A minor amount of sediments, sedimentary rocks, and lithoclasts was recovered at Sites 1110, 1111, and 1112. No sediment was recovered at Site 1113. The different sediment types are recognized on the basis of sediment or rock type, grain size, sedimentary structures, color, compositions determined in smear slide and thin sections, bulk mineralogy (X-ray diffraction [XRD]), and calcium carbonate determinations. Details of the sediments are given first, followed by a brief interpretation, in the order of Site 1110, Site 1111, and then Site 1112. The very low recovery did not warrant presentation of lithologic logs as given for the other sites drilled during Leg 180. In addition, much of the recovery from Sites 1110, 1111, 1112, and 1113 consisted of angular fragments of igneous and metamorphic rocks interpreted as talus (see "Igneous and Metamorphic Petrology").
Quaternary, mainly fine-grained sediments, together with minor amounts of coarser grained sediment and isolated clasts of metamorphic and minor igneous rock, were recovered at Site 1110. The sediments are described below, whereas the metamorphic clasts are described separately (see also "Igneous and Metamorphic Petrology").
The uppermost few meters at Site 1110 were cored in Holes 180-1110A and 1110B. These two cores include a number of distinctive marker horizons, notably an individual very thin volcanic ash bed (~2 cm thick), siliciclastic sands, and greenish silt layers, which together allow a precise correlation between the three holes (Fig. F1; see also "Composite Depths"), confirming that a complete succession was recovered.
The sedimentary lithologies recovered are described below.
Gray and olive gray, clay-rich nannofossil ooze and foraminiferal ooze dominate the upper part of the recovery in Cores 180-1110A-1H and 2H. In Core 180-1110B-1H, calcium-carbonate analyses indicate values from 27 to 41 wt% (see "Organic Geochemistry").
Very thin beds (<3 cm) of nannofossil-rich ooze exhibit sharp bases, normal grading, and diffuse tops (e.g., Fig. F2). Sulfide mottling is observed in places. Beneath this, Core 180-1110A-2H contains numerous structureless beds of greenish gray nannofossil ooze, up to several tens of centimeters thick (see also description of Section 180-1110B-1H-CC in "Calcareous Nannofossils").
In smear slides ("Site 1110 Smear Slides") the nannofossil ooze contains nannofossils, quartz, feldspar, biotite, accessory minerals, biogenic and inorganic calcite, together with planktonic foraminifers, radiolarians, and sponge spicules. Volcanic glass is seen in some, but not all samples. Also, radiolarians are sporadic. The XRD analysis of silty nannofossil clay indicates the presence of quartz, calcite, plagioclase, chlorite, amphibole, and illite (see Table T6).
Silty clay, with or without abundant nannofossils, is present in Cores 180-1110A-1H and 2H. This lithology exists as four subtle color variants (i.e., greenish gray, dark gray, dark olive gray, and olive). Silty clay also predominates in Core 180-1110B-2X, where it contains numerous small shell fragments. One XRD analysis revealed the presence of calcite, quartz, chlorite, plagioclase, and amphibole (see Table T6). The calcium carbonate contents of samples from Core 180-1110A-2H are 9.2-35.4 wt%.
A thin bed of normal-graded volcaniclastic silt is present in interval 180-1110A-2H-1, 25-26 cm. Silt recovered in Section 180-1110A-1H-5 is volcaniclastic, with >70% colorless glass shards. In smear slides, the silt contains similar components as the fine-grained sand, described below, with the addition of clay, rare chloritic or glauconitic grains ("Site 1110 Smear Slides").
Very thin beds of normal-graded sandstone (<2.5 cm thick) were rarely recovered. Blue gray sand of siliciclastic origin was observed in Core 180-1110A-1H as a minor lithology. Compositionally, as seen in smear slides ("Site 1110 Smear Slides"), the sand is dominated by metamorphic lithoclasts and planktonic foraminifers. In addition, quartz, plagioclase, mica, epidote, shell fragments, biotite, muscovite, rare igneous rock fragments, accessory minerals, biogenic and inorganic calcite, coccoliths, and sponge spicules are present. The XRD analysis confirmed the presence of chlorite and illite as the clay minerals present, in addition to quartz, plagioclase, and amphibole (Table T6).
Gravel, mainly composed of metamorphic rock fragments (up to 1.8 cm in size), is present in Sections 180-1110A-2H-2 and 2H-CC. A single bed, graded from granules to coarse grains, then medium- and fine-grained sand, is present from 0 to 50 cm in Section 180-1110A-2H-2 (Fig. F3). Individual clasts are greenschist mylonite and pelitic schist with additional rare clasts of granite. Similar gravel is seen in Core 180-1110B-3X.
A thin volcanic ash bed was identified in interval 180-1110B-1H-3, 51-53 cm. In addition, volcanic glass is widely disseminated throughout other sediment types.
A number of isolated metamorphic clasts and rare igneous rocks were recovered in Cores 180-1110B-3X and 180-1110D-1W and 2R. These are mostly angular and up to 5 cm in size, although their size is probably an artifact of drilling. Clast types included epidosites, greenschist metapelite, greenschist mylonite, and microgranite (see "Igneous and Metamorphic Petrology".
Based on paleontological evidence, the fine-grained sediments recovered from Site 1110 accumulated in deep water (see "Biostratigraphy"). The background sediment is represented by nannofossil- and foraminifer-rich ooze and clay, with a minor contribution from siliceous micro-organisms (radiolarians and sponge spicules). Rare thin beds consisting almost entirely of glass are interpreted as pyroclastic air-fall tuff. More commonly, volcanic glass is reworked through other lithologies.
Three types of gravity-flow deposits are recognized: (1) very thin, normal-graded beds of clay and silty clay, composed of mixed siliciclastic-derived sediments and volcanic ash. These are interpreted as hemipelagic sediment that was redeposited by low-density turbidity currents; (2) thin beds of graded sand composed of siliciclastic (metamorphic) grains and planktonic foraminifers, also interpreted as turbidity current deposits; and (3) granule conglomerate grading into sand, composed of metamorphic detritus and interpreted as high-density turbidity current deposits.
In addition, isolated angular clasts, as long as 7 cm, were recovered. These are mainly composed of green-colored schist of probable greenschist metamorphic grade, dark pelitic schist, and altered, but undeformed, granitic rock. The clasts were probably derived from mass-flow deposits.
In summary, Site 1110 records deep-water Quaternary sedimentation in a setting of extreme sediment instability, as shown by the abundance of turbidites and inferred mass-flow deposits. Metamorphic clasts are most likely to be talus deposits derived from the nearby Moresby Seamount.
There was limited recovery of sediments and individual clasts of igneous, metamorphic, and rare sedimentary rocks at Site 1111.
There was no recovery from the seafloor to 10.1 mbsf (represented by Core 1R), and thereafter only minimal recovery in Cores 2R, 3R, 4R, 6R to 8R, 10R to 18R, and no recovery at all in Cores 5R and 9R. The hole reached 173 mbsf. Most of the material recovered consisted of clasts of metamorphic rock and minimal recovery of fine-, medium-, and coarse-grained sediment. Only in Core 8R was there any more substantial recovery.
The lithologies recovered are described below.
Nannofossil-bearing clay was recovered in Core 2R. The clay is green, massive, and contains planktonic foraminifers, sponge spicules, and calcareous fragments. Silty nannofossil clay and ooze were found, based on XRD analysis, to consist of plagioclase, quartz, calcite, chlorite, illite, and smectite(?) (Table T6).
Very minor greenish gray calcareous clay with pebbles of epidote schist was recovered in Core 3R. Very minor, greenish brown clay with lamprophyre was recovered, in addition to discrete clasts of lamprophyre in Core 4R. The XRD data indicate that the calcareous clay contains only calcite and aragonite, whereas the silty clay additionally contains plagioclase and chlorite (Table T6).
Dark greenish gray nannofossil-rich silty clay was recovered in Sections 8R-1 through 8R-3 and 8R-CC. A smear slide of the silty clay was found to contain quartz, feldspar, muscovite, clear volcanic glass, epidote, biogenic and inorganic carbonate grains, planktonic foraminifers, radiolarians, coccoliths, sponge spicules, and rare fine plant material ("Site 1110 Smear Slides").
Very minor nannofossil-rich silt was recovered in Core 6R, together with fragments of dolerite and metadolerite.
Very minor dark greenish gray silt and fine-grained sand were recovered in Core 7R. A small amount of dark greenish, coarse-grained sand was also observed, together with angular to subangular fragments of phyllite and gabbro. Blue gray, normal-graded, coarse- to fine-grained sand is present in interval 180-1111A-8R-1, 69.5-53.5 cm. In addition, a very thin bed of volcaniclastic sand is present in interval 180-1111A-8R-2, 124-125 cm.
A smear slide of fine-grained sand contains abundant metamorphic rock fragments, quartz, feldspar, muscovite, inorganic calcite, foraminifers, nannofossils, and sponge spicules, together with common pyrite, in both amorphous form and as isolated cubes ("Site 1111 Smear Slides").
The Pleistocene sediments recovered at Site 1111 record similar depositional processes to those at Site 1110 (see "Site 1110"), as far as can be determined from the minimal recovery. The succession is inferred to contain abundant talus of mainly metamorphic rocks, intercalated with clay and silty clay, silt, and sand. Some of the sediments may also represent matrix to the talus. The sediment is mainly disturbed, and very few sedimentary structures indicative of a depositional process are preserved. Those that exist again suggest deposition by turbidity currents. In addition, the talus is interpreted as the product of mass flows derived from the adjacent margin of the Moresby Seamount.
At Site 1112 there was also only limited recovery of sediments including individual clasts of igneous, metamorphic, and rare sedimentary rocks. Minimal recovery from Cores 1R and 2R (0-20.5 mbsf) revealed nannofossil-rich silty clay with rare laminae and thin beds of coarse-grained siliciclastic sandstone. In the latter core, two thin beds of volcanic ash were observed. Cores 3R through 13R consist mainly of metamorphic rocks (greenschist metadolerite) and volcaniclastic sandstone with some silty claystone. The results of smear-slide analysis of the sediments and sedimentary rocks recovered from this site are described below and in "Site 1112 Smear Slides".
Five smear slides were studied, which showed these sediments to be composed of grains of quartz, feldspar, biotite, rare basaltic and metamorphic rock fragments, clear volcanic glass, inorganic calcite, abundant coccoliths, planktonic foraminifers, rare siliceous sponge spicules, rare diatoms, and rare radiolarians.
Smear-slide analysis of the two beds of volcanic ash (silt clay) showed the higher of these (light gray) to be dominated by brown glass shards, whereas the lower (dark gray) was dominated by colorless glass shards.
Two thin sections of the volcaniclastic sandstones were studied: (1) a coarse-grained volcaniclastic sandstone (Sample 180-1112A-9R-CC, 25-27 cm) consisting of abundant rounded to subrounded volcanic lithoclasts of mafic (basaltic and andesitic) and acidic origin (rhyolitic and dacitic), and minor devitrified glass (vitric) (Figs. F4, F5; "Site 1110 Thin Sections, Site 1111 Thin Sections, Site 1112 Thin Sections, Site 1113 Thin Sections"). Also present are angular detrital grains of plagioclase, feldspar, biotite (chloritized), hornblende, and clinopyroxene; and (2) a medium-grained volcaniclastic sandstone (Sample 180-1112A-3R-1, 2-5 cm) composed of abundant rounded to subrounded lithoclasts of basaltic and andesitic fragments and angular detrital grains of plagioclase, feldspar, quartz, biotite, hornblende, and clinopyroxene (Fig. F6).
Examination of a single thin section of silty claystone (Sample 180-1112A-6R-1, 10-12 cm) showed this to be composed of detrital grains of feldspar, biotite, quartz, clinopyroxene, opaque minerals, and minor carbonaceous detritus set in a claystone matrix ("Site 1110 Thin Sections, Site 1111 Thin Sections, Site 1112 Thin Sections, Site 1113 Thin Sections").
The Pleistocene sediments recovered at Site 1112 record similar depositional processes to those at Sites 1110 and 1111 (see "Site 1110" and "Site 1111"), as far as can be determined from the minimal recovery. The succession is inferred to contain abundant talus of mainly metamorphic rocks, intercalated with clay and silty clay, silt, and sand. The sediment is mainly disturbed, and very few sedimentary structures indicative of depositional process are preserved. Those that exist, again suggest deposition by turbidity currents. Of the two ash layers recovered, the clear volcanic glass is thought to represent an ash fallout whereas the brown basaltic glass is probably of submarine origin related to spreading of the Woodlark Basin.