Quantitative parameters of Pleistocene pelagic sedimentation in the Atlantic Ocean

Lithological–facies maps of Eopleistocene and Neopleistocene sediments (with 10 and 20 m isopachs) are compiled for the pelagic part of the Atlantic Ocean based on materials recovered by 283 ocean drilling sites. Data for both maps were calculated using A.B. Ronov’s volumetric method. The calculated results include such quantitative sedimentation parameters of major sediment types as the areas covered by these sediments, their volumes, masses of the dry sedimentary material, and masses of sedimentary material deposited per specified time unit. These parameters are compared for both Eopleistocene and Neopleistocene time, and the data are utilized to separately interpret the results for terrigenous, carbonate, and siliceous sediments. The supply of terrigenous material is proved to have been enhanced in the Pleistocene as a result of both tectonic uplift of continents and climatic changes, including intensification of continental glaciation at high latitudes in both hemispheres. The growth in the productivity of carbonate plankton was overridden by growing generation of bottom and deep water masses and ensuing intensification of the dissolution of pelagic carbonates. The productivity of siliceous plankton practically did not change, perhaps, because of a favorable combination of the supply of dissolved silica and other nutrients from both West and East Antarctica.     

Quantitative parameters of pleistocene pelagic sedimentation in the Pacific Ocean

Using the methodology of A.B. Ronov, we compiled lithofacies maps for the Early and Middle-Late Pleistocene pelagic sedimentation of the Pacific Ocean, accounting for sediment thicknesses. We calculated areas, volumes, masses, and accumulation rates of main sediment types for both Pleistocene subdivisions. A comparison of the results confirmed a strong increase in the rates of terrigenous and biogenic sedimentation. Special emphasis was laid on intensification of sea-ice and eolian sedimentation for the terrigenous types of sediments and on the evolution of siliceous and carbonate sedimentation for the biogenic types of sediments.     

Facies structure and quantitative parameters of pleistocene pelagic sedimentation in the Indian Ocean

We compiled lithofacies maps for the early and middle-late Pleistocene (Eopleistocene and Neopleistocene, respectively) pelagic sedimentation of the Indian Ocean and a database for sediment thicknesses in the respective stratigraphic subdivisions. Using these data, we calculated areas, volumes, masses, and intensities of accumulation of main sediment types for both Pleistocene subdivisions. A comparison of the results confirmed a strong increase in the rate of terrigenous sedimentation. Special attention was given to the evolution of siliceous and carbonate sedimentation of the biogenic type.     

Facies Structure and Quantitative Parameters of Pleistocene Sediments of the Bering Sea

Lithofacies zoning is described for the first time for the Neo- and Eopleistocene of the Bering Sea. Four lithofacies sedimentation zones are distinguished: (I) terrigenous; (II) siliceous–terrigenous; (III) siliceous, and (IV) volcanoterrigenous ones. Corresponding maps were treated using Ronov volumetric method to quantify sedimentation parameters for distinguished lithofacies zones (subzones) and types of Pleistocene sediments. It was revealed that terrigenous sediments predominate over other sediments. Accumulation of the terrigenous sediments was more intense (by 1.4 times) in the Neopleistocene than in the Eopleistocene. The sedimentation rate of siliceous sediments of the Bowers Ridge in the Eopleistocene was two times higher than in the Neopleistocene.     

Sedimentation rates in the Late Cretaceous epicontinental basin in the south of the Russian Plate

This paper discusses integrated analysis of sedimentation rates of Late Cretaceous sediments in the south of the Russian Plate. The first map of Late Cretaceous sedimentation rates in this region has been constructed using equal-rate contours; the rates were calculated for ages and epochs at 38 reference sites based on a chronostratigraphic scale and published data and for biostratigraphic zones at 5 sites. The sedimentation rates of pelagic carbonate and siliceous sediments in the Late Cretaceous basin of the Russian Plate ranged from 0.1 to 1 n cm/1000 years with a maximum of 2–3 cm/ka in the Caspian Syneclise. The predominantly terrigenous and siliceous-terrigenous sediments could accumulate in the south of the Ulyanovsk-Saratov basin at a rate of 1–3 m/ka.     

孟加拉湾东经90°海岭中上新世以来沉积记录及亚洲季风

利用古生物地层学、碳酸盐地层学、X射线粉晶衍射和粒度分析等方法对东北印度洋孟加拉湾东经90°海岭上的远洋沉积物进行了综合研究.在此基础上, 以陆源物质的粒度为切入点对该区的沉积作用、沉积物来源及其可能的搬运机制进行了探讨, 对过去有关研究区陆源物质的源区和搬运方式作了补充.陆源物质的粒度可作为东南季风或赤道东风的替代性指标, 其变化不仅反映源区的火山活动情况, 而且指示了风力的强弱.陆源物质的多少则主要取决于青藏高原和印度次大陆的剥蚀情况和地表径流的强弱.二者之间通过高原隆升及其引发的环境效应联系起来.      

Distribution and tectonic implications of Cretaceous-Quaternary sedimentary facies in Solomon Islands

Sedimentary rocks of the Solomon Islands-Bougainville Arc are described in terms of nine widespread facies. Four facies associations are recognised by grouping facies which developed in broadly similar sedimentary environments.A marine pelagic association of Early Cretaceous to Miocene rocks comprises three facies. Facies Al: Early Cretaceous siliceous mudstone, found only on Malaita, is interpreted as deep marine siliceous ooze. Facies A2: Early Cretaceous to Eocene limestone with chert, overlies the siliceous mudstone facies, and is widespread in the central and eastern Solomons. It represents lithified calcareous ooze. Facies A3: Oligocene to Miocene calcisiltite with thin tuffaceous beds, overlies Facies A2 in most areas, and also occurs in the western Solomons. This represents similar, but less lithified calcareous ooze, and the deposits of periodic andesitic volcanism.An open marine detrital association of Oligocene to Recent age occurs throughout the Solomons. This comprises two facies. Facies B1 is variably calcareous siltstone, of hemipelagic origin; and Facies B2 consists of volcanogenic clastic deposits, laid down from submarine mass flows.A third association, of shallow marine carbonates, ranges in age from Late Oligocene to Recent. Facies C1 is biohermal limestone, and Facies C2 is biostromal calcarenite.The fourth association comprises areally restricted Pliocene to Recent paralic detrital deposits. Facies D1 includes nearshore clastic sediments, and Facies D2 comprises alluvial sands and gravels.Pre-Oligocene pelagic sediments were deposited contemporaneously with, and subsequent to, the extrusion of oceanic tholeiite. Island arc volcanism commenced along the length of the Solomons during the Oligocene, and greatly influenced sedimentation. Thick volcaniclastic sequences were deposited from submarine mass flows, and shallow marine carbonates accumulated locally. Fine grained graded tuffaceous beds within the marine pelagic association are interpreted as products of this volcanism, suggesting that the Santa Isabel-Malaita-Ulawa area, where these beds are prevalent, was relatively close to the main Solomons chain at this time. A subduction zone may have dipped towards the northeast beneath this volcanic chain. Pliocene to Pleistocene calcalkaline volcanism and tectonism resulted in the emergence of all large islands and led to deposition of clastic and carbonate facies in paralic, shallow and deep marine environments.     

Origin of fine-grained carbonate and siliciclastic sediments in an Early Palaeozoic slope sequence, Cow Head Group, western Newfoundland

The Cow Head Group is an Early Palaeozoic base-of-slope sediment apron composed of carbonate and shale. Whereas coarse-grained conglomerate and calcarenite are readily interpreted as debris-flow and turbidite deposits, calcilutite (lime mudstone), calcisiltite, and shale combine to form three distinct lithofacies whose present attributes are a function of both sedimentation and early diagenesis. Shale is the most common lithology. Black, green, and red shale colour variations reflect the abundance of organic matter in the source area and oxygenation conditions of the sea bottom. In black and green shale, millimetre- to centimetre-thick, alternating dark and light laminations represent terrigenous mud turbidites and hemipelagites, respectively. The calcisiltite/shale facies is uncommon and is composed of numerous graded carbonate-shale sequences (GCSS) deposited from waning carbonate turbidites and fall-out of terrigenous muds. Some of the characteristics of ribbon and parted lime mudstones in the calcilutite/shale facies can be explained by deposition of carbonate mud from dilute turbidity currents or hemipelagic settling. Other features are diagenetic in origin. The lack of micrite in GCSS and in the interbedded shales of the calcilutite/shale facies is interpreted to reflect early dissolution of the finer carbonate from these sediments. This remobilized carbonate was precipitated locally to: lithify lime mudstone turbidites or hemipelagites; form diagenetic lime mudstone beds and nodules; cement calcisiltites; and form dolomite. Many of the calcisiltites and calcilutites were, therefore, carbonate enriched at the expense of adjacent argillaceous sediments. These attributes characterize not only fine-grained sediments of the Cow Head Group but many other Early Palaeozoic slope carbonates as well, suggesting that the model proposed here for depositionl diagenesis has wider application.     

Sediments and history of the Rottnest Shelf, southwest Australia: a swell-dominated, non-tropical carbonate margin

The Rottnest Shelf is a narrow, wave-dominated open shelf on the passive continental margin of southwest Australia, adjacent to a hinterland of low relief and sluggish drainage. High physical energy, low nutrients in cool subtropical waters, and rapid postglacial transgression have limited carbonate productivity, restricted grain types, and reworked the transgressed surface to form only a thin ( < 1 m) blanket of carbonate and relict sediment, with little terrigenous influx. Subaerial weathering of the shelf during Late Pleistocene emergence was followed by postglacial drowning, erosional shoreface retreat, and generation of a transgressive lag deposit. Establishment of the warm temperate biota, dominated by bryozoans and calcareous red algae, resulted in bioerosion of the shelf disconformity surface and generation of hardground veneers and thin skeletal carbonate sheets. Linear topographic ridges of Pleistocene limestone partition the shelf into systems with varying physical energy, biota and sediment supply. The Holocene sediments are a shallowing-upward coastal sequence; wave-ripple cross-stratified grainstone (Inner Shelf); and bioturbated bryozoan grainstone to skeletal wackestone (Outer Shelf to Upper Continental Slope), characterised by seaward fining and increasing percentages of planktic carbonate sediment.

Given sufficient time, the Rottnest Shelf could recover from drowning, and form blanket-like skeletal carbonates. Thin ( < 1 m) lags overlying disconformities, which underlie shallowing-upward coastal and shelf sediments a few metres thick, will be generated by glacio-eustatic cycles of sedimentation (10⁵ y duration). Thick (several tens of metres) sediment bodies, composed of wave-rippled to bioturbated skeletal carbonate sediment with a temperate biota, will be formed during longer term (1–10 My) sedimentation cycles. Such cycles have characterised passive margins during the Cenozoic. The Rottnest Shelf thus provides a facies model for temperate shelf sedimentation along passive continental margins.     

Types of Holocene deposits and regional pattern of sedimentation in Lake Baikal

Results of research into recent sediments and their distribution in Lake Baikal are presented. Five areas with different mechanisms of sedimentation have been recognized: (1) deep-water plains with pelagic mud and turbidites; (2) littoral zones without turbidites; (3) underwater ridges (rises) with hemipelagic mud accumulated under calm sedimentation conditions; (4) delta (fan) areas near the mouths of large rivers, where sediments consist mainly of terrigenous material; and (5) shallow Maloe More with poorly sorted terrigenous material and abundant sand. The rate of sedimentation differs considerably in different Baikal areas. The highest rates appear near the mouths of large rivers, lower ones occur in the deep lake basins, and the minimum rates are developed on underwater ridges. A map of the distribution of Holocene sediments in Baikal has been compiled for the first time. The obtained results show that the bottom morphology significantly determines the type of sediments in the lake.     

Carbonates within a Pleistocene glaciomarine succession, Yakataga Formation, Middleton Island, Alaska

Uplifted during the 1964 Alaskan earthquake, extensive intertidal flats around Middleton Island expose 1300 m of late Cenozoic (Early Pleistocene) Yakataga Formation glaciomarine sediments. These outcrops provide a unique window into outer shelf and upper slope strata that are otherwise buried within the south‐east Alaska continental shelf prism. The rocks consist of five principal facies in descending order of thickness: (i) extensive pebbly mudstone diamictite containing sparse marine fossils; (ii) proglacial submarine channel conglomerates; (iii) burrowed mudstones with discrete dropstone layers; (iv) boulder pavements whose upper surfaces are truncated, faceted and striated by ice; and (v) carbonates rich in molluscs, bryozoans and brachiopods. The carbonates are decimetre scale in thickness, typically channellized conglomeratic event beds interpreted as resedimented deposits on the palaeoshelf edge and upper slope. Biogenic components originated in a moderately shallow (ca 80 m), relatively sediment‐free, mesotrophic, sub‐photic setting. These components are a mixture of parautochthonous large pectenids or smaller brachiopods with locally important serpulid worm tubes and robust gastropods augmented by sand‐size bryozoan and echinoderm fragments. Ice‐rafted debris is present throughout these cold‐water carbonates that are thought to have formed during glacial periods of lowered sea‐level that allowed coastal ice margins to advance near to the shelf edge. Such carbonates were then stranded during subsequent sea‐level rise. Productivity was enabled by attenuation of terrigenous mud deposition during these cold periods via reduced sedimentation together with active wave and tidal‐current winnowing near the ice front. Redeposition was the result of intense storms and possibly tsunamis. These sub‐arctic mixed siliciclastic‐carbonate sediments are an end‐member of the Phanerozoic global carbonate depositional realm whose skeletal attributes first appeared during late Palaeozoic southern hemisphere deglaciation.     

南海北部大陆架现代礁源碳酸盐与陆源碎屑的混合沉积作用

在南海北部大陆架陆源碎屑沉积占优势的背景上，在珊瑚岸礁和堡礁周围，广泛发育着礁源碳酸盐和陆源碎屑组成的混合沉积。它们以砂屑、砂砾屑结构为主并含有生物格架结构。混合沉积的形成条件是具备碳酸盐和硅质碎屑两类物源，活跃的水动力，干湿交替的气候，此外，海平面的相对波动，也会造成积极的影响。混合沉积方式有随机式、相变式和随机 - 相变式等三种。混合沉积体常是多种混合方式交替、叠加而成的沉积复合体。礁源与陆源混合沉积相模式是从岸礁 - 堡礁相模式基础上发展而来，按沉积相和沉积结构可以分为五种混合沉积：1)礁基混积岩和礁格架混积岩，2）礁坪砂砾屑混积岩，3）礁后海滩 - 沙堤砾砂屑混合沉积，4）礁后泻湖砂屑混合沉积和5）礁前（翼）浅海砂屑混合沉积。礁源与陆源混合沉积的鉴别标志是珊瑚骨屑和岩屑各占10 - 50 ％，其它生物碎屑不计。南海大陆架现代混合沉积是一个典型的实例，可为全面研究现代南海沉积学和比较沉积学提供依据。     

Major controls on sedimentation during the evolution of a continental basin: Pliocene–Pleistocene of the Guadix Basin (Betic Cordillera, southern Spain)

Sequence stratigraphy, based on climatic, tectonic, and base level parameters, can be used to understand carbonate sedimentation in continental basins. The uppermost continental fill of the Guadix Basin (Betic Cordillera), containing both siliciclastics and carbonates, is investigated here. In its central sector a thick succession of fluvio-lacustrine sediments appear, hosting several important Pliocene and Pleistocene macrovertebrate sites (Fonelas Project). The need to characterize the stratigraphic and sedimentologic context of these important paleontologic sites has lead to litho-, magneto- and biostratigraphic studies. These data, together with the sedimentologic analysis of the Pliocene and Pleistocene siliciclastic and carbonate successions, establish a sedimentary model for the fluvio-lacustrine sedimentation of the two last stages of sedimentation in the Guadix Basin (Units V and VI). Unit V comprises mostly fluvial siliciclastic sediments with less abundant carbonate beds interpreted as floodplain lakes or ponds. The latter, Unit VI, is dominated by vertically-stacked, carbonate palustrine successions. Using two pre-existent continental stratigraphic models, the influence of climate, tectonism, and stratigraphic base level during the last 3.5 Ma on the sedimentary evolution of the fluvio-lacustrine system in the Guadix Basin, especially the carbonate sedimentation patterns, is outlined.     

Quaternary sediments in the northwestern part of the Barents Sea and their relation to the underlying Mesozoic bedrock

A sedimentological study of Quaternary sediments from the northwestern part of the Barents Sea shows that their composition is controlled by the underlying Mesozoic bedrock and that very little sediment has been supplied from outside sources. The Quaternary sediments consist of Pleistocene glacial clays (moraines) and Holocene gravel, sand and mud, derived by erosion of the clay-rich moraines, which again have been derived from underlying Mesozoic rocks. On the shallow Spitsbergen Bank (30-100 m depth) we find a high energy facies of bioclastic carbonate sand and gravel and lag deposits of Mesozoic rock fragments from the underlying moraine. ¹⁴C-datings of the bioclastic carbonates (Molluscs and Barnacles) suggest that soft bottom conditions with Mya truncata prevailed in early Holocene time, succeeded by a hard bottom high energy environment with Barnacles in the last 2000-3000 years. This may be due to a southward movement of the oceanic polar front into the Spitsbergen Bank due to colder climate in Late Holocene (subatlantic) time, which at present day produces strong bottom currents down to 100 m depth. On the Spitsbergen Bank carbonate sedimentation has succeeded glacial sedimentation as a result of withdrawal of clastic sediment supply in Holocene time and high organic productivity because of upwelling. A similar mechanism may have been operating during earlier glaciations, i.e. in Late Precambrian time to produce an association of glacial and carbonate sediments although the biological precipitation was different at that time. In Late Precambrian time precipitation or carbonate by algaes may have occurred in colder water on the shelves due to higher saturation of carbonate in the sea water.     

BASIN-RANGE TRANSITION AND GENETIC TYPES OF SEQUENCE BOUNDARY OF THE QIANGTANG BASIN IN NORTHERN TIBET

BASIN-RANGE TRANSITION AND GENETIC TYPES OF SEQUENCE BOUNDARY OF THE QIANGTANG BASIN IN NORTHERN TIBET     

Carbonate deposition and facies distribution in a central Michigan marl lake

Relatively pure lacustrine carbonates referred to as marl are being deposited in Littlefield Lake, central Michigan, a hard-water lake with little terrigenous clastic influx. Thick accumulations of marl form both progradational marl benches along lake margins, and islands or lakemounts in the lake centre. Marl benches develop flat platforms up to 20 m wide in very shallow water and steeply inclined slopes, up to 30°, extending into deep water. The flat landward platform is frequently covered by algal pisoliths while the upper portion of the lakeward-sloping bottom is overgrown by Chara which in the summertime becomes thickly encrusted with low-magnesian calcite. Marl islands are flat-topped features that formed over relict highs on Pleistocene drift which underlies the lake basin. These are fringed by marl benches identical to those found along lake margins. Marl benches are composed of four units: two thin facies deposited on the shallow-water bench platform and two thicker faces deposited on the bench slope developed in moderate water depths. These in turn overlie a fifth facies deposited in deep water. A coarsening-upward sequence is developed in these sediments as a result of both mechanical sorting, and primary production of carbonate sand and gravel in shallow water. In addition to facies sequences and size grading, trends upsection of increasing carbonate content and decreasing insoluble content may serve to identify temperate-region lacustrine carbonate deposits in the rock record.     

Geochemical factors for endogenic mineral formation in the bottom sediments of the Tazheran lakes (Baikal area)

We studied recent sedimentation in small saline and brackish lakes located in the Ol’khon region (western Baikal area) with arid and semiarid climate. The lakes belong to the Tazheran system; it is a series of compactly located closed shallow lakes, with a limited catchment area and different mineralization, under the same landscape, climatic, geologic, and geochemical conditions. Two complementary approaches are applied in the research: (1) a detailed study of individual lake and (2) a comparison of the entire series of lakes, which can be considered a natural model for studying the relationship between endogenic mineral formation and the geochemistry of lake waters. The lake waters and bottom sediments were studied by a set of modern methods of geochemistry, mineralogy, and crystal chemistry. The mineral component of the bottom sediments was analyzed by powder X-ray diffraction (XRD), IR spectroscopy, and electron microscopy. The lakes are characterized by predominant carbonate sedimentation; authigenic pyrite, smectite, chlorite, and illite are detected in assemblage with carbonate minerals in the bottom sediments. Carbonate phases have been identified, and their proportions have been determined in the samples by decomposition of the complex XRD profiles of carbonate minerals into peaks using the Pearson VII function. Mathematical modeling of the XRD profiles of carbonates has revealed that predominantly Mg-calcites with variable Mg content and excess-Ca dolomite accumulate in lake bottom sediments influenced by biogenic processes. Aragonite, monohydrocalcite, and rhodochrosite form in some lakes along with carbonates of the calcite-dolomite series. We show a dependence of the composition of the assemblages of the newly formed endogenic carbonate minerals and their crystallochemical characteristics on the chemical composition of lake waters.     

高密度流与湖南泥盆纪沉积相分异

湖南泥盆纪陆表海的沉积相分异,尤其是台地相和台盆相的分异与当时发育的高密度流有密切的关系,高密度流的流动和沉积又与地形及海侵海退有关。高密度流使台盆区形成与相邻的台地区完全不同的沉积,形成的沉积差异反过来又使海底地形发生进一步的变化。在这种反复作用的过程中,湖南泥盆纪的岩相分异经历了一个形成、发展、消减直至结束的过程     

Neritic and pelagic carbonate sedimentation in the marine environment: ignorance is not bliss

Synthesis of available data allows us to define general patterns of late Quaternary carbonate production and sedimentation in the global ocean. During high stands of sea level, the neritic and pelagic environments appear to sequester approximately similar amounts of carbonate, whereas during low stands of sea level the decreased neritic zone produces and accumulates approximately an order of magnitude less carbonate. Assuming that global accumulation of deep-sea carbonates remains more or less constant during glacially induced changes in sea level, the ocean becomes depleted with respect to calcium carbonate during high stands and recharges during low stands. Before we can achieve a better understanding of the global carbonate system, however, we need a better understanding of key environments and processes: (a) production and accumulation on continental shelves both as potential sinks (accumulation) and as sources (export to the deep sea); (b) a better measure of pelagic carbonate production; and (c) late Quaternary (late Pleistocene and Holocene) mass accumulation rates in the deep sea.     

Temperate shelf carbonate sediments in the Cenozoic of New Zealand

Shelf limestones are widely distributed in New Zealand Cenozoic sequences and are especially well developed in the Oligocene. Detailed field and laboratory work on several Oligocene occurrences, and reconnaissance field-work at most other sections have elucidated the major characteristics of the environment, texture, composition and diagenesis of these sediments. Several generalizations emerge which contrast with the commonly accepted characteristics of shallow marine carbonate sedimentation established from studies of tropical and subtropical deposits. The limestones are either calcarenites or, less commonly, calcilutites and, in general, these two lithologies are mutually exclusive, both in time and space. The allochems and interparticle carbonate mud (where developed) in calcarenitic limestones consist almost exclusively of fragmented skeletal material derived primarily from bryozoan, echinodermal, benthic foraminiferal, barnacle, brachiopod, bivalve and coralline red algal tests. The calcilutitic limestones consist mainly of whole and disintegrated tests of pelagic foraminifers and coccolithophorids. Non-skeletal carbonate components such as ooids, pellets and aggregates are conspicuously absent from both lithologies. Reefal structures are also absent or rare and are mainly oyster reefs. The limestones commonly contain a significant content of terrigenous material and/or glauconite and at the stratigraphic level the limestones are intimately associated with terrigenous formations. The distribution of the carbonate sediments has been governed mainly by rate of supply of river-derived terrigenous material, by subsequent dispersal patterns of this material over the shelf, and by current sorting. As a consequence of selective grain transport, bedding in the limestones is often defined by the cyclic alternation on a wide range of scales of carbonate units that are relatively enriched and relatively impoverished in terrigenous material. The primary (carbonate) mineralogy of the carbonate sediments was completely dominated by magnesium calcite and/or calcite with only small amounts of aragonite and no dolomite or associated evaporite minerals. The metastable magnesium calcite and aragonite grains were probably altered on, or close below, the shallow sea-floor. Among other factors, transformation was encouraged by the absorption of magnesium in pore waters by montmorillonitic clays and by the complete oxidation of all organic matter in the bottom sediments. Magnesium calcite grains were stabilized by texturally non-destructive incongruent dissolution, but aragonite was often dissolved without trace from the sediment, especially in grainstones. Thus submarine diagenesis has been characterized by selective dissolution phenomena. Cementation by granular and syntaxial rim orthosparite of calcite and/or ferroan calcite composition occurred mainly during shallow subsurface burial and was associated with the intergranular solution of calcitic skeletal fragments, especially at those levels in the sediment relatively enriched in terrigenous material. This lithification process has worked to accentuate and modify original litho-logic differences and sedimentary structures in the primary sediments and has produced a kind of rhythmic vertical alternation of less well cemented, microstylolitized, impure limestone beds (‘cement-donor’ beds) and well cemented, more open textured, purer limestone beds (‘cement-receptor’ beds). The New Zealand limestones formed between latitudes 60° S and 35° S under generally cool temperate to warm temperate climate conditions. Oxygen isotopes suggest that surface waters were mainly significantly cooler than 20°C, so that shelf waters may have experienced extended periods of undersaturation with respect to calcium carbonate. Generally open circulation patterns maintained near normal salinity values over the entire shelf platform. Calculated sedimentation rates for the New Zealand carbonate sediments are generally very low (< 5 cm/1000 years). Periods of more active deposition commonly alternated with longer periods of non-deposition and by-passing or erosion. It is concluded that many characteristics of the New Zealand shelf limestone occurrences are explained best by a temperate latitude model of shallow marine carbonate sedimentation.