Site 1130 is located at a water depth of 488.0 m on the upper slope of the eastern Eyre Terrace. The objective at this site was to intersect the thick Pleistocene carbonate succession and the distal parts of the Paleo-cene-Eocene? progradational siliciclastic wedge in an upper slope depositional setting. Four major sedimentary units were recognized and subdivided (Fig. F3) on the basis of major sediment type, texture, composition, color change, presence of firmgrounds, and soft sediment deformation. The lowest package consists of calcareous sandstone of presumed Eocene age that was probably deposited in a marginal marine setting. The overlying, poorly recovered interval consists of chert (silicified nannofossil planktonic foraminiferal ooze) intervals. The third sedimentary unit is dominated by pelagic calcareous ooze and chalk. The shallowest and thickest unit is characterized by a repetitive succession of bioclastic packstones, punctuated by bioclastic wackestone layers and occasional calcareous ooze to chalk intervals.
Recovery was more than 95% within the upper 329 mbsf of the cored interval but then dropped abruptly because of the presence of soft calcareous chalks and interbedded hard chert layers. Unit boundaries in these low recovery intervals are defined by first and last occurrence (FO and LO, respectively) of particular lithologies (e.g., silicified planktonic foraminiferal ooze or calcareous sandstone)
Unit I consists of light gray to pale olive, strongly bioturbated, unlithified bioclastic packstone punctuated by intervals of unlithified bioclastic wackestone and nannofossil ooze. Unit I is divided into three subunits on the basis of different sedimentation patterns, textural changes, and the presence of hardgrounds and nannofossil ooze intervals (Fig. F3). Subunits IA and IB are characterized by a repetitive succession of uniform bioclastic packstones in the upper part punctuated by bioclastic wackestone layers in the lower part. The two subunits are separated by a distinct calcareous ooze interval. Subunit IC is dominated by bioclastic packstones, with a slump at its base.
Subunit IA consists of a succession of massive, uniform bioclastic packstone in the upper part and alternating layers of wackestone to packstone in the lower part. The lowermost bed in Subunit IA is a nannofossil ooze.
The matrix of the unlithified packstones is dominated by calcareous nannofossils, abundant bioclasts, benthic and planktonic foraminifers, sponge spicules, and tunicate spines. The sand-sized fraction (>63 µm) contains varying amounts of bioclasts and planktonic foraminifers and common to abundant benthic foraminifers and sponge spicules. Echinoid and tunicate spines are present. The silt- to sand-sized unlithified bioclastic packstones have subtle but distinct color alternations ranging from light olive gray to light gray. Generally, the lighter layers are finer grained and planktonic foraminifer rich, whereas the darker layers are coarser grained and contain more bioclasts. The sediments are moderately to strongly bioturbated.
Deposits between 67.7 and 99.73 mbsf are characterized by the presence of scattered soft lumps of nannofossil ooze. These white unlithified clasts "float" in the wackestone or packstone matrix, and they appear out of context with respect to the major lithology.
Below 78 mbsf, the sediment pattern changes to alternating layers of unlithified wackestone and packstone. The generally light gray, very fine grained wackestones are compositionally and texturally similar to nannofossil ooze. The wackestone matrix is mostly calcareous nannofossils, common benthic foraminifers, sponge spicules, bioclasts, and tunicate spines. Echinoid spines and planktonic foraminifers are present. The wackestone coarse fraction (>63 µm) is dominated by bioclasts, common planktonic and benthic foraminifers, and sponge spicules. There are rare bryozoans and traces of dark brown grains, quartz, tunicate spines, bivalves, and ostracodes. The wackestones contain a greater proportion of nannofossils, sponge spicules, and tunicate spines than the packstones. The deposits are moderately bioturbated, as shown by color mottling. Interval 182-1130B-11H-5, 0-113 cm, in particular, contains a large Thalassinoides network.
The lower boundary of Subunit IA is at the base of a white nannofossil ooze with bioclasts. The ooze contains well-defined burrows that are usually stiffer and better lithified than the surrounding sediment, with deep Thalassinoides burrowing present in interval 182-1130B-15H-1, 127-150 cm.
The boundary between Subunits IA and IB is a sharp contact between the upper thin but distinct layer of white to light gray nannofossil ooze and the lower light olive-gray, very fine grained bioclastic packstone.
The sedimentary pattern in Subunit IB is similar in style to the succession in Subunit IA, with the main difference being the lack of firmgrounds. The uppermost part of the subunit is composed of uniform unlithified packstone with a few wackestone interbeds in the lower part.
The unlithified bioclastic packstones of Subunit IB are characterized by alternating light olive-gray and pale olive color changes. Grain size ranges from silt to fine sand, but the unlithified packstones in the lower part of the subunit are generally finer grained and contain more mud. Components of the >63-µm fraction are planktonic foraminifers, benthic foraminifers, sponge spicules, blackened grains, and glauconite grains. The matrix is dominantly calcareous nannofossils, abundant bioclasts, common planktonic foraminifers, and sponge spicules.
The sediments are moderately to strongly bioturbated and change from unlithified to partially lithified in a transition zone between 170 and 180 mbsf. The gray, fine-grained, unlithified rudstone bed that grades upward into a light gray bioclastic floatstone and then into a bioclastic packstone at ~187-188 mbsf is interpreted as a turbidite. It contains pebble-sized bryozoan fragments (vagrant and delicate branching growth forms), granule-sized shell fragments, an azooxanthellate coral, and benthic foraminifers. The deposit has a sharp erosional base, whereas the contact with the overlying bioclastic packstone lithology is transitional due to bioturbation.
In the lower part of Subunit IB, below 200 mbsf, the deposits are alternating layers of bioclastic wackestone and packstone, with a thin bed of nannofossil ooze overlying a firmground at the base. The matrix in grain-supported intervals is dominantly calcareous nannoplankton, abundant to common bioclasts, with minor planktonic and benthic foraminifers and sponge spicules (see "Site 1130 Smear Slides"). The coarse fraction is mostly bioclasts. Lighter layers contain abundant planktonic foraminifers, whereas darker layers are rich in blackened grains and glauconite. Benthic foraminifers, sponge spicules, and echinoid spines are also present.
The fine-grained wackestones in the lower part of the subunit are light gray to light olive gray in color, with gradational changes between colors. The wackestone matrix is dominated by calcareous nannofossils, abundant bioclasts, varying amounts of benthic and planktonic foraminifers, common tunicate spines, and sponge spicules. There are traces of quartz and pyrite grains. The coarse fraction has the same composition as the packstones, but with large numbers of planktonic and benthic foraminifers.
Both packstones and wackestones are strongly bioturbated throughout, which is shown as color mottling. Thalassinoides and Chondrites burrows of the uppermost parts of burrows are best shown in transition zones from darker grain-supported to lighter mud-supported intervals. Shell fragments, bivalve fragments, gastropods, and benthic foraminifers are scattered throughout.
A turbidite with pebble-sized gray bryozoan debris, blackened grains, and echinoid spines is present at 229.37-229.80 mbsf. It is characterized by inverse to normal grading and is poorly sorted (Fig. F4). The boundary between Subunits IB and IC is defined by a hardground and facies change.
The upper boundary of Subunit IC is marked by the presence of a firmground and a change in lithology; the lower boundary is placed at the base of a bed characterized by synsedimentary deformation and interpreted as a slump.
The bioclastic packstone is characterized by color alternation ranging from olive to light gray. The matrix of the packstones is dominated by calcareous nannofossils, with varying amounts of bioclasts and benthic and planktonic foraminifers. The sediment also contains sponge spicules, tunicate spines, diatoms, ostracodes, and dolomite (see "Site 1130 Smear Slides").
The components of the >63-µm fraction are fine-grained abundant to dominant bioclasts, abundant to common benthic and planktonic foraminifers, and minor amounts of blackened grains, glauconite, echinoid spines, sponge spicules, tunicates, and ostracodes. Lighter layers contain more planktonic foraminifers, whereas darker layers are richer in blackened grains. The deposits are moderately to strongly bioturbated and partially lithified. The slump at the base of the Subunit IC (Fig. F5) consists of alternating layers of glauconitic bioclastic packstone and white nannofossil bioclastic packstone, suggesting entrainment of the underlying lithology.
Lithologies in Unit II are calcareous nannofossil foraminiferal chalk and ooze, punctuated by two grainstone to floatstone intervals in the lower part. Texturally, these sediments range from mudstone to packstone, and lithification varies from unlithified to partially lithified (Fig. F3), resulting in alternating layers of soft oozes and harder chalks. The matrix is dominated by calcareous nannofossils, common planktonic foraminifers, and some bioclasts. Components of the >63-µm fraction are abundant planktonic foraminifers, some benthic foraminifers, and few bioclasts. Glauconite and blackened grains are scattered throughout the unit and are common in the lower part. The sediments are moderately to strongly bioturbated, which is manifested by color mottling.
The deposits in the lower 30 m of Unit II are characterized by firmgrounds, two grainstone beds, and thin, alternating wackestone-packstone layers punctuated by omission surfaces. The upper grainstone bed (intervals 182-1130A-34X-1, 46-51 cm, and 182-1130C-2R-4, 123-126 cm) is a light olive-gray, partially lithified, fine sand-sized planktonic foraminiferal grainstone that texturally grades upward to a grainstone to packstone with a sharp base and gradational bioturbated top. In addition to the planktonic foraminifers, some of which are filled with glauconite, it also contains benthic foraminifers, well-cemented packstone to grainstone clasts, bivalve fragments, sponge spicules, ovoid fine- to medium-sized brown bioclasts (limonite?), and minor amounts of pyrite. The grain size is fine sand. In Hole 1130C, the underlying nannofossil foraminiferal chalk underwent some minor synsedimentary deformation (slump).
The lower grainstone bed (intervals 182-1130A-34X-4, 59-76 cm, and 182-1130C-3R, 56-59 cm) is a fine to medium sand-sized bioclastic grainstone (Hole 1130A) containing skeletal fragments, glauconite, planktonic foraminifers, benthic foraminifers, bryozoans, and bivalve fragments. Both upper and lower contacts are sharp. The equivalent layer in Hole 1130B is a partially lithified floatstone with bioclasts and planktonic foraminifers. The upper contact is sharp, whereas the lower one was not recovered. Both intervals are interpreted as turbidites. Omission surfaces and firmgrounds were recognized in Hole 1130C only. This is probably the result of different drilling techniques (XCB vs. RCB), with frequent biscuiting observed in XCB cores.
This unit was poorly recovered. The only sediments recovered were fragments of silicified nannofossil foraminiferal chalk, some of which are draped with a thin layer of unlithified nannofossil ooze to partially lithified chalk. A reasonable inference is that the entire unit consists of ooze and that beds or lenses of preferentially silicified nannofossil foraminiferal ooze were the only materials recovered. Unit boundaries were defined by the FO and LO of silicified nannofossil foraminiferal chalk. The lithified white to very dark gray, silicified nannofossil planktonic foraminiferal ooze (chert/porcellanite) has a wackestone to packstone texture and a grain size ranging from very fine sand to silt. Major components are large to small benthic foraminifers, very small planktonic foraminifers, and blackened grains. The matrix is dominated by calcareous nannofossils, but it also contains planktonic and benthic foraminifers, bioclasts, and sponge spicules. Most fragments have burrows filled with white, fine to very fine grained nannofossil foraminiferal chalk, ranging from packstone to grainstone in texture. No macrofossils were recorded in Unit III.
The upper boundary of the unit was defined by the first occurrence (FO) of calcareous sandstone in Core 182-1130C-8R. Overall recovery was poor, and sediments were biscuited or fragmented during drilling.
Four lithologies were recovered in this interval: (1) calcareous sandstone, (2) bioclastic glauconitic wackestone, (3) bryozoan grainstone, and (4) bivalve grainstone (see "Site 1130 Thin Sections").
The red calcareous sandstone is poorly sorted. The grain distribution is bimodal with fine sand- to granule-sized grains within a carbonate bioclastic wackestone to packstone matrix. Terrigenous components consist of sand-sized, subrounded iron-coated grains, quartz, feldspar, opaque minerals, and glauconite. Carbonate components are bryozoans, benthic foraminifers, minor bioclasts, and a piece of azooxanthellate coral, all of which are filled with light brown carbonate mud.
Thin-section analysis (Sample 182-1130B-40X-1, 5-6 cm) shows that the red to orange sediment varies from a calcareous sandstone to a sandy limestone and is distinguished by very coarse to sand-sized grains and pink to orange carbonate. Texturally, the sediment is a packstone to wackestone. The composition of the terrigenous clastic components is bimodal, comprising very coarse subrounded quartz and feldspar particles and fine, more subrounded to angular quartz grains. The feldspar is altered to clay along cleavage planes. Both polycrystalline and single-crystal quartz grains are present. Most of the grains are iron coated, and some are cemented together by limonite?. Small fractures within the grains are also zones of Fe oxide precipitation. Fine sand-sized glauconite is present, and the periphery of many glauconite particles are altered to limonite. Fine sand-sized ovoid limonite/goethite grains typically have an oolitic texture; in some instances, small angular quartz grains are also coated with layers of limonite.
Carbonate components are dominated by bryozoan and echinoid grains with lesser benthic foraminifers. Echinoid remains consist of spines and plates, whereas the bryozoans are fragmented and composed of delicate, articulated, and flat robust branching forms. Benthic foraminifers are miliolids, amphisteginids?, textularids, and some encrusting growth forms. Other grains include brachiopod and ostracode fragments. Many particles are also sites of Fe oxide precipitation, especially in microborings and echinoderm stoma. The fine-grained, mud-sized matrix is entirely microbioclastic carbonate, containing some planktonic foraminifers. Fe oxides are also present throughout the matrix.
Diagenesis is visible in a few minor spar-filled molds, but positive identification of origin is difficult. Overall, there is little obvious neomorphism, but fuzzy grain boundaries suggest minor crystal enlargement.
The red bioclastic glauconitic wackestone (or bioclastic wackestone with glauconite) contains varying amounts of fine to very fine sand-sized glauconite, coarse- to fine-grained bioclasts, echinoid spines, bryozoans, and other unidentifiable particles. Some fragments show grading from glauconite-poor to glauconite-rich intervals, and some possible cross lamination. One fragment at interval 182-1130C-8R-1, 82-85 cm, contains a fine gray carbonate mudstone to very fine grained carbonate siltstone layer.
The medium to very coarse grained bryozoan grainstone is white to light red. Its diverse bryozoan assemblage ranges from mainly articulate to fenestrate and flat robust branching bryozoans. It also contains abundant angular to rounded and moderately sorted quartz grains and common bioclasts. Serpulid worm tubes, gastropods, bivalves, echinoid spines, and opaque grains are present.
The bivalve grainstone is very coarse grained and pink in color. It contains abundant bivalve fragments and quartz. Articulate and delicate branching bryozoans and serpulid worm tubes are common. The components are subangular to rounded and well sorted.
The basal calcareous sandstones at Site 1130 (Unit IV) were poorly recovered and thus provide little information about the development of the succession (Fig. F3). However, both the bryozoan assemblage and benthic foraminifer assemblage (see "Biostratigraphy") suggest a shelf environment. Further marine indicators are benthic foraminifers in the matrix, carbonate mud indicating a quiet-water depositional environment, and bioturbation. The calcareous sandstones are barren of datable microfauna (see "Biostratigraphy"), but tentative correlation with a succession drilled in Jerboa 1 (Bein and Taylor, 1981) suggests an Eocene age. Unit IV is equivalent to the top part of the seismic Sequence 7 (Feary and James, 1998, reprinted as Chap. 2; see "Seismic Stratigraphy").
A dramatic change of sedimentation style from shelf-dominated Eocene calcareous sandstones to pelagic Oligocene-lower Pliocene sediments (Units III and II) occurs at 366.40 mbsf. The boundary was not recovered; very poor recovery in the silicified nannofossil planktonic foraminiferal ooze (chert) beds of Unit III prevents further interpretation of the development of the depositional realm. The abrupt change from silicified nannofossil planktonic foraminiferal ooze to partially lithified nannofossil ooze coincides with a hiatus of 15 m.y. (see "Biostratigraphy") and with the top of seismic Sequence 6A (see "Seismic Stratigraphy"). The well-recovered Unit II is a succession of chalk and ooze in which the lower part is characterized by discontinuous sedimentation, represented by firmgrounds or omission surfaces and by redeposition of sediment shed from the shelf in the form of turbidites. The upper part of Unit II is uniform upper Miocene-lower Pliocene nannofossil chalk and ooze and is represented by seismic Sequence 3.
The boundary to Unit I is an abrupt change in depositional style at the base of a slump (Fig. F5), from pelagic deposition to shelf-dominated deposition of bioclastic packstones. This coincides with a 2-m.y. hiatus recognized in the microfauna (see "Biostratigraphy"), an abrupt decrease in natural gamma radiation (NGR) (see "Physical Properties"), and the disappearance of aragonite (see "Inorganic Geochemistry").
The upper Pliocene bioclastic packstones of Subunit IC record variations in input of shelf-derived material, with intervals containing blackened and glauconitic grains alternating with mud-supported intervals rich in planktonic foraminifers. The boundary between Subunits IC and IB coincides with the Pliocene/Pleistocene boundary and coincides with the base of Sequence 2, a regional unconformity (see "Seismic Stratigraphy").
Subunits IA and IB span the lower-upper Pleistocene and were deposited as sigmoidal clinoforms (see "Seismic Stratigraphy"). The sedimentary record indicates that these clinoforms can be divided into two depositional packages separated by a flooding interval consisting of nannofossil ooze. This interval corresponds to a prominent reflector within seismic Sequence 2 in the seismic line, separating lower from upper Pleistocene sediments. The lower parts of Subunits IA and IB consist of alternating wackestone and packstone layers, with occasional turbidites (Fig. F4) representing the bottomset style of clinoform sedimentation, whereas uniform bioclastic packstone represents the topset style.