Beachrock as evidence of sea-level lowstand during the classical period,Parion antique city,Marmara Sea,Turkey

Results obtained from beachrock lying on the north coast of the antique city of Parion in Çanakkale province, NW Turkey, are presented based on field data, petrographic analyses, cement fabrics, and radiocarbon dating. Extending to 20?m offshore at a depth of ?2?m, the studied 50-cm thick beachrock is poorly sorted lithic sandstone. Both exposed and submerged parts are characterized by sequentially precipitated marine phreatic and vadose cements composed of micrite encrustations with micro-organism borings, pseudopeloidal aggregates of high-Mg calcites with scalenohedral habits and meniscus bridges. Radiocarbon ages point to a deposition during the classical period when the sea level was below (between ?1 and ?1.5?m) that of the present. The beachrock witnesses a granule- and pebble-dominated wide beach prior to cementation, suggesting that Parion’s fortification walls were behind the coastline during this lowstand and raises questions concerning the existence of a harbor north of the city.     

Calcite precipitation and Recrystallization fabrics—their significance in Jurassic Limestones of Europe

Many fabrics in Corallian (Upper Jurassic) carbonates in England, France and Switzerland are bigenetic, forming by solution/precipitation and recrystallization processes. Early precipitated cements are non‐ferroan, whereas those formed later are decidedly ferroan. Mossbauer spectroscopy has shown that the iron in the carbonates is largely divalent, substituting for calcium in the calcite lattice. The cements may be subdivided into those forming in an oxidizing environment, and those forming in a reducing environment. Fabric evidence indicates that a solution period separates the two cement phases. The diagenetic history is linked with the sedimentation pattern. Thus, under progressive build up of sediments into shallow‐water or supratidal conditions, the first‐phase cement probably precipitated from non‐marine, partially oxygenated vadose water. Subsequent subsidence and sedimentation resulted in the depression of partially cemented sediments into zones within the sedimentary pile conducive first to pyrite precipitation, and then to ferroan calcite precipitation. Fabrics can therefore be used to interpret the diagenetic environment of regressive sedimentary associations.     

海南岛全新世海滩岩的胶结作用与成岩环境的关系

我国海南岛及南海诸岛沿岸,广泛发育海滩岩。1980年我队赴海南岛考察现代沉积时,对海滩岩的分布、岩性特征及其与周围环境的关系进行了观察和采样。样品采自崖县鹿回头三亚湾水尾岭海蚀崖、西洲岛、小东海、东瑁岛、西瑁岛、天涯海角,乐东县莺歌海,文昌县渔业等地(图1)。有关的地质、地貌及岩性特征等,已有许多描述,对海滩岩的岩石学及成岩作用也有许多研究。本文侧重探讨海滩岩的胶结作用及与成岩环境的关系。     

海南岛全新世碳酸盐沉积及成岩作用

三亚湾珊瑚可以分为５个微相：生物骨架岩、生物屑、礁岩屑、珊瑚碎块，强烈改造的生物质，成岩作用包括同生沉积作用、胶结、藻缠结、细粒物充填，机械和化学侵蚀。排浦更新世白云岩与掘穴生物的钻孔有关，粉至中晶结构为混合水成因，峨曼更新世灰岩为砂质灰岩、角砾状灰岩，豆状灰岩。生物屑经重结晶，Ｘ（ＭｇＣＯ３）小于２％，贫铁，三亚湾潮间带海滩岩胶结物为文石和高镁方解石，见悬挂式胶结和渗滤砂。     

Methane-derived carbonate cements in barrier and beach sands of a subtropical delta complex

Highly negative δC¹³ values, ?18 to ? 40%., for carbonate cements found in Recent barrier and beach sands of the Mississippi River Delta complex strongly suggest that considerable carbon is furnished to the CaCO₃ cements by either chemical or biological oxidation of CH₄. These cemented sands are commonly found on beaches of the Chandeleur barrier island chain and other sites along the Louisiana coast where Holocene sands are rapidly transgressing over highly organic marsh deposits. Generation of CH₄ from underlying anoxic marsh sediments, followed by vertical migration and oxidation to CO₂ in the porous overlying sand, appears to be the unique set of conditions regulating this process of carbonate cementation.     

Mixed carbonates and siliciclastics in the Quaternary of southern Belize: Pleistocene turning points in reef development controlled by sea‐level change

The Belize barrier and atoll reefs represent one of the largest reef structures in the Atlantic Ocean. The southern shelf of Belize is a classic location of a modern mixed carbonate–siliciclastic system. Whereas knowledge of the Holocene deposits in the area is extensive, data on the Pleistocene system are fragmentary. Open questions include: (i) the nature of the reef foundations (carbonate versus siliciclastics); (ii) the ages of the deposits including the initiation of the barrier reef; and (iii) the response of the mixed system to sea‐level fluctuations. The results of a study of borings on the southern Belize shelf are presented here. Six, up to 105 m long borings were made to better understand the history of this important mixed system. Uranium‐series dating in the Pleistocene was not possible because of diagenetic alteration; however, lithostratigraphy, strontium isotopes and calcareous nannofossil biostratigraphy were used to constrain stratigraphic ages. Results support the contention that the Quaternary development in Belize was quite similar to that of other major barrier reefs such as the Florida Reef Tract and, further afield, the Great Barrier and the New Caledonian Barrier Reefs. All of these barrier reefs are mixed carbonate–siliciclastic systems and significant reef growth only began after the onset of high‐amplitude, eccentricity‐controlled sea‐level changes and as late as during the exceptionally long and warm marine isotope stage 11, some 400 ka. In Belize, Early Pleistocene sections at bases of borings include mollusc‐rich wackestones, rare coral packstones and marls, which were deposited under low to moderate energy conditions in a ramp setting before ca 900 ka, during the high sea‐levels of marine isotope stage 25 and possibly earlier (marine isotope stage 31 or 37). The Belize shelf was subaerially exposed for most of the mid‐Pleistocene and was dominated by siliciclastic sedimentation, possibly during marine isotope stages 24 to 12 when highstands were comparatively low. Continuous reefs at the shelf margin were developing during highstands. In the Late Pleistocene, beginning with the long and high highstand of marine isotope stage 11 (some 400 ka), the southern shelf was flooded entirely and carbonates started to dominate once more. Reefs developed on top of siliciclastic deposits on the shelf. A continuous barrier reef came into existence and largely developed on top of carbonates at the shelf margin. During Late Pleistocene lowstands, siliciclastics presumably no longer reached the shelf margin because of the topographic high of the barrier reef platform. The Quaternary Belize example may serve as a model for reconstructing ancient mixed systems in icehouse worlds, however, any extrapolations are limited by the fact that fast‐growing Scleractinian reef‐builders had not yet evolved in the Palaeozoic.     

Fabrics,facies control and diagenesis of lacustrine ooids and associated grains from the Upper Triassic,southwest England

Petrographic analysis of ooids from the Upper Triassic (Mercia Mudstone Group) of southwest England provides an opportunity to assess in detail the origins, transport pathways and diagenesis of an ancient oolite. The Clevedon Oolite is dolomitized and contains a variety of dissolved ooids (oomoulds) and associated grains. The oomoulds occur in well‐sorted, planar and cross‐stratified grainstones, packstones, sandstones and conglomerates associated with shoreface, intershoal, foreshore, beachrock and littoral strandplain deposits. The ooids grew in suspension in the shoreface zone and developed a radial aragonite microstructure. The ooids grew to 0.80 mm in diameter, after which they fractured or ceased growing. Broken grains deposited on or near mobile shoals were rapidly recoated, while other grains, deposited in less agitated, intershoal and lower foreshore areas, were micritized or microbially bound into grapestone aggregates. Locally peloids, intraclasts, quartz grains and micritized grains from intershoal areas supplied nuclei for ooids on nearby shoals. Grains deposited in foreshore areas were rapidly cemented into beachrock and reworked into conglomerates. Soon after deposition, the ooids were subjected to widespread aragonite dissolution followed by dolomitization. The lack of pre‐dolomitization calcite, together with the abundance of early (pre‐compaction) dolospar cements and fabric‐selective dolomitization of micritic fabrics, suggest aragonite dissolution by dolomitizing fluids. Copyright © 2002 John Wiley & Sons, Ltd.     

Isolated stationary carbonate platforms: the Middle Triassic (Ladinian) of the Marmolada area, Dolomites, Italy

As a result of a phase of extensional tectonics in the western Tethyan region, a horst and graben topography formed during the Middle Triassic (Ladinian) in northern Italy. Horsts were sites of shallow water carbonate sedimentation, while pelagic and volcaniclastic sediments were deposited in the grabens. Two carbonate platforms approximately 500 m thick can be distinguished in the Marmolada area of the Dolomites: the Marmolada platform proper, which covered an area of 6 km², and the Costabella platform, which extended for about 12 km in a NW-SE direction and was about 3 km across. The facies of these isolated platforms reflect the influence of storms from the SW. Windward platform margins were characterized by a marine sand belt of skeletal and aggregate grainstones with a dominant platform directed cross-stratification. The central portions of the platforms were occupied by supratidal sand cays which are made up of storm washovers. Leeward parts of the platforms are composed of shallow subtidal sand flat deposits. Laterally discontinuous reefs chiefly composed of various calcareous algae are developed at the outer margins of the platforms. Along windward margins, reefs may form a belt several hundred metres wide; along leeward margins their width is commonly reduced to some tens of metres. Foreslope talus breccias surround the platforms. Clinoform bedding showing basinward dips of 30°-40° is typical of this facies belt, which is approximately 2 km wide. Basinal sediments, only some tens of metres thick, are radiolarian micrites. Abundant sediment-gravity-flow deposits expand the basinal sequence at the toes of windward margins and were probably triggered by storm return flows. Synsedimentary faults striking both NNE-SSW and NW-SE separate the bedded platform limestones from flank deposits and reefs. They account for the stationary nature of the platforms. Neptunian dykes show preferred NNE-SSW and E-W trends. Sinistral displacements are associated with NW-SE trending faults. Depressions in the basins, filled with red, turbiditic pelagic sediments, show N-S trends and are probably compressional in origin. The structural pattern may have resulted from oblique, NW-SE oriented extension of the E-W trending Middle Triassic graben zone of the Dolomites. In the Ladinian of the Dolomites, the stationary platform type can be distinguished from a retrograding type, whereas continuously prograding platforms apparently did not develop.     

闽南、粤东海岸带沉积物的沉积学、岩石学比较研究

本文通过对海岸带海滩砂、沙丘砂、砂丘岩、海滩岩和有关近岸海底砂的沉积学,岩石学的比较研究,分析其形成环境,发现沙丘岩沉积特征和历史沙丘相似;沙丘岩和海滩岩的识别有时不是主要从岩石学而可能从沉积学中去识别。兄弟屿比西海底硬地更可能是生物排出的钙质粘液胶结。     

Computer simulation of reef growth

Light is one of the major controls on reef growth and carbonate production. The growth of present reef builders depends largely upon the amount of light available for photosynthesis. As light decreases with water depth, so does reef growth. The computer model presented extends this principle by combining two functions, one for photosynthesis and the other for the extinction of light in water. The model is used to simulate the growth of Alacran Reef, Mexico, two reefs of the Great Barrier Reef and the reefs of the windward platform of St Croix, US Virgin Islands. The model also gives an accurate simulation of the growth of fore-reef walls in Belize, in agreement with the accretion hypothesis developed for this feature.     

Animals and Mineralization of Phosphorus: Ore-Forming Mechanism of Insular Phosphorites1

Abstract Phosphorite, or guano, or insular phosphorite, commonly containing 10-35% P₂O₅, is one of the sources of phosphatic fertilizer. Taking the modern insular phosphorite on the Xisha Islands as an example, this paper discusses the ore-forming mechanism of phosphate and the important contribution made by animals to this process. The phosphorite occurs in the middle part of carbonate sand cays of coral reef surrounded by longshore sandbanks, which assumes a dish-shape. The surface of the cays is covered by unconsolidated guano. The phosphorite, yellowish brown to dark brown, is made up of thick-bedded sand and gravel cemented by collophanite; and partly replaced by carbonate apatite. The mechanism of mineralization is as follows: The average content of phosphorus in the sea water is only 0. 07 ppm, but through the sea food. chain concentration, phosphorus content may become higher. The phytoplanktons, as producers, suck up phosphorus out of sea water. The primary consumers, zooplanktons, obtain phosphorus by eating phytoplanktons, then they are followed by the second and third consumers. Sea birds living on fish, as the third consumers, concentrate and transport the phosphorus to the carbonate sand cays. Finally layers of guano are deposited under the arbores. Under the tropical climatic conditions with high temperature and plentiful rainfall, soluble matters are leached out of the guano and infiltrated into deeper horizon. In alkaline groundwater with pH greater than 7. 0, the phosphoritization takes place, bioclastics are cemented and replaced by collophanite or carbonate apatite. Finally, the phosphorus is fixed and phosphate formed.     

Carbonate cements: their regional distribution and interpretation in Mississippian limestones of southwestern New Mexico

Calcite cements in Mississippian skeletal packstones and grainstones of southwestern New Mexico are dominated by echinoderm-syntaxial, inclusion-free calcites that can be divided into four major compositional zones (from oldest to youngest: zone 1, 2, 3, 5) based mainly on varying Fe¹¹ and Mn^II contents. These compositional zones are interpreted as‘time stratigraphic’ units as indicated by petrographic evidence for age gaps between zones, and by consistency of their ages on a regional scale. As such, these cement zones can be correlated over most or all of the approximately 30,000 km² of study area, based on similarity of age, number and sequence of major zones. The inclusion-free calcite cements comprise approximately 95% of the total cements, of which the pre-Pennsylvanian zones (zones 1, 2, 3) make up about 60%, and the post-Mississippian zone 5 makes up about 40% of the total cements. These cements are interpreted as meteoric phreatic on the basis of Mn^II and Fe^II content, crystal clarity, cement morphology, substrate selectivity, low Mg content, and absence of marine and vadose characteristics. In the southern part of the study area zone 2 contains significant amounts of meteoric-marine mixing-zone phreatic cements. These mixing-zone cements are identified by their similarity in morphology, luminescence and substrate selectivity to the inclusion-free meteoric phreatic cements, but contain microdolomite inclusions indicative of former high-Mg calcites. Their restriction to the south is interpreted to have resulted from relatively long residence time of the mixing zone in the south during zone 2 precipitation. Strictly marine subtidal and beachrock cements make up less than 1% of the total cements, and meteoric vadose cements are virtually absent. Regional distribution of the pre-Pennsylvanian cement zones suggests a model of cementation during a world-wide late Mississippian eustatic regression identified by Vail & Mitchum (1976). Specifically, pre-zone 1 and zone 1 meteoric phreatic cements formed during regression within a shallow oxygenated (?) groundwater system; zone 2 formed during the later part of the regression and during stillstand in a deep-seated, more extensive flow system; zone 3 formed during subsequent transgression in a shallow groundwater system. The post-Chester, pre-Pennsylvanian unconformity resulted mainly in microkarsting and weathering. The main difference, other. than scale, between this model and those derived from diagenetic studies of Quaternary limestones is that it implies that major cementation occurred during sea-level changes in cpeiric settings, rather than only during stillstands.     

海南岛南部一地全新世生物屑灰岩的成岩作用

引言研究标本由我所碳酸岩组采自海南岛南部的一个地点。在那里,沿岸覆于原生礁之上有一套由生物骨屑(主要是珊瑚)砂、砾所组成的、已被碳酸盐胶结的岩层,其厚约3米左右(图1)。此岩层一般称为“次生礁”。它是由当时原生礁盘上的生物被海浪击碎并冲带到礁盘上沉积下来的,这里属连岛砂堤沉积,它现已完全暴露地表。次生礁在它抬升过程中,下部被海蚀形成海蚀龛。     

Diagenesis of an Upper Triassic reef complex, Wilde Kirche, Northern Calcareous Alps, Austria

The Wilde Kirche reef complex (Early-Late Rhaetian) grew as an isolated carbonate structure within the shallow Kössen Basin. At the Triassic/Jurassic boundary a single brief (c. 10–50 ka) period of subaerial exposure occurred. The preserved karst profile (70 m thick) displays a vadose zone, enhanced dissolution at a possible palaeo-watertable (5–15 m below the exposure surface), and a freshwater phreatic zone. Karst porosity was predominantly biomouldic. Primary cavities and biomoulds were enlarged and interconnected in the freshwater phreatic zone; cavity networks developed preferentially in patch reef facies. Resubmergence of the reef complex allowed minor modification of the palaeokarst surface by sea floor dissolution and Fe-Mn crust deposition on a sediment-starved passive margin. Fibrous calcite (FC). radiaxial fibrous calcite (RFC) and fascicular optic calcite (FOC) cements preserved as low Mg calcite (LMC) are abundant in primary and karst dissolution cavities. FC cement is restricted to primary porosity, particularly as a synsedimentary cement at the windward reef margin. FC, RFC and FOC contain microdolomite inclusions and show patchy non-/bright cathodoluminescence. δ¹⁸O values of non-luminescent portions (interpreted as near original) are − 1.16 to − 1.82%0 (close to the inferred δ¹⁸O of calcite precipitated from Late Triassic sea water). δ¹³C values are constant (+3 to + 2.2%0). These observations suggest FC, RFC and FOC were originally marine high Mg calcite (HMC) precipitates, and that the bulk of porosity occlusion occurred not in the karst environment but in the marine environment during and after marine transgression. The HMC to LMC transition may have occurred in contact with meteoric water only in the case of FC cement. The most altered (brightly luminescent) portions of RFC/FOC cements yield δ¹⁸O=−2.44 to − 5.8%0, suggesting HMC to LMC alteration at up to 34°C. in the shallow burial environment at depths of 180–250 m. Abundant equant cements with δ¹⁸O =−4·1 to −7.1%0 show crisp, uniform or zoned dull luminescence. They are interpreted as unaltered cements precipitated at 33–36°C at 200–290 m burial depth, from marine-derived fluids under a slightly enhanced geothermal gradient. Fluids carrying the equant cements may have induced the HMC to LMC transition in the fibrous cements.     

The fish community of a shallow tropical lagoon in Belize,Central America

Trawl collections indicate that the fish community of the Belize barrier reef lagoon is dominated numerically and in biomass by grunts (Haemulidae), especiallyHaemulon sciurus andHaemulon flavolineatum. Although the gear selected for small sizes, length frequency analysis indicated seasonality in recruitment of the dominant species of grunts. Apogonids and tetraodontiform fishes were also dominant components of the community. Most fishes collected were juveniles of species that occur as adults on the main reef, or were small species that are resident in the lagoon. Of three habitats sampled, the mangrove creek had the greatest relative abundance and biomass of fishes, followed by the seagrass bed and the sand-rubble zone. There were no significant seasonal differences in fish relative abundance or biomass. Community structure analysis indicated a uniqueness in the mangrove fish community. Diversity (H′) was high, and was due to high species richness and evenness of distribution of individuals among species. The Belize barrier reef lagoon serves as an important nursery habitat for juvenile fishes.     

贵州紫云上石炭统叶状藻礁灰岩胶结物特征

贵州紫云县猴场镇扁平村的上石炭统叶状藻礁及其周边灰岩中广泛发育大量的各类胶结物。通过对胶结物的形态、结构和阴极发光特征以及胶结物间的接触关系的研究,可以确定成岩作用的先后并识别成岩环境。浅海海底同生成岩阶段大的孔隙中形成等厚环边针状胶结物、葡萄状胶结物,小的孔隙里形成微晶胶结物。早成岩阶段形成微亮晶和斑块状亮晶方解石胶结物和放射纤维扇状胶结物,表生成岩阶段的溶蚀作用和胶结作用强烈,胶结物类型有斑块状或等粒的方解石胶结物和等厚环壁柱状胶结物,等厚环壁柱状胶结物在所有胶结物中体积是较大的。早期胶结作用使叶状藻礁灰岩孔隙度大为降低。中、晚成岩阶段,孔隙被等厚环壁刃状胶结物和晶簇或斑块状亮晶方解石所充填,有些先成的胶结物被热液改造。后生作用阶段发生的主要是构造破裂作用,其中少数裂隙被红褐色含Fe2O3微晶层和晶体粉砂及渗流豆粒充填。叶状藻礁灰岩的孔隙在晚成岩阶段前或中被胶结而之后没有创造出大且连通的孔隙,是它没能成为油气储集层的原因之一。     

Late Pliocene to Holocene platform evolution in northern Belize, and comparison with coeval deposits in southern Belize and the Bahamas

Lithostratigraphy, depositional facies architecture, and diagenesis of upper Pliocene to Holocene carbonates in northern Belize are evaluated based on a ca 290 m, continuous section of samples from a well drilled on Ambergris Caye that can be linked directly to outcrops of Pleistocene limestone, and of overlying Holocene sediments. Upper Pliocene outer‐ramp deposits are overlain unconformably by Pleistocene and Holocene reef‐rimmed platforms devoid of lowstand siliciclastics. Tectonism controlled the location of the oldest Pleistocene platform margin and coralgal barrier reef, and periodically affected deposition in the Holocene. A shallow, flat‐topped, mostly aggradational platform was maintained in the Holocene by alternating periods of highstand barrier‐reef growth and lowstand karstification, differential subsidence, and the low magnitude of accommodation space increases during highstands. Facies in Pleistocene rocks to the lee of the barrier reef include: (i) outer‐shelf coralgal sands with scattered coral patch reefs; (ii) a shoal–water transition zone comprising nearshore skeletal and oolitic sands amidst scattered islands and tidal flats; and (iii) micritic inner‐shelf deposits. Four glacio‐eustatically forced sequences are recognized in the Pleistocene section, and component subtidal cycles probably include forced cycles and autocycles. Excluding oolites, Holocene facies are similar to those in the Pleistocene and include mud‐mounds, foraminiferal sand shoals in the inner shelf, and within the interiors of Ambergris and surrounding cayes, mangrove swamps, shallow lagoons, and tidal and sea‐marginal flats. Meteoric diagenesis of Pliocene and Pleistocene rocks is indicated by variable degrees of mineralogic stabilization, generally depleted whole‐rock δ¹⁸O and δ¹³C values, and meniscus and whisker‐crystal cements. Differences in the mineralogy and geochemistry of the Pliocene and Pleistocene rocks are attributed to variable extent of meteoric alteration. Dolomitization in the Pliocene carbonates may have begun syndepositionally and continued into the marine shallow‐burial environment. Positive dolomite δ¹⁸O and δ¹³C values suggest precipitation from circulating, near‐normal marine fluids that probably were modified somewhat by methanogenesis. Sedimentologic and diagenetic attributes of the Pliocene–Pleistocene rocks in the study area are similar to those in the Bahamas with which they share a common history of sea‐level fluctuations and climate change.     

Caliche profile formation, Saldanha Bay (South Africa)

A sequence of gradational lithification events can be observed in caliche profiles, in the Saldanha Bay area (South Africa), from friable lightly cemented aeolian calcarenites or littoral shelly deposits through an intermediate semi-indurated zone to an upper strongly indurated zone (calcrete). Lightly cemented sediment fabrics exhibit bridge and meniscus cements, micritic druses and vadose compaction phenomena. The middle semi-indurated zones exhibit coated grains in which irregular borings and/or tubules with tangential acicular fibres contribute to coated grains. Random networks of acicular fibres also occur in void spaces. In fully indurated upper layers of the caliche profiles, fabrics of micriteand microspar (in voids) occur in complex brecciated macro-fabrics. The features represent changes in a sequence from the friable primary sediments to the calcretes. Fresh-water vadose flushing leaches grains and causes formation of meniscus and bridge cements and uneven druses. In the middle zone, inorganic processes are aided by the action of micro-organisms; fungi, bacteria or algae which produce tubules and irregular borings; the overall effect of which is to break down original detrital carbonate particles and enclose them in a crypto-crystalline micrite. The acicular fibres probably result from evaporation of supersaturated solution. Mechanical processes cause fracturing, which repeated many times gives complicated brecciated fabrics within the upper indurated zone.     

Submerged upper Holocene beachrock on San Salvador Island,Bahamas: implications for recent sea-level history

Sedimentological, petrographic and radiometric data from a submerged beachrock on San Salvador Island, Bahamas, provide new information about the Late Holocene sea-level history in this area.At French Bay, on the southern shore of the island, samples of beachrock collected at a depth of 1 m below low tide level yielded an average ¹⁴C age of 965 ± 60 years before present. These samples further display a well developed fenestral porosity and present an early generation of low Mg calcite meniscus cement. These features characterize intertidal and supratidal settings; they are not consistent with the present beachrock position and the reported Late Holocene sea-level history in the Bahamas. A 1.5–2m low stand of the sea about 1000 years ago would best explain the observed particularities of the French Bay beachrock.This example from San Salvador shows that the smooth trend of Late Holocene sea-level rise proposed by previous workers might be overprinted by high frequency, low amplitude fluctuations. Recognition of these fluctuations is fundamental when calculating rates of sea-level rise and evaluating the coastal response to a marine transgression. Correspondence to: P. Kindler