Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals

The stable nitrogen and carbon isotope ratios of bone collagen prepared from more than 100 animals representing 66 species of birds, fish, and mammals are presented. The δ¹⁵N values of bone collagen from animals that fed exclusively in the marine environment are, on average, 9%. more positive than those from animals that fed exclusively in the terrestrial environment; ranges for the two groups overlap by less than 1%. Bone collagen δ¹⁵N values also serve to separate marine fish from the small number of freshwater fish we analyzed. The bone collagen δ¹⁵N values of birds and fish that spent part of their life cycles feeding in the marine environment and part in the freshwater environment are intermediate between those of animals that fed exclusively in one or the other system. Further, animals that fed at successive trophic levels in the marine and terrestrial environment are separated, on average, by a 3%. difference in the δ¹⁵N values of their bone collagen. Specifically, carnivorous and herbivorous terrestrial animals have mean δ¹⁵N values for bone collagen of + 8.0 and + 5.3%., respectively. Among marine animals, those that fed on fish have a mean δ¹⁵N value for bone collagen of + 16.5%., whereas those that fed on invertebrates have a mean δ¹⁵N value of + 13.3%. These results support previous suggestions of a 3%. enrichment in δ¹⁵N values at each successively higher trophic level. In contrast to the results for δ¹⁵N values, the ranges of bone collagen δ¹³C values from marine and terrestrial feeders overlap to a great extent. Additionally, bone collagen δ¹³C values do not reflect the trophic levels at which the animals fed. These results indicate that bone collagen δ¹⁵N values will be useful in determining relative dependence on marine and terrestrial food sources and in investigating trophic level relationships among different animal species within an ecosystem. This approach should be applicable to animals represented by prehistoric or fossilized bone in which collagen is preserved.     

Characterization of the hydrogen isotopic composition of individual n-alkanes in terrestrial source rocks

In order to characterize the H isotopic compositions of individual lipid compounds from different terrestrial depositional environments, the δD values of C-bound H in individual n-alkanes from typical terrestrial source rocks of the Liaohe Basin and the Turpan Basin, China, were measured using gas chromatography–thermal conversion–isotope ratio mass spectrometry (GC–TC–IRMS). The analytical results indicate that the δD values of individual n-alkanes in the extracts of terrestrial source rocks have a large variation, ranging from −140‰ to −250‰, and are obviously lighter than the δD of marine-sourced n-alkanes. Moreover, a trend of depletion in ²H(D) was observed for individual n-alkanes from different terrestrial depositional environments, from saline lacustrine to freshwater paralic lacustrine, and to swamp. For example, the δD values of n-alkanes from a stratified saline lacustrine environment vary from −140‰ to −200‰, δD for n-alkanes from swamp facies range from −200‰ to −250‰, while those from freshwater paralic lacustrine–lacustrine environments fall between the δD values of the end members. The shift toward lighter δD from saltwater to freshwater environments indicates that the source water δD is the major controlling factor for the H isotopic composition of individual compounds. In addition, H exchange between formation water and sedimentary organic matter may possibly be important in regard to the δD of individual n-alkanes. Therefore, other lines of geochemical evidence must be considered when depositional paleoenvironments of source rocks are reconstructed based on the H isotopic composition of individual n-alkanes.     

Proteins as a possible source material of low molecular weight petroleum hydrocarbons

Low temperature cracking experiments of a representative protein, at temperatures not far above the observed temperature range of 130–160°C of mature California oil source rocks, indicate the formation of all gaseous and of some gasoline range hydrocarbons of petroleum. Based on protein derivatives only it is estimated that a maximum of at least 3–8% by weight of the total organic matter of oil source sediments may be converted into such hydrocarbons. This is in addition to hydrocarbons originating from lipids.     

The influence of air mass source on the seasonal isotopic composition of precipitation, eastern USA

As part of the AIRMoN program, daily precipitation samples have been collected since the early 1990s throughout the eastern and central United States. Using precipitation stable isotope (δ¹⁸O and δD) and HYSPLIT back trajectory analysis of 591 samples collected by the AIRMoN program from Florida, Illinois, Pennsylvania, Tennessee, Vermont, and West Virginia, amount weighted seasonal average isotopic compositions were calculated for precipitation from Continental, Pacific, Gulf of Mexico, Arctic, North Atlantic, and Mid Atlantic sources. Our results suggest that these sources are isotopically distinct and variable at and among most sites during most seasons. However, in many instances, the isotopic differences of the sources require dramatic changes in precipitation amounts from these sources to modify the seasonal average isotopic composition at a particular site. The relative importance of each source type to the seasonal average isotopic composition is highly variable among and within sites. The largest differences in the isotopic compositions of different sources are in winter and spring precipitation from the high latitude sites. At the Vermont location, the seasonal average isotopic composition is potentially quite sensitive to the relative amounts of precipitation from Arctic and Gulf of Mexico sources.     

中国海相超深层油气形成

超深层是指现今或曾经埋藏深度超过6000 m的沉积地层。中国海相超深层时代老,热演化程度高,经历的构造运动多,独特的构造-沉积和生烃环境,决定了海相超深层油气藏形成与分布的复杂性,成烃-成储-成藏规律明显不同于中浅地层,勘探的难度也远远大于国外中新生代克拉通盆地。经过半个多世纪的探索,近年来中国海相超深层油气勘探在中西部盆地取得一系列重大突破,显著提升了超深层领域油气资源的战略地位。与此同时,中国海相超深层油气地质理论也取得重大进展,形成了以重大地质转折期构造活动控制超深层油气地质要素发育、深埋高温环境导致多途径天然气生成、沉积-构造作用控制超深层油气储集空间形成与保持、超深层温压系统控制油气藏相态演化和多期成藏、多层系分布等为核心的理论认识,极大地发展了国外学者基于中新生代海相地层提出的油气生成与成藏模式,拓展了海相油气资源形成和分布的时空界限。     

The Hf-Nd isotopic composition of marine sediments

This paper presents new major and trace-element data and Lu-Hf and Sm-Nd isotopic compositions for representative suites of marine sediment samples from 14 drill sites outboard of the world’s major subduction zones. These suites and samples were chosen to represent the global range in lithology, Lu/Hf ratios, and sediment flux in subducting sediments worldwide. The data reported here represent the most comprehensive data set on subducting sediments and define the Hf-Nd isotopic variations that occur in oceanic sediments and constrain the processes that caused them.Using new marine sediment data presented here, in conjunction with published data, we derive a new Terrestrial Array given by the equation, ε_Hf = 1.55 × ε_Nd + 1.21. This array was calculated using >3400 present-day Hf and Nd isotope values. The steeper slope and smaller y-intercept of this array, compared to the original expression (ε_Hf = 1.36 × ε_Nd + 2.89; Vervoort et al., 1999) reflects the use of present day values and the unradiogenic Hf of old continental samples included in the array.In order to examine the Hf-Nd isotopic variations in marine sediments, we have classified our samples into 5 groups based on lithology and major and trace-element geochemical compositions: turbidites, terrigenous clays, and volcaniclastic, hydrothermal and hydrogenetic sediments. Compositions along the Terrestrial Array are largely controlled by terrigenous material derived from the continents and delivered to the ocean basins via turbidites, volcaniclastic sediments, and volcanic inputs from magmatic arcs. Compositions below the Terrestrial Array derive from unradiogenic Hf in zircon-rich turbidites. The anomalous compositions above the Terrestrial Array largely reflect the decoupled behavior of Hf and Nd during continental weathering and delivery to the ocean. Both terrigenous and hydrogenetic clays possess anomalously radiogenic Hf, reflecting terrestrial sedimentary and weathering processes on the one hand and marine inheritance on the other. This probably occurs during complementary processes involving preferential retention of unradiogenic Hf on the continents in the form of zircon and release of radiogenic Hf from the breakdown of easily weathered, high Lu-Hf phases such as apatite.     

The influence of marine inflows on the chemical composition of groundwater in small islands: the example of the Cyclades (Greece)

 Marine contamination of groundwater may be caused by seawater intrusion and by salt spray. The role of both processes was studied in the Cyclades archipelago on four small islands (45–195 km²) whose aquifers consist essentially of fractured, weathered metamorphic rocks. Annual rainfall ranges from 400 to 650 mm and precipitation has high total dissolved solids contents of 45–223 mg l^–1. The chemical characteristics of the groundwater, whose salinity is from 0.4 to 22 g l^–1, are strongly influenced by seawater intrusion. However, the effect of atmospheric input is shown in certain water sampling locations on high ground elevation where the dissolved chloride contents may attain 200 mg l^–1. Received: 14 November 1995 · Accepted: 9 September 1996     

Microspectrofluorescence measurements of coals and petroleum source rocks

Good, reproducible microspectrofluorescence data, similar to published fluorescence trends, are obtainable from samples of coals and petroleum source rocks (shales). These data are reproducible when measured by different operators, different instruments, or at different times (for example, the remeasurement of samples several months apart). These fluorescence data are used to predict maturity or rank to within about 0.10% R₀ (mean vitrinite reflectance, oil immersion). Commercially available computerized fluorescence equipment, with customized software and specific hardware mod modifications, makes the acquisition of fluorescence data feasible. Fluorescence can be used for measuring low-maturity samples, in which the measurement of vitrinite reflectance is difficult. Source rocks from oil-rich basins frequently do not contain enough particles of vitrinite for a reflectance determination, but they may contain fluorescing particles which can be measured. Although the results from only two different kinds of fluorescence equipment (Zeiss Zonax and Vickers Gamma-Scientific) are discussed, any instrument with equivalent stability and sensitivity can be used to attain reproducible and accurate fluorescence data.We propose the use of the term “R_F” to report fluorescence data in equivalent vitrinite reflectance values. Although the principles and techniques of measuring fluorescence were introduced several years ago, much work remains to establish standardized methods of maesuring as well as data evaluation. The current method of reporting fluorescence data in terms of spectral characteristics (such as the wavelength of maximum intensity or wavelength ratios) is awkward to use and difficult to compare results from various laboratories. R_F values convey rank or maturation meaning and can be easily compared among laboratories.Data from fluorescing grains in both coal and petroleum source rock samples are given in this study. Polished samples of coal, this sections, and kerogen strewn slides of source rocks are measured. Spectral data are evaluated by four parameters: the wavelength of maximum intensity (Peak), the red/green ratio (Q), the coordinates of a metric color system (CIE), and the relative intensity at 490 nm. The measurement of intensity, reported in units of radiance, is possible with the Vickers Gamma-Scientific instrument. Measuring both fluorescent colors (R_F) and intensities may help explain some of the relationships among organic particles, maturation, and hydrocarbon generation.     

西藏那茶淌铅锌矿床S-Pb同位素组成及其示踪成矿物质来源

那茶淌矿床位于西藏冈底斯–念青唐古拉成矿带东段,为近年发现的具中—大型远景规模的矽卡岩型铅锌矿床,其成矿物质来源及其成矿背景还缺乏详细调查,制约了矿床成因的深入研究。本文在矿床地质特征研究基础上,对矽卡岩型矿石中主要金属矿物闪锌矿、方铅矿、磁黄铁矿的S、Pb同位素组成进行分析,探讨矿床成矿物质来源,并与区域上典型铅锌矿床进行对比,总结区域成矿规律。结果显示,那茶淌矿床金属硫化物的δ³⁴S（‰）值变化于－1.6‰～4.2‰之间,平均值为1.4‰,其频率直方图呈正太分布形式,具幔源硫特征。金属硫化物的²⁰⁶Pb/²⁰⁴Pb值为18.548～18.792,平均值为18.691;²⁰⁷Pb/²⁰⁴Pb值为15.683～15.856,平均值为15.755;²⁰⁸Pb/²⁰⁴Pb值为39.049～39.685,平均值为39.331;铅同位素特征值μ的变化范围为9.61～9.93,平均值为9.74,所有样品μ值均高于9.58,显示铅源具有上地壳源区物质的特征。通过区域成矿作用对比研究,那茶淌矿床S、Pb同位素组成与念青唐古拉带东段典型矽卡岩型铅锌矿床具有相似的特征,成矿物质主要来源于念青唐古拉群结晶基底物质的重熔。

     

The influence of pressure and composition on the viscosity of andesitic melts

The effect of pressure and composition on the viscosity of both anhydrous and hydrous andesitic melts was studied in the viscosity range of 10⁸ to 10^11.5 Pa · s using parallel plate viscometry. The pressure dependence of the viscosity of three synthetic, iron-free liquids (andesite analogs) containing 0.0, 1.06, and 1.96 wt.% H₂O, respectively, was measured from 100 to 300 MPa using a high-P-T viscometer. These results, combined with those from Richet et al. (1996), indicate that viscosities of anhydrous andesitic melts are independent of pressure, whereas viscosities of hydrous melts slightly increase with increasing pressure. This trend is consistent with an increased degree of depolymerization in the hydrous melts. Compositional effects on the viscosity were studied by comparing iron-free and iron-bearing compositions with similar degrees of depolymerization. During experiments at atmospheric and at elevated pressures (100 to 300 MPa), the viscosity of iron-bearing anhydrous melts preequilibrated in air continuously increased, and the samples became paramagnetic. Analysis of these samples by transmission electron microscopy showed a homogeneous distribution of crystals (probably magnetite) with sizes in the range of 10 to 50 nm. No significant difference in the volume fractions of crystals was found in samples after annealing for 170 to 830 min at temperatures ranging from 970 to 1122 K. An iron-bearing andesite containing 1.88 wt.% H₂O, which was synthesized at intrinsic fO₂ conditions in an internally heated pressure vessel, showed a similar viscosity behavior as the anhydrous melts. The continuous increase in viscosity at a constant temperature is attributed to changes of the melt structure due to exsolution of iron-rich phases. By extrapolating the time evolution of viscosity down to the time at which the run temperature was reached, for both the anhydrous (at 1055 K) and the hydrous (at 860 K) iron-bearing andesite, the viscosity is 0.7 log units lower than predicted by the model of Richet et al. (1996). This may be explained by differences in structural properties of Fe²⁺ and Fe³⁺ and their substitutes Mg²⁺, Ca²⁺, and Al³⁺, which were used in the analogue composition.The effect of iron redox state on the viscosity of anhydrous, synthetic andesite melts was studied at ambient pressure using a dilatometer. Reduced iron-bearing samples were produced by annealing melts in graphite crucibles in an Ar/CO atmosphere for different run times. In contrast to the oxidized sample, no variation of viscosity with time and no exsolution of iron oxide phases was observed for the most reduced glasses. This indicates that trivalent iron promotes the exsolution of iron oxide in supercooled melts. With decreasing Fe³⁺/ΣFe ratio from 0.58 to 0.34, the viscosity decreases by ∼1.6 log units in the investigated temperature range between 964 and 1098 K. A more reduced glass with Fe³⁺/ΣFe = 0.21 showed no additional decrease in viscosity. Our conclusion from these results is that the viscosity of natural melts may be largely overestimated when using data obtained from samples synthesized in air.     

Changes in gas composition during simulated maturation of sulfur rich type II-S source rock and related petroleum asphaltenes

Asphaltenes extracted from crude oils are proposed to possess structural features of the related source rock kerogen. For the present study micro-scale sealed vessel pyrolysis (MSSV) and combustion isotope ratio mass spectrometry (GC–C–IRMS) were used to compare gas generation from a whole rock (type II-S kerogen) from southern Italy with that from related sulfur rich asphaltenes isolated from a low maturity heavy crude oil. The purpose of was to determine whether experimental pyrolysis of oil asphaltenes can be used to predict the timing and the chemical and isotopic composition of hydrocarbon gases generated from genetically related kerogen in the source rock during burial maturation. The results show that parameters such as (gas to oil ratio) GOR and oil and gas formation timing are very similar for these two sample types, whereas gas composition, product aromaticity and sulfur content are remarkably different. Slight differences in GOR are mainly due to differences in gas formation characteristics at very high levels of thermal alteration. Secondary gas formation from the whole rock covers a much broader temperature range under geological conditions than that from the asphaltene products. However, it is remarkable that both the onset and the maximum temperature are nearly identical under geological conditions. The observed differences in gas generation characteristics are supported by discrepancies in the carbon isotopic characteristics of the gas range compounds and indicate different precursors and/or mechanisms for gas generated from whole rock and asphaltenes.     

Structure proof and significance of stereoisomeric 28,30-bisnorhopanes in petroleum and petroleum source rocks

Two C₂₈H₄₈-pentacyclic triterpanes were isolated from Monterey shale. X-ray crystallography of a crystal containing both compounds proved their structures as 17β,18α,21α(H)-28,30-bisnorhopane and 17β,18α,21β(H)-28,30-bisnorhopane. Several differences are found between 28,30-bisnorhopanes and the regular hopanes. Unlike the regular hopane epimers, for practical purposes the three epimeric 28,30-bisnorhopanes [17α,21β(H)-, 17β,21α(H)-, and 17β,21β(H)-]cannot be distinguished by their mass spectra. Special conditions are needed to separate them by gas chromatography. The diagenetically first-formed epimer is thought to be 17α,21β(H)- because it predominates in immature shales. The order of thermodynamic stability is 17β,2lα(H) < > 17α,21β(H) > 17β,21β(H), and all three epimers are present in petroleum. 25,28,30-Trisnorhopanes can be analyzed in similar fashion and are found to have similar thermodynamic characteristics. The percent of the ring D/E cis epimer of 28,30-bisnorhopane and/or 25,28,30-trisnorhopane is a useful maturation parameter similar to the 20S/20R sterane ratio. Evidence indicates 25-demethylation of 28,30-bisnorhopane to 25,28,30-trisnorhopane during advanced stages of biodegradation. Hence, percent ring $\text{D}\text{E}$cis 25,28,30-trisnorhopane has an application to maturation assessment in heavily biodegraded oils.     

Push-moraines and glacier-contact fans in marine and terrestrial environments

ABSTRACT The local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts, which in turn determine the sediments and landforms produced at the glacier front. Many modern glaciers undergoing overall retreat in areas of'maritime'climate produce winter push moraines during a late winter readvance, followed by a summer retreat, whilst in more'continental'regions no significant winter readvance occurs and annual push-moraines are absent. The frontal dynamics which lead to these changes are analysed and the form, structure, sequence and field relations of both terrestrial and marine push-moraines are described from Iceland, Spitsbergen and Baffin Island.
Long-term changes in mass balance leading to major glacier advances or readvances also generate large push-moraines. In terrestrial environments push-moraine formation is accompanied by uplift, rejuvenation and down-cutting of outwash systems whose sediments become closely associated with glaciotectonic structures, which permit pre-, syn- and post-tectonic sequences to be identified.
The development of ice marginal fan/moraine complexes is modelled as a function of the relative magnitude of two parameters: the velocity of ice movement and the calving rate. A high ice velocity just exceeded by the calving rate gives closely spaced push-moraines and confluent ice marginal fans. A high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans. A low ice velocity in combination with a high calving rate results in well separated and feebly developed push-moraines, while a low ice velocity and a low calving rate produces feeble push-moraines and coalescent fans.     

The regularities in the structural group composition of high-molecular heteroatomic petroleum components

We generalized experimental data on the structural group composition and macrostructural characteristics of high-molecular compounds (HMCs)—hydrocarbons, resins, and asphaltenes—from more than 180 crude oil samples extracted from different oil fields of Eurasia. Most of oil resin molecules contain 1–3 structural blocks, each consisting of 0–3 aromatic and 0–5 naphthenic rings in different combinations, with the total number of rings in each block not exceeding 5–6. The average molecular weights of resins are no more than 100–1500 a.m.u. Asphaltenes differ from resins from the same source in the larger number of structural blocks (mainly tri- or tetracyclic aromatic) in molecule (up to five), lower degrees of substitution of aromatic cores, and smaller portions of carbon atoms in saturated fragments. The average molecular weights of asphaltenes measured by naphthalene cryoscopy do not exceed 2500 a.m.u. Owing to intermolecular interactions, HMCs form various associates and polymolecular particles, including quasi-crystalline “batches” and multibatch aggregates. Spontaneous disintegration and formation of such particles make the oils dynamically equilibrium polydisperse systems. We have developed the main regularities of compositional and structural changes of HMCs depending on the depth of occurrence, age, and lithologic composition of oil-bearing deposits. Being chemically labile heteroatomic substances, petroleum HMCs are more rapidly subjected to compositional and structural transformations than hydrocarbons, i.e., are more responsive to changes in strata conditions.     

Catagenesis and composition of petroleum: Origin of n-alkanes and isoalkanes in petroleum crudes

Distribution of n-alkanes and isoalkanes in ca. 50 petroleum crudes have been examined by the gas chromatography. Molar distributions of n-alkanes with respect to their c atom numbers in the majority of crudes follow the exponential law, which signifies a random, chemical nature of n-alkane-generating processes occurring in the catagenesis stage of petroleum maturation. Similar distributions of n-alkanes were found in the products of mild thermolysis of heavy n-alkanes.Isoalkanes represent a major, 10–25%, petroleum component. The principal types of isoalkanes in crudes are monomethyl-branched, with the branches randomly positioned in the chains, and dimethyl-branched with one of the methyl groups predominantly in the second position in the chains. Thermolysis studies of individual n-alkanes, alkanoic acids, and esters in the presence of various minerals provided an explanation of the n-alkane and isoalkane distributions. Selected heavy n-alkanes are initially formed in decarboxylation reactions of heavy n-alkanoic acids and esters. Extensive thermocracking produces mixtures of lighter n-alkane and α-olefins. The olefins, in the presence of acidic clays, are converted in cationic reactions into mixtures of predominantly mono- and dimethyl-branched isoalkanes.     

地下水污染羽对傍河水源地的影响

以西北某城市傍河水源地及其上游原油储备库为研究区,利用地下水数值模拟软件GMS建立了地下水流和溶质运移耦合模型。根据不同的水源地地下水开采方案,应用危害最大化原则,预测未来10年内原油储备库地下水中有机污染羽对水源地的影响。结果表明,虽然原油储备库距离水源地较近,但由于原油储备库所在区域仅有薄层含水层,而水源地处于其下游的断陷盆地内,形成了特殊的水文地质结构。这使得原油储备库地下水向下游的补给十分有限。水源地地下水补给主要来自北面的黄河,即使水源地加大开采也只能对石油污染羽产生很小的拉动作用。在这种情况下,10年之内原油储备库污染羽不会污染水源地地下水。从长远考虑,为增加水源地的供水安全,应恢复黄河南河道,在增加水源地补给的同时,也在水源地与污染场地之间形成天然的水力屏障,可以从根本上防止有机污染羽对水源地的威胁。     

关注苏皖南部地区海相油气资源

据苏皖南部地区地表露头及部分井下所发现的海相油气显示表明,这里存在海相油气资源勘探远景,关注这一地区的海相油气资源,如何开展和寻找这类油气资源,将有利于该地区区域性经济建设的可持续发展。     

中国南方海相油气地质基本特征与有效性研究

中国南方海相沉积盆地形成演化与扬子板块的离散、聚合及周缘山系的形成密切相关,在早古生代被动陆缘发育阶段、挤压前陆盆地台内坳陷沉积盆地发育阶段及晚古生代陆内裂陷盆地发育阶段构成了现今南方海相沉积区的主要烃源岩,有效与否在于后期改造过程的演化及保存程度.在纵向上形成了上、下两个含油气组合.海相沉积经受多期次的构造运动叠加、...     

Relationship between petroleum reservoir rocks and source rocks

A substantial fraction of sandstones containing commercial quantities of oil are proposed to be in contact with source rocks which produce oil. For these situations the quantity of oil collected in a sandstone is proportional to the area of contact with a source rock of relatively low permeability, rather than to the total thickness of the potential source rock. It is inferred that source rocks along the upper or lower faces of a sandstone should produce more oil into the sandstone than source rocks lateral to the sandstone. Semiquantitative estimates of the thickness or width of required source rock are obtained. The arguments and results are based on published statistical studies and the assumption that a degree of geometrical similarity exists among sandstones.     

Quaternary aeolianites in south‐east Australia – a conceptual linkage between marine source and terrestrial deposition

Calcareous aeolianites are an integral part of many carbonate platforms and ramps. Such limestones are particularly common in heterozoan, Late Cenozoic carbonate systems, and it has been postulated that they could contain a particularly sensitive record of their offshore source. This hypothesis is tested herein by documenting and interpreting part of the most extensive and temporally longest such system in the modern world. The deposits are a combination of extraclasts and biofragments. Extraclasts are detrital quartz, relict allochems, older Pleistocene particles and Oligocene–Miocene limestone clasts. Biofragments are penecontemporaneous coralline algae, echinoderms, small benthic foraminifera, molluscs and bryozoans. The aeolianites differ in composition from distant, open shelf sediments because they contain more mollusc fragments and many fewer bryozoans. This difference is interpreted to be due to (i) most sediment was derived from near‐shore seagrass meadows and macroalgal reefs; (ii) all sediments were modified by hydrodynamics in near‐shore and beach environments; and (iii) fragments of infaunal, beach‐dwelling bivalves were added to the sediment at the strandline. Extraclasts should be expected in older Pleistocene and Cenozoic heterozoan deposits, because the limestones are poorly lithified, largely due to the lack of meteoric cementation, and so easily eroded. Thus, cool‐water aeolianites ought to contain more extraclasts than their warm‐water, tropical cousins. Seagrasses in temperate environments are more productive than in the tropics and thus potentially might contribute many more particles to the beach and dunes than do tropical systems. Although particle breakage in the surf zone cannot be proven, herein the abundance of whole benthic foraminifera and delicate bryozoans implies that suspension and flotsam shoreward transport was an essential process. The similarity of Pleistocene aeolianites over such a long time period herein suggests that the combination of postulated sedimentological, biogenic and hydrodynamic processes could be universally important.