top of Subunit IA has an irregularly iron-stained surface. This surface is capped by a 1-cm-thick layer of wackestone with a planktonic foraminiferal assemblage of Pliocene age (Shipboard Scientific Party, 2002a).

The vertical succession at Site 1199 (Hole 1199A) is partly similar to those described at Site 1196. It comprises six subunits (Fig. F5).

Subunit IIB (285.0–410.0 mbsf) is a thick succession of white to pale yellow (dolomitic) limestone. It consists of meter-scale alternations of floatstones with rhodoliths as large as a few centimeters and well-sorted medium to coarse sand-sized grainstones. The biogenic components encountered include red algae fragments, hyaline larger benthic foraminifers, bivalves, gastropods, echinoid spines, and bryozoans. Coral fragments are present at the top of Subunit IIB in Core 194-1199A-39R. Its lower boundary corresponds to a gradual lithologic change to a 5-cm-thick white sucrosic dolostone. This facies was retrieved by the core catcher of the lowermost core (194-1199A-45R) from Hole 1199A. Subunit IIB facies and the underlying sucrosic dolostone facies are very close to Subunits IIIA and IIIB facies from Hole 1196A, respectively.

Subunit IIA (159.8–285 mbsf) from Site 1199 is very similar to Subunit IIA from Site 1196. Its upper part consists of a pale brown, slightly dolomitized floatstone with large porcellaneous foraminifers, mollusks, solitary corals, and bryozoans in a silt-sized grainstone matrix. Its lower part also contains a noticeable amount of coral fragments of possible secondary reef frame builders (Table T1).

Subunit ID (121.9–159.8 mbsf) is a very pale brown to white dolomitic floatstone with a grainstone matrix. Biogenic components consist of a variable amount of elongated fragments of branching red algae, rhodoliths with associated bryozoans, and large hyaline benthic foraminifers as molds. Corals are locally present as branching colonies within rudstone layers. The top of Subunit ID corresponds to a 3-cm-thick red micritic layer rich in silt-sized quartz grains (Shipboard Scientific Party, 2002b).

Subunit IC (114.1–121.9 mbsf) is a very pale brown to light reddish dolomitized floatstone-rudstone and boundstone. The rocks are locally leached and infiltrated by reddish silt (Shipboard Scientific Party, 2002b). Biogenic components are fragments of branching red algae, molds of large hyaline benthic foraminifers, and massive and branching coral and rare rhodoliths as large as a few centimeters.

The last two subunits from Site 1199, IB (106.6–114.1 mbsf) and IA (0–106.6 mbsf), exhibit the same facies and thicknesses as Subunits IB and IA from Site 1196, respectively. Subunit IB is also a pale brown dolomitized floatstone with branching red algae in a recrystallized grainstone matrix. The only difference is the occurrence of rare corals. The lower boundary of Subunit IIB corresponds to a sharp lithologic change. Subunit IA is a white to pale brown (yellow) dolomitic floatstone-rudstone with centimeter-sized rhodoliths in a grainstone matrix. An increasing amount of coral upcore is also observed in the five uppermost cores. The coral assemblages are given in Table T1.