White Limestone Research Articles

Protecting Geoheritage in the Caribbean—Insights from Jamaica

Jamaica is the third largest island of the Greater Antilles in the Caribbean. The island consists of the Blue and John Crow Mountains in the east, the highest and largest mountain belts in Jamaica; a central plateau; and an undulating western region. The central plateau and western region are dominated by the famous Cockpit Country, which exhibits world-class karst topography. Geologically, the island is situated in a tectonically active zone and straddles the northern margin of the Caribbean Plate. Jamaica consists of several Cretaceous inliers flanked mostly by formations of the White Limestone Group and siliciclastic sediments of the Wagwater and Richmond Formations, creating spectacular geomorphological features. Although a wealth of information has been collected and published on the geology of Jamaica, there is still the issue of protection of natural sites and sites of scientific interest. These sites are under constant threat from development and lack of custodial management. Jamaica is at risk of losing valuable geological data simply because the appropriate attention is not being paid to significant sites. This paper describes strategies used in cultural heritage, natural parks and conservation programmes. The purpose is to develop a set of criteria that can be used to begin the process of protecting significant geological localities. The paper captures the concept of sustainable development, geoconservation and geodiversity for education, public awareness and disaster management (mitigation, planning, risk reduction).

Variety of Black and White Limestone Tesserae Used in Ancient Mosaics in Slovenia

This study concerns the microfacies characterization of white and black limestone tesserae from selected Roman floor mosaics in Slovenia, with the aim of defining their provenance. We investigated 42 tesserae from 15 different mosaics from the archaeological sites of Ljubljana, Izola, Mošnje, Ptuj, Črnomelj and Šentpavel, dated from the first century bc to the fifth century ad. Among the studied tesserae, 13 different microfacies were identified: eight black and five white. The most common were mudstones with ostracods (65% of black tesserae) and wacke‐packstones with miliolids (85% of white tesserae). The majority of the identified facies can be found in the Cretaceous successions of the Dinaric Carbonate Platform in south‐western Slovenia, north‐eastern Italy and south‐eastern Croatia, suggesting a regional or imported origin of the tesserae.

Professor Ron K. Pickerill and the genesis of ichnology in the Antilles (Jamaica and Carriacou)

Antillean ichnology was essentially a blank book when Ron Pickerill of the University of New Brunswick, Fredericton, made his first research visit to Jamaica in February 1990. Ron’s first Jamaican trace-fossil research team worked initially on the Paleogene Richmond Formation, a flysch succession. Subsequent fieldwork examined the diverse sedimentary formations of the Neogene Coastal Group. Ron’s encyclopaedic knowledge of ichnotaxonomy and his enthusiasm for fieldwork led the team in many directions. Investigations were integrated with new studies of the island’s sedimentology and paleontology. For example, the description of the ichnology and sedimentology of the Upper Pliocene Bowden Formation, including the internationally famous Bowden shell bed, was part of a much wider study. The case-hardened rocks of the White Limestone Group discouraged detailed study until Donovan Blissett attacked the diverse ichnobiota of these user-unfriendly rocks for his doctorate under Ron’s supervision at the University of New Brunswick. Carriacou in the Grenadines was the other island to receive detailed examination in terms of its ichnofauna by Ron and his co-workers. The east coast of this small island provides a near-continuous exposure of the deep water succession of the Grand Bay Formation. Deeper-water burrows and borings in allochthonous bioclasts derived from the shallow shelf provide ichnological contrast in this formation.

Development of high-efficiency bifacial photovoltaic module and simulation method for its power generation

We have been producing the bifacial module, the HIT® Double, since 2000. This module was the first to be released in the world.) We have since been developing high efficiency bifacial modules. We released a new bifacial photovoltaic (PV) module in 2013. It has a conversion efficiency of 16.0% in spite of having a light-through area of 8% within the total module area, and the temperature coefficient of the output power is quite good at −0.29%/°C. It passed various environmental tests that are much stricter than the industrial standard. Our field test showed the effectiveness of vertically installing the bifacial module, especially when installed on ground that highly reflects light such as snow or white limestone. We developed an original simulation method to accurately estimate the energy production of the bifacial module. A simulation accuracy of about 3.7% was confirmed through practical test results at our field test site in Niigata Prefecture, Japan.

The stones of the statuary of the Egyptian Museum of Torino (Italy): geologic and petrographic characterization

A geologic and petrographic study was performed on a rich collection of statues made of stone exposed at the statuary of the Egyptian Museum of Turin (NW Italy) to enhance the value of this artistic heritage and set the basis for its best conservation. Magmatic and sedimentary rocks were recognized. Magmatic rocks with an intrusive origin are the most represented and include two main varieties: Red Granite, consisting of a sieno-granite with porphyritic texture and pink to red K-feldspars, and Black Granite, which includes granodiorite, quartz diorite and tonalite lithotypes, whose colour ranges from grey to almost black. These magmatic rocks belong to the Arabian–Nubian shield, and the historical quarries are located near Aswan. The sedimentary rocks are represented by Cenozoic white limestones and red sandstones and Cretaceous dark-yellow Nubian sandstones. Finally, we note the occurrence of the so-called Bekhen Stone, originally attributed to a green-black metagreywacke belonging to the Hammamat series of late Precambrian age, outcropping in the central sector of the Eastern Desert, and re-interpreted here as a massive dark-green sandstone. This paper provides a scientific classification of the artefacts exposed in the statuary rooms based on the employed materials and contributes to the enhancement of the valuable collection of stone artefacts preserved in one of the leading ancient Egyptian Museums in the world.

Discussion of Jamaican Cenozoic ichnology: review and prospectus: (v. 50, pp. 364–382)

We make two comments on the paper ‘Jamaican Cenozoic ichnology: review and prospectus’ by Donovan et al. (2015). Based on biostratigraphy and new radiometric dates, we recommend the separation of the Richmond Formation (deposited in the Wagwater Graben and onlapping onto the edges of the Clarendon Block and Blue Mountains Block) and the Moore Town Formation (deposited in the John Crow Mountain Graben) which are of early Eocene and early Paleocene age, respectively. The ichnofossils of the Scolicia ichnocoenesis are different in the two basins. We also point out that extensive borings recorded from the late Eocene Somerset Formation of the White Limestone Group most probably came from the late Oligocene Walderston Formation. Copyright © 2015 John Wiley & Sons, Ltd.

Reply to discussion of Jamaican cenozoic ichnology: review and prospectus: (v. 50, p. 364–382)

Mitchell and Ramsook comment on the lithostratigraphic assignment of Jamaican Cenozoic ichnofossils discussed in Donovan et al. They argue that the Paleogene Richmond Formation should be subdivided to produce a ‘Moore Town formation’ in eastern Jamaica, but the latter remains undefined as a lithostratigraphic unit and no new lithostratigraphic evidence is produced to support their supposition. Further, their use of a flawed table of trace fossil distributions does not support their thesis. The distribution of trace fossils in the White Limestone Group presented by Donovan et al. follows the lithostratigraphic scheme that was current at the time that the research was originally undertaken in the early 2000s. Yet, whatever lithostratigraphic scheme is utilised for the island, it is apparent that the more accurate data is provided by the biostratigraphy of the larger benthic foraminifers. Copyright © 2015 John Wiley & Sons, Ltd.

A Postclassic Maya mass grave from Zacpetén, Guatemala

Here we present a bioarchaeological analysis of a Postclassic (ca. a.d. 950–1524) Maya mass grave from the site of Zacpetén in northern Guatemala. Osteological and spatial analyses (including a Ripley’s K function) found evidence of cutting, drilling, and grinding of long bones and teeth as well as the intentional removal and manipulation of skeletal elements based on the left or right sides of the body. The remains were enveloped in layers of cut blocks and fist-sized chunks of white limestone and were placed in a depression on the western side of the ceremonial core of the site. The western orientation of the depression was explicitly associated with the underworld in contrast with the temple on the eastern side of the ceremonial core. The grave was the product of exhumation and violation of enemies’ bodies, sacrifice, or the burial of war dead (or some combination thereof) and was created when the Kowoj group emerged as a political force in the Petén lakes region. It served to symbolically rupture the past inhabitants’ links to the site and to create an enduring symbol of their defeat.

Lithology, fauna and environmental conditions of the Late Pleistocene raised reefal limestone of the Jeddah coastal plain, Saudi Arabia

The upper successions of the raised reefal limestone of Jeddah coastal plain, especially at Obhur area, were investigated through three temporary exposed geologic sections such as south and northeast Obhur and Al Salam Street. Uranium-series age datings of these successions indicated that their topmost parts were mostly deposited during the last interglacial marine isotope stage 5e (MIS 5e). Lithological–faunal analyses and field observations allowed the division of these successions into two distinct layers: white limestone (lower) and brown shell-rich calcareous clay (upper). The lower layer is enriched with in situ coral boulders of Porites sp. and faviids, as well as with the foraminifers Amphistegina sp., indicating deposition near fore reef and reef crest environments. The upper layer is enriched with molluscs, echinoids, branched (and dwarfed faviids) corals, and the foraminifers Elphidium striatopunctatum and Challengerella bradyi, indicating deposition in back reef, lagoonal environments. The boundary between these two layers is very sharp and irregular, suggesting that the transition from the fore reef to lagoonal conditions was very rapid and catastrophe on coral reef ecosystem due likely to sea-level changes accompanied with warming and increased water runoff. The upper surface of the shell-rich calcareous layer seems to be truncated, but its microfossils could indicate that it was deposited when the sea level was higher than the present mean sea level (MSL) by at least 7 m.

Porosity of Avanah Formation and its Stratigraphical Distribution in Selected Wells of Kirkuk Oil Field

The dolomitic and recrystallized carbonates of Avanah Formation (Middle - Late Eocene) successions are characterized by relative high porosity and permeability. These successions, in the selected wells (K-432,K-117,K-149,K-319,K-339), start with brown-white, fractured, rigid and porous at lower dolomitic unit, overlain by dense-fractured, high porous, relatively rigid and brown dolomitic limestone; and finally ending by low-fractured, moderately rigid and porous white limestone. The rocks of the formation are rich in sieve mosaic dolomitic texture with lesser suture, spotted, fogged and poikilotopic textures, in addition to another diagenetic features, which are formed due to recrystallization, cementation, dissolution, physical compaction, dedolomitization and micritization. It is obvious that the dolomitization and dissolution have played a positive role in improving the porosity of specified rock units. On the contrary of the upper unit, both lower and middle units are characterized by their high porosity (vuggy, intercrystalline, fractured and moldic), whereas the porosity of the upper unit is restricted to fracture and intergranular types. By merging density and neutron logs for calculating the total and effective porosity of the successions, it is revealed that they are of high porosity (2-30%) which is coincident with the results of the plotted density - neutron log values on (b-ØN) chart. It is believed that the relative domination of diagenetic porosity diagnosed in the rocks of lower and middle successions of the formation, and its observed association with fractured porosity (Hybrid-2) on the other hand have improved the porosity and permeability of these rocks making them efficient to store and produce hydrocarbons.

Jamaican Cenozoic ichnology: review and prospectus

Jamaica has the most diverse record of Cenozoic trace fossils of any of the Antillean islands, with over 100 ichnospecies divided among more than 50 ichnogenera. Trace fossils have been identified from both shallow‐ and deep‐water deposits in most major lithostratigraphic divisions, namely the Paleogene Richmond Formation (Wagwater Group), the mid‐Cenozoic White Limestone Group and the Neogene Coastal Group. Persistent ichnogenera in these palaeoenvironments include the burrows Palaeophycus Hall, Planolites Nicholson, Taenidium Heer and Thalassinoides Ehrenberg (deeper water), and the borings/microborings Entobia Bronn, Gastrochaenolites Leymerie and Oichnus Bromley (shallow water). Differences in diversity of ichnotaxa between formations can, in part, be due to differences in lithofacies and absolute water depth. This is recognized in the differences in deeper water lithofacies between the Richmond Formation (siliciclastic turbidites), White Limestone Group (chalks), Lower Coastal Group (submarine mass flow deposits) and Upper Coastal Group (deep fore reef). Intervals and lithofacies still awaiting detailed investigation include Pleistocene red beds and fore‐reef, Pliocene raised reef and shallow siliciclastic shelf, and most of the varied palaeoenvironments represented by the Eocene Yellow Limestone Group. Only crocodile coprolites (Eocene) are attributable to vertebrates; algal microborings apart, the only plant traces are Pleistocene root casts that await description. Copyright © 2014 John Wiley & Sons, Ltd.

Petrographic and geochemical features of sinkhole-filling deposits associated with an erosional unconformity on Grand Cayman

On Grand Cayman, exposures of dolostones belonging to the Cayman Formation (Miocene) represent an erosional unconformity that has been developing since the late Pliocene (~3.6Ma). Sinkholes that developed during this time have remained open or become partly to fully filled with various combinations of rootcrete, breccias, loose limestone and dolostone lithoclasts, and white, red and orange limestones. These sinkhole-filling deposits have different geochemical attributes to the Neogene and Pleistocene marine carbonates that form the bedrock of the island. The deposits in the sinkholes formed in response to the variations of sea level, climate, exposure, and vegetation that developed during the period when the erosional unconformity was developing.The rootcrete, oncoids, red and orange limestones are terrestrial in origin, whereas the limestone and dolostone lithoclasts and white limestones are derived from marine deposits. On the erosional unconformity, intense root activity led to the formation of rootcrete and terrestrial oncoids but also selectively blackening reworked marine carbonates. The red and orange limestone matrices, which formed under more arid conditions, contrast with the other sinkhole-filling deposits that formed during periods when the climate was semi-arid to humid. The distinctive REE signatures of the sinkhole-filling deposits, which are different from those of the bedrock limestones and dolostones, can probably be attributed to trace amount of terra rossa and/or airborne Saharan-derived dust that are present in those deposits.

EVIDENCE FOR LADINIAN (MIDDLE TRIASSIC) PLATFORM PROGRADATION IN THE GYULAKESZI AREA, TAPOLCA BASIN, WESTERN HUNGARY: MICROFACIES ANALYSIS AND BIOSTRATIGRAPHY

A shallowing-upward carbonate sequence was studied from the outcrop at Gyulakeszi, Tapolca Basin (western Hungary), and it is interpreted as a Middle Triassic ( Curionii or younger) platform progradation. Two lithostratigraphic units are distinguished. Microfacies analysis and micropaleontological investigation conducted on the red nodular, cherty limestone (Vaszoly and Buchenstein formations) suggest that the lower unit was deposited during the Reitzi and the Secedensis ammonoid zones. The overlying white platform limestone (upper unit) is typical of a prograding platform and includes gravity-driven deposits at the base followed by periplatform facies deposited in shallow marine warm waters around the fair-weather wave base. The section at Gyulakeszi was unaffected by fabric-destructive dolomitization, which is uncharacteristic of similar platform facies in the Balaton Highland. Isopachous and radiaxial fibrous calcite cement found in the grainstone and boundstone facies are indicative of early lithification and diagenesis in the marine phreatic zone. “Evinospongiae”-type cement is described for the first time from the Balaton Highland and it is similar to the outer platform cements published previously from the Alps (Italy and Austria). The progradation could have advanced over the pelagic limestones as early as the Curionii zone, which is an undocumented event in the Veszprem Plateau. Similar event, however, is well known from the Western Dolomites, where aggradation was followed by intense progradation during the Gredleri and Archelaus ammonoid zones. The length of this progradation event at Gyulakeszi, however, is ambiguous since proven Ladinian (Longobardian) rocks are not exposed in the study area and were not penetrated by boreholes in the Tapolca Basin.

Quasi-flexural folding of pseudo-bedding

The disharmonic outcrop-scale folds and associated structures in a 300-m-thick Cretaceous limestone formation in the Pindos Group exposed on Mount Lykaion (Arcadia, Greece) can be understood only in the context of superposed pre-tectonic and tectonic mass-transfer dissolution creep. Though the structures described may seem unusual, they are undoubtedly abundant in strongly deformed pseudo-bedded limestone formations. In this example the Thick White Limestone Beds (TWLB) formation displays pervasive flaggy pseudo-bedding, which is a diagenetic stylolitic layering resulting from pressure dissolution. The mass-transfer dissolution creep that produced the diagenetic stylolitic surfaces was achieved during gravitational loading accompanying burial, compaction, and lithification, and was driven by high stress concentrations at grain contacts. The diagenetic stylolitic surfaces are lined with insoluble residue and commonly are marked by interlocking stylolite teeth oriented perpendicular to the pseudo-bedding. At the outcrop scale, individual pseudo-beds display significant thickness variability. Moreover, the individual pseudo-beds not uncommonly wedge out and disappear laterally over very short distances. Along with all the Pindos Group strata, the TWLB formation was profoundly shortened in the Late Cretaceous and early Tertiary as a result of inversion tectonics. The Pindos Group limestone-dominated formations underlying and overlying TWLB readily accommodated flexural-slip folding, for these formations are marked by optimum mechanical stratigraphy, ubiquitous thin bedding, and pervasive bedding-plane slip surfaces. For the TWLB formation, however, strain accommodation by flexural-slip kinematics was spotty and inefficient, primarily because individual diagenetic stylolite surfaces are by no means planar or smoothly curviplanar; they tip out over short distances; and their interlocking stylolite teeth create elevated frictional resistance to layer-parallel slip. These factors, plus the apparent ease with which the limestone pseudo-beds deform by tectonically induced mass-transfer dissolution creep, were responsible for the distinctive structures observed in outcrop. These include indentation structures, where a part of one fold limb indents into the other, or where the hanging wall of a small thrust indents into its footwall, or where the limbs of a common anticline or syncline migrate toward one another by pressure dissolution removal of the axial-trace region. In terms of the overall progressive deformation, tectonically driven layer-parallel shortening of pseudo-beds first resulted in tectonic stylolites perpendicular to pseudo-bedding, with teeth parallel to pseudo-bedding. This was superseded at the mesoscopic scale by a layer-parallel shortening achieved by buckling of pseudo-beds, with loci of buckling and incipient buckling geometries influenced primarily by pseudo-bed thickness (and variations in same), wedge-outs of pseudo-beds, and the mechanical properties of the pseudo-beds. In some cases shortening and tightening of buckle folds involved flexural-slip kinematics, accommodated in part by slip or shear along clayey insoluble residue at pseudo-bed contacts. Where diagenetic stylolite surfaces abruptly tipped out, or where friction along them was excessively high, the slip deficit (and thus shortening deficit) was replaced by mass interpenetration of pseudo-beds, stylo-faulting, stylo-duplexing, and other forms of mass-transfer dissolution creep. Slip toward the tip lines of wedge-outs even may have produced end loading that, in turn, generated adjacent localized buckle folds. The properties of the folds and associated structures in the TWLB formation are introduced here as a new category of quasi-flexural folds in the Donath and Parker (1964) classification.

Stratigraphy of the White Limestone of Jamaica

Abstract The lithostratigraphy of the White Limestone Group (Eocene-Miocene) of Jamaica is revised based on geological mapping across the northern part of the Clarendon block. Eight shallow-water formations are recognised which are from base to top: Healthy Hill Formation (new name): predominantly white grainstones; Troy Formation: recrystallized and dolomitized limestones; Swanswick Formation: white grainstones; Claremont Formation: pale micritic limestones (locally recrystallized and dolomitized); Somerset Formation: pink grainstones and packstones with large white globular foraminifers; Walderston Formation: pink grainstones; Browns Town Formation: white packstones and wackestones with abundant large lens shaped foraminifers and abundant corals; and Newport Formation: pale wakestones and carbonate mudstones. The facies and their foraminifer assemblages are interpreted in terms of sequence stratigraphy.

From black-and-white to colour in the Silurian

Ironstones and iron-rich limestones regularly occur as components of time-specific intervals of the Palaeozoic as well as in younger times (Brett et al., 2012--this issue). Silurian sediments deposited at high latitudes along the peri-Gondwana border are characterized by black and white limestone and graptolitic shale sequences. Those in the Carnic Alps (southern Austria) additionally contain colourful pink to red limestones and ironstones. Laminated structures such as the (ferruginous)-coatings around skeletal fragments (mostly trilobites and some cephalopods and echinoderms) and stromatolitic features along discontinuity surfaces display dark red, green, white and brownish colours due to the presence of goethite, magnetite, hematite, chamosite, calcite and subordinate apatite. Confocal laser Raman microscopy and complementary microscopic analysis of these ferruginous laminated structures document the presence of carbonaceous matter associated with fossilized microbial structures in the form of stromatolites, filaments and coccoids, suggesting a microbial role in the colouring of the Silurian world of the Carnic Alps. Iron concentrations up to 30× that of matrix and surrounding non-ferruginous rocks suggest blooms of iron microbe activity in response to the time-specific occurrence of chemically charged sea water during global biotic events.

Durability of mortars of white cement against sulfate attack in elevated temperatures

In this study, white cement CEM I-32,5 & white limestone cement CEM II-A/LL, with 15% limestone substitution, were investigated. Mortars were made from these types of cement and the durability of these mortars against sulfate attack as well as the effect of temperature (50°C) were investigated.During the experiment, the mortar samples were being observed visually on a regular basis using the Heine Delta 20® LED Illuminated Loupe 10× device. After a period of 90days, the mortar samples’ compressive strength was determined and the deterioration products which affected the durability were identified. The identification of the deterioration products was made through means of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM-EDAX), Thermogravimetry (TG), Infra-Red Spectroscopy (FT-IR) and Mercury Porosimetry (MP).The results of this study clearly displayed that the rate of sulfate attack to the cement with limestone substitution was lower compared to that of pure cement. Furthermore, it was shown that this type of cement is three times more durable than pure cement of the same category. It was also identified via different methods of analysis that the cause of the deterioration was the development of microcrystalline ettringite which caused microcracks and degradation of the specimens.In conclusion, it is shown that in the case of same class cement with limestone substitution, such a microstructure is developed which does not allow the penetration by sulfate ions. This is demonstrated through the higher resistance of this specific mortar despite the adverse conditions in which these mortars were exposed to.

Reliability of using nondestructive tests to estimate compressive strength of building stones and bricks

This study aims to investigate the relationships between Schmidt hardness rebound number (RN) and ultrasonic pulse velocity (UPV) versus compressive strength (fc) of stones and bricks. Four types of rocks (marble, pink lime stone, white lime stone and basalt) and two types of burned bricks and lime-sand bricks were studied. Linear and non-linear models were proposed. High correlations were found between RN and UPV versus compressive strength. Validation of proposed models was assessed using other specimens for each material. Linear models for each material showed good correlations than non-linear models. General model between RN and compressive strength of tested stones and bricks showed a high correlation with regression coefficient R2 value of 0.94. Estimation of compressive strength for the studied stones and bricks using their rebound number and ultrasonic pulse velocity in a combined method was generally more reliable than using rebound number or ultrasonic pulse velocity only.

Application Research of White Mud in 660 MW Unit FGD System

White mud is generally known as the residue of soda ash production by ammonia-soda process. The treatment of it has been one problem in soda ash industry due to the large amount of production, strong alkalinity and corrosiveness. In China, the treatment of white mud is stacking currently, which not only occupying land but also causing environment pollution. The main composition of it is the calcium carbonate. If white mud replaces the limestone as the desulfurization agent in wet Flue Gas Desulfurization (W-FGD) system, it can attain the goal of treating the waste with another, achieve the circular economy between enterprises, and reduce the desulfurization cost significantly. In this paper, the research of white mud in 660 MW Unit W-FGD systems was investigated. Study shows that the properties of white mud and limestone are significantly different. Because of smaller particle size and active MgO, the alkaline and reaction activity of white mud are better than that of limestone, results to higher desulfurization rate and lower running cost. However, the purity of white mud is lower because of CaSO4, Cl-, and other impurities, so the dewatering system of gypsum needs to increase output by about 17%; the output of the slurry feed system needs to be increased by about 30%; the discharge capacity of wastewater needs to be increased by about 23 t/h.

Rhodoliths, uniformitarianism, and Darwin: Pleistocene and Recent carbonate deposits in the Cape Verde and Canary archipelagos

Visiting “St. Jago” (Santiago) in the Cape Verde Islands in 1832 and again in 1836 aboard HMS Beagle, Charles Darwin was the first to trace and describe the tri-part sequence of white limestone and sandstone beds stratigraphically located between two levels of basalt exposed almost uninterrupted for 10km along coastal cliffs. The Pleistocene carbonate sediments dominated by rhodoliths and rhodolith debris accumulated on a basalt shelf and subsequently became buried by subaerial and submarine basalt on the southeast coastline of Santiago. The main goal of this contribution is to re-examine Darwin's stratigraphic sequence. The secondary goal is to provide a general taphonomical model based on the observation of Recent rhodolith deposits for evaluation of fossil rhodolith assemblages. Environmental uniformitarianism is employed to understand the depositional history of the southern Santiago rhodolith-bearing strata. The mixed clastic-carbonate sequence includes a basalt-derived basal conglomerate with an intertidal to shallow subtidal fossil assemblage mainly denoted by limpets and oysters. Upper layers typically demonstrate swaley and hummocky cross stratification incorporating rhodolith debris further modified by bioturbation. Pillow basalts from 10 to 18m in thickness succeeded by subaerial flows imply swift burial of the carbonate succession under equivalent water depths. The calcareous nannofossil assemblage was investigated to more precisely date the deposits. Darwin's paleoshore is reinterpreted to represent two different transgressions occurring between approximately 1.1 and 0.7Ma. Taphonomic grades from whole rhodoliths to finely crushed rhodolith debris observed under present-day conditions on Maio (Cape Verde Islands) and Fuerteventura (Canary Islands) were used to model rhodolith preservation and to constrain the depositional settings to which rhodoliths may be transported from the offshore banks where they naturally thrive. Coastward transport of rhodoliths commonly ends with deposition in subtidal storm beds, tidal pools, and platform over-wash deposits, as well as beach, berm, hurricane, tsunami, and coastal dune deposits.