Literatura científica selecionada sobre o tema "Coral reef core"

A quantitative study was made of the orientation of corals and stromatoporoids in reef core, flank, and interreef rocks representing three geological periods at eight sites, including the Florida Keys (Pleistocene), Ridgemount, Ontario (Devonian), and Pekin, New York, Maumee and Rockford, Ohio, and Bluffton and Delphi, Indiana (Silurian). Orientation, width, and height were measured for each fossil as seen in outcrop.Fossils in Pleistocene and Silurian reef core facies have pronounced upward orientation, suggesting that most fossils are in growth location, or that the reefs were moved to their present location without appreciable tilting. Silurian distal flank facies have approximately random coral orientations, while the proximal (near-core) Silurian flank facies at Rockford has coral orientations with some upward bias. Coral width is greater than or equal to coral height (on outcrop) for 79% of the corals at all flank sites, and for 80% of the corals at the interreef site, an indicator of transport when taken with orientation data. This study permits reef facies differentiation and illustrates that fossil orientation is a useful technique for studying reefs.

Abstract. Assemblages of corals characterise specific reef biozones and the environmental conditions that change spatially across a reef and with depth. Drill cores through fossil reefs record the time and depth distribution of assemblages, which captures a partial history of the vertical growth response of reefs to changing palaeoenvironmental conditions. The effects of environmental factors on reef growth are well understood on ecological timescales but are poorly constrained at centennial to geological timescales. pyReef-Core is a stratigraphic forward model designed to solve the problem of unobservable environmental processes controlling vertical reef development by simulating the physical, biological and sedimentological processes that determine vertical assemblage changes in drill cores. It models the stratigraphic development of coral reefs at centennial to millennial timescales under environmental forcing conditions including accommodation (relative sea-level upward growth), oceanic variability (flow speed, nutrients, pH and temperature), sediment input and tectonics. It also simulates competitive coral assemblage interactions using the generalised Lotka–Volterra system of equations (GLVEs) and can be used to infer the influence of environmental conditions on the zonation and vertical accretion and stratigraphic succession of coral assemblages over decadal timescales and greater. The tool can quantitatively test carbonate platform development under the influence of ecological and environmental processes and efficiently interpret vertical growth and karstification patterns observed in drill cores. We provide two realistic case studies illustrating the basic capabilities of the model and use it to reconstruct (1) the Holocene history (from 8500 years to present) of coral community responses to environmental changes and (2) the evolution of an idealised coral reef core since the last interglacial (from 140 000 years to present) under the influence of sea-level change, subsidence and karstification. We find that the model reproduces the details of the formation of existing coral reef stratigraphic sequences both in terms of assemblages succession, accretion rates and depositional thicknesses. It can be applied to estimate the impact of changing environmental conditions on growth rates and patterns under many different settings and initial conditions.

Use of coral skeletons to determine growth histories of reefs situated in warm, clear tropical waters is well established. Recently, however, there has been increasing awareness of the significance of reefs occurring in environments that are considered as marginal for coral growth, such as turbid inshore settings characterized by episodes of elevated turbidity, low light penetration, and periodic sediment burial. While these conditions are generally considered as limiting for coral growth, coral reefs in these settings can exhibit high live coral cover and species diversity, and thus can be both ecologically and geologically significant. Turbid-zone reefs are also commonly concentrated along eroding shorelines with many analogues to erosional shorelines developed during the Holocene transgression. A growing number of studies of these previously undocumented reefs reveal that the reef deposits are detrital in nature, comprising a framework dominated by reef rubble and coral clasts and set within a fine-grained terrigenous sediment matrix. In addition to the recognized effects of diagenesis or algal encrustations on the radiocarbon signature of coral samples, episodic high-energy events may rework sediments and can result in age reversals in the same stratigraphic unit. As in other reef settings, the possibility of such reworking can complicate the reconstruction of turbid-zone reef growth chronologies. In order to test the accuracy of dating coral clasts for developing growth histories of these reef deposits, 5 replicate samples from 5 separate coral clasts were taken from 2 sedimentary units in a core collected from Paluma Shoals, an inshore turbid-zone reef located in Halifax Bay, central Great Barrier Reef, Australia. Results show that where care is taken to screen the clasts for skeletal preservation, primary mineralogical structures, and δ13C values indicative of marine carbonate, then reliable 14C dates can be recovered from individual turbid reef coral samples. In addition, the results show that these individual clasts were deposited coevally.

A new decapod crustacean assemblage associated with late Eocene coral reef deposits in northeast Spain (southern Pyrenees) is recorded; it includes Gemmellarocarcinus riglosensis sp. nov., Daira corallina sp. nov., Lobogalenopsis joei sp. nov., Liopsalis cf. anodon (Bittner, 1875) and Galenopsis crassifrons A. Milne- Edwards, 1865. The genera Gemmellarocarcinus, Daira and Lobogalenopsis are here recorded for the first time from Eocene strata of the Iberian Peninsula, extending their palaeobiogeographical distribution. Detailed sampling from three different coral reef facies within the La Peña buildup, here referred to as branching, tabular and massive, suggest that the core of the reef, which was dominated by branching corals, hosted the highest diversity and abundance of decapod crustaceans. Daira corallina sp. nov. predominated in the branching corals facies, while G. crassiforns was the most abundant taxon within the tabular coral facies and carpiliids showed preferences for environments with massive corals. Thus, this constitutes a good example of primary ecological zonation among decapod crustaceans within a discrete reef.

We review the evidence for bio-regulation by coral reefs of local climate through stress-induced emissions of aerosol precursors, such as dimethylsulfide. This is an issue that goes to the core of the coral ecosystem’s ability to maintain homeostasis in the face of increasing climate change impacts and other anthropogenic pressures. We examine this through an analysis of data on aerosol emissions by corals of the Great Barrier Reef, Australia. We focus on the relationship with local stressors, such as surface irradiance levels and sea surface temperature, both before and after notable coral bleaching events. We conclude that coral reefs may be able to regulate their exposure to environmental stressors through modification of the optical properties of the atmosphere, however this ability may be impaired as climate change intensifies.

Abstract. Tropical cyclones (TCs) and sea level rise (SLR) cause major problems including beach erosion, saltwater intrusion into groundwater, and damage to infrastructure in coastal areas. The magnitude and extent of damage is predicted to increase as a consequence of future climate change and local factors. Upward reef growth has attracted attention for its role as a natural breakwater, reducing the risks of natural disasters to coastal communities. However, projections of change in the risk to coastal reefs under conditions of intensified TCs and SLR are poorly quantified. In this study we projected the wave height and water level on Melekeok reef in the Palau Islands by 2100, based on wave simulations under intensified TCs (significant wave height at the outer ocean: SWHo = 8.7–11.0 m; significant wave period at the outer ocean: SWPo = 13–15 s) and SLR (0.24–0.98 m). To understand effects of upward reef growth on the reduction of the wave height and water level, the simulation was conducted for two reef condition scenarios: a degraded reef and a healthy reef. Moreover, analyses of reef growth based on a drilled core provided an assessment of the coral community and rate of reef production necessary to reduce the risk from TCs and SLR on the coastal areas. According to our calculations under intensified TCs and SLR by 2100, significant wave heights at the reef flat (SWHr) will increase from 1.05–1.24 m at present to 2.14 m if reefs are degraded. Similarly, by 2100 the water level at the shoreline (WLs) will increase from 0.86–2.10 m at present to 1.19–3.45 m if reefs are degraded. These predicted changes will probably cause beach erosion, saltwater intrusion into groundwater, and damage to infrastructure, because the coastal village is located at ∼ 3 m above the present mean sea level. These findings imply that even if the SWHr is decreased by only 0.1 m by upward reef growth, it will probably reduce the risks of costal damages. Our results showed that a healthy reef will reduce a maximum of 0.44 m of the SWHr. According to analysis of drilled core, corymbose Acropora corals will be key to reducing the risks, and 2.6–5.8 kg CaCO3 m−2 yr−1, equivalent to > 8 % of coral cover, will be required to keep a healthy reef by 2100. This study highlights that the maintaining reef growth (as a function of coral cover) in the future is effective in reducing the risk of coastal damage arising from wave action. Although the present study focuses on Melekeok fringing reef, many coral reefs are in the same situation under conditions of intensified TCs and SLR, and therefore the results of this study are applicable to other reefs. These researches are critical in guiding policy development directed at disaster prevention for small island nations and for developing and developed countries.

In 1917, Alfred Mayor surveyed a 270 m transect on a reef flat on American Samoa. Eleven surveys were conducted on the transect from 1917 to 2019. The coral community on the reef crest was resilient over the century, occasionally being seriously damaged but always recovering rapidly. In contrast, the originally most dense coral community on the reef flat has been steadily deteriorating throughout the century. Resilience of coral communities in regions of high wave energy on the reef crests was associated with the important binding function of the crustose coralline alga (CCA) Porolithon onkodes. Successful coral recruits were found on CCA 94% of the time, yet living coral cover correlated negatively with CCA cover as they became alternative winners in competition. Mayor drilled a core from the transect on the surface to the basalt base of the reef 48 m below. Communities on Aua reef were dominated by scleractinians through the Holocene, while cores on another transect 2 km away showed the reef was occupied by alcyonaceans of the genus Sinularia, which built the massive reef with spiculite to the basalt base 37 m below. Despite periods of sea levels rising 9 to 15 times the rate of reef accretion, the reefs never drowned. The consistency of scleractinians on Aua reef and Sinularia on Utulei Reef 2 km away during the Holocene was because the shape of the bay allowed more water motion on Aua reef. After 10700 yr of reef building by octocorals, coastal construction terminated this spiculite-reef development.

The continuity of coral reef ecosystem highly depends on the new coral larvae recruitment process. Hence, the information regarding distribution, the abundance of corals, and its relation to other variables are highly important in that ecosystem management. Research was conducted at nine stations represented each zone at the conservation area of Kapoposang Marine Tourism Park (TWP Kapoposang). This research aims at seeking for spatial variations of the abundance of coral recruitment at three primary zones monitored (core zone, sustainable fishing zone and utilization zone) and we further identified its relations with spatial variation of herbivorous fishes abundance and coral cover’s condition at those zones. The coral recruitment observation employed transect quadrat sampling method with size of 1x1 meter and 10 times repetition at a similar depth, and the coral recruitment abundance measurement in natural habitat based on the amounts of juvenile corals has been defined as coral colony with size of ≤10 cm. Overall, this research has found 534 coral juveniles consisted of 19 genera and 7 families, and the average of juvenile coral density stood at 5.34±4.45 SE.m-2. The coral reef recruitment category at TWP Kapoposang could be classified as high and its abundance spatial distribution showed no significant differences between each zone, as well as not influenced by either herbivorous fish abundance variable or the percentage of live coral cover.

Despite suggestions to the contrary by Norman Newell, in 1971, the presence of in-place, interlocking framework remains primary among the list of criteria used to recognize “true reefs” in the rock record. This is a logical outgrowth of observations made in modern systems, emphasizing 1) high carbonate-production rates of modern corals, 2) their commonly upright and interlocking architecture, and 3) the abundance and diversity of closely packed organisms on the surface of many modern reefs.Applying a framework-dominated model to ancient reefs, however, has led to repeated frustration and the assumption that the problem is by and large related to the changing nature of reefs through time. Our present attempt to apply uniformitarianism to modern reefs and their ancient counterparts was perhaps best summarized by H. A. Lowenstam, “The present is the key to the Pleistocene… perhaps”.A growing data base from cores through modern reefs implies that much of the problem is related to real differences between what we think constitutes the interior of modern reefs and what is really there. Recognizable coral generally constitutes less than 30% of the reef fabric, based on examination of over 50 cores from a variety of reef types throughout the eastern Caribbean region. Volumetrically, loose sediment and void space comprise a significantly higher portion of the reef interior. Furthermore, obviously in-place and interlocking “framework” is conspicuously absent. Branching Acropora palmata is invariably found in a variety of orientations, implying largely detrital emplacement rather than the preservation of intact and undisturbed colonies. Head corals are generally separated by intervals of detritus or open cavities, rather than sitting atop older colonies. Where rigidity of the reef fabric can be observed, it is almost always a function of secondary encrustation by coralline algae and/or post-depositional marine cementation.The patterns seen in cores are supported by previous budget calculations of carbonate cycling in modern reefs around St. Croix. Bioerosion reduces original carbonate material to sediment, leaving recognizable coral to represent only a small part of the total reef volume. While still a significant component of the total reef fabric, few of the recognizable corals are bound together, and it is difficult to clearly demonstrate that the samples were recovered from life position (although some probably were). At Salt River, recovery was very low, and corals have been demonstrably moved from their original sites of growth.Effective modeling of ancient reefs must take into account the importance of secondary processes that reduce and redistribute the original carbonate material produced by corals. Combined with physical reworking, cementation and encrustation, these destructive processes result in a deposit that resembles more a pile of reef debris than the coherent assemblage of in-place, interlocking framework usually conjured up to represent the modern-reef interior. While still of great importance, constructional processes that are so evident on the reef surface must be viewed within the context of other physical, chemical and biological processes that are reflected in the growing body of core data from modern reefs in the western Atlantic and throughout the world.

We present thorough this review the developments in the field, point out their current limitations, and outline its timelines and unique potential. In order to do so we introduce the methods used in each of the advances in the application of deep learning (DL) to coral research that took place between the years: 2016–2018. DL has unique capability of streamlining the description, analysis, and monitoring of coral reefs, saving time, and obtaining higher reliability and accuracy compared with error-prone human performance. Coral reefs are the most diverse and complex of marine ecosystems, undergoing a severe decline worldwide resulting from the adverse synergistic influences of global climate change, ocean acidification, and seawater warming, exacerbated by anthropogenic eutrophication and pollution. DL is an extension of some of the concepts originating from machine learning that join several multilayered neural networks. Machine learning refers to algorithms that automatically detect patterns in data. In the case of corals these data are underwater photographic images. Based on “learned” patterns, such programs can recognize new images. The novelty of DL is in the use of state-of-art computerized image analyses technologies, and its fully automated methodology of dealing with large data sets of images. Automated Image recognition refers to technologies that identify and detect objects or attributes in a digital video or image automatically. Image recognition classifies data into selected categories out of many. We show that Neural Network methods are already reliable in distinguishing corals from other benthos and non-coral organisms. Automated recognition of live coral cover is a powerful indicator of reef response to slow and transient changes in the environment. Improving automated recognition of coral species, DL methods already recognize decline of coral diversity due to natural and anthropogenic stressors. Diversity indicators can document the effectiveness of reef bioremediation initiatives. We explored the current applications of deep learning for corals and benthic image classification by discussing the most recent studies conducted by researchers. We review the developments in the field, point out their current limitations, and outline their timelines and unique potential. We also discussed a few future research directions in the fields of deep learning. Future needs are the age detection of single species, in order to track trends in their population recruitment, decline, and recovery. Fine resolution, at the polyp level, is still to be developed, in order to allow separation of species with similar macroscopic features. That refinement of DL will allow such comparisons and their analyses. We conclude that the usefulness of future, more refined automatic identification will allow reef comparison, and tracking long term changes in species diversity. The hitherto unused addition of intraspecific coral color parameters, will add the inclusion of physiological coral responses to environmental conditions and change thereof. The core aim of this review was to underscore the strength and reliability of the DL approach for documenting coral reef features based on an evaluation of the currently available published uses of this method. We expect that this review will encourage researchers from computer vision and marine societies to collaborate on similar long-term joint ventures.

The reefs off Broward County exist as three shore-parallel, sequentially deeper terraces named the "inner", "middle", and "outer" reefs and also a shallower, nearshore ridge complex. These structures span the continental coast of southeast Florida from Palm Beach County to southern Miami-Dade County and were characterized as relict, early Holocene shelf-edge and mid-shelf reefs along with limestone ridges. Presently, the reefs are colonized by a fauna characteristic of West Atlantic/Caribbean reef systems. Scleractinian coral cover is low except for a few dense patches of Acropora cervicornis, while Acropora palmata is absent except for a few individual living colonies. Coral reef core-drilling is a useful analytical tool to extract observable and datable geological samples from within reefs. This technique was employed to retrieve 4 cores from the inner reef off Broward County to better understand its age, composition, and Holocene growth history. Sub-samples from corals in cores provided 7 new radiocarbon ages ranging from 7,860-5,560 cal BP, and reef accumulation rates of l.7-2.45 m/1,000 yrs were calculated from these ages. In addition, coral species composition and taphonomic characteristics were analyzed to identify former reef environments/reef zonation, and signals for inner reef termination. Reef zonation was detectable but no clear taphonomic signal for inner reef termination was evident. Current data and radiocarbon ages from all three Broward County reefs suggest that the outer reef accumulated from ~10.6-8 ka cal BP, the middle reef from at least ~5.8-3.7 ka cal BP, and the inner reef from ~7.8-5.5 ka cal BP. A lack of significant age overlaps between the three reefs has led to the assertion that they represent backstepping reefs in response to Holocene sea-level rise. This study has provided the oldest and youngest ages from the inner reef thus far, and confirms that reef backstepping from the outer reef to the inner reef occurred within just a few hundred years after the termination of the outer reef. The middle reef remains poorly understood and thus a definitive Holocene growth history and ultimately an understanding of their formation are still largely unknown.

A multi-disciplinary study of sediment core records from the Mingulay Reef Complex, a cold-water coral reefs system off western Scotland, highlights the potential of cold-water corals from which detailed centennial-scale palaeo-environmental reconstructions can be derived. This study provides a new insight on the mechanisms controlling Lophelia pertusa reef build-up, shifts in biodiversity, the physical/chemical/biological processes and the sedimentary regime. A detailed record of Mingulay Complex growth history shows unprecedented high average accumulation rates of 3 – 4 mm a-1. Marine radiocarbon reconstruction derived from paired 14C and U-series dated fossil corals revealed substantial abrupt oceanic shifts during the Holocene that have repetitively affected cold-water coral growth, eventually causing local disappearance. These periods of reduced accumulation rates are synchronous with other coral structures from the NE Atlantic illustrating basin wide events. Finally, trace/minor element ratios reproducibility within coral skeleton was investigated to test if palaeo-environmental reconstructions could be made from cold-water corals.

El análisis de estructuras paleokársticas ha atraído, en los últimos años, el interés de numerosos investigadores a la información que aportan a la geología aplicada y la paleogeomorfología. Estudios recientes se han centrado en la aplicación de técnicas de exploración del subsuelo debido a la escasez de afloramientos. En la presente Memoria se analizan íntegramente las formas de hundimiento pretéritas que afloran discontinuamente con gran detalle, en los acantilados de las costas meridional (plataforma de Llucmajor) y oriental (plataforma de Santanyí) de Mallorca, a lo largo de más de 75 km de línea de costa, afectando a las rocas carbonáticas del Mioceno superior. El estudio se ha centrado en la distribución geográfica, evolución geológica y las características geomorfológicas de estos paleocolapsos, con especial énfasis en su génesis, su relación con la arquitectura y distribución de las facies, así como en las formas y productos asociados.

Los paleocolapsos han sido descritos en su contexto litoestratigráfico y estructural dentro de las mencionadas plataformas carbonáticas, siendo este trabajo una contribución al conocimiento del karst en estas unidades geológicas y su relación con las fluctuaciones marinas. La karstogénesis queda reflejada en estas formas pretéritas donde se han observado depósitos y formas de disolución ligadas a la dinámica kárstica controlada, en el caso que nos ocupa, por las fluctuaciones del nivel del mar: brechas, sedimentos detríticos, cementos, así como distintos tipos y volúmenes de porosidad. La mayor parte de estas formas (sobre un total de 177), cuyas dimensiones en sección varían desde pocos metros hasta afloramientos con 28 m de altura y más de 100 m en la horizontal, se ubican en la plataforma de Santanyí a excepción de dos estructuras ubicadas en la plataforma de Llucmajor.

El análisis geológico y su relación con los paleocolapsos muestra como en la plataforma de Llucmajor éstos afectan a las facies de la Unidad Complejo Arrecifal (facies de back reef y frente arrecifal). Sin embargo, en la plataforma de Santanyí, los paleocolapsos afectan tanto a parte del Complejo Arrecifal (facies de back reef), como a la totalidad de la Unidad Calizas de Santanyí. A partir del estudio de la arquitectura de facies del Complejo Arrecifal en la plataforma de Llucmajor se ha establecido el modelo deposicional en la plataforma de Santanyí. Sin embargo, ésta última se encuentra compartimentada como consecuencia del control de dos fallas en dirección de orientación E-O en S'Algar y Na Magrana, donde se localiza el contacto entre facies de lagoon externo y talud arrecifal. No obstante, la cartografía y análisis de los lineamientos en dicha plataforma ha permitido identificar dos familias principales con dos direcciones dominantes; NE-SO y NO-SE, siendo la dirección E-O menos representativa. Se han observado fracturas distensivas y pequeñas fallas inversas miocenas asociadas al proceso de colapso, así como fracturas y fallas postmiocenas, y fracturas cuaternarias.

El estudio de la geometría en sección de los paleocolapsos pone de relieve que la formas en "V", "U" y conoidales son las más comunes. Han sido identificadas dos partes diferentes en un paleocolapso tipo: una inferior donde se observa la paleocavidad ubicada en la base del paleocolapso (lagoon externo y/o frente arrecifal), con una geometría irregular de dimensiones entre 1 m y 9 m rellena por sedimentos adyacentes y suprayacentes a ésta; y una parte superior, coincidente con los bordes de la estructura (lagoon interno/Calizas de Santanyí) buzando con inflexión conoidal hacia la paleocavidad.

Se han identificado cuatro tipos de brechas (crackle, crackle-laminae-split, de mosaico y caótica) en las estructuras de paleocolapso asociadas cada una de ellas a distintos niveles estratigráficos y, en algunos paleocolapsos, con una gradación vertical y lateral. Son característicos de estos depósitos los sedimentos detríticos (matriz) y los cementos asociados (vadosos y freáticos). En general, el cemento domina sobre la matriz en la zona inferior del paleocolapso, mientras que por encima, es la matriz la que domina sobre el cemento. El análisis por difracción de Rayos X de la matriz indica para la muestra total que la calcita es el mineral principal y el cuarzo el mineral secundario. En la fracción arcilla, la moscovita, la illita y la caolinita son los minerales más comunes. De ello, junto con el estudio de láminas delgadas en estos depósitos, donde se han observado tamaños de grano en el cuarzo superior a 2 mm, se deduce un ambiente de sedimentación subsuperfical y otro subaéreo de lo que se extrae un origen, proceso de transporte y sedimentación diversos, así como la evolución cristaloquímica en determinados minerales. Los cementos son de naturaleza calcítica, con contenidos relativamente altos en magnesio para los freáticos y bajos para los vadosos. Para el estudio de la porosidad en los paleocolapsos se ha procedido a su clasificación en dos tipos principales, interclasto e intraclasto, a partir de las cuales se ha estudiado la macro y microporosidad. La brecha caótica de colapso es la que presenta volúmenes de porosidad más elevados y tipologías diversas.

El análisis de isótopos estables muestra una gran homogeneidad entre la composición isotópica de los cementos, con valores en δ18O y δ13C ligeros, lo que indica condiciones análogas de precipitación, con dominio de aguas dulces sobre las saladas. Tanto la marca del oxígeno como del carbono parecen indicar que los cementos se depositaron en un período interglaciar coincidente con algún estadio isotópico impar.

El estudio de la arquitectura de facies de la plataforma de Llucmajor ha permitido elaborar un modelo genético de ocurrencia para los paleocolapsos y su ubicación espacio-temporal. Dicho modelo, ha sido corroborado por la relación entre la distribución de facies y paleocolapsos en la plataforma de Santanyí, por la observación en algunos paleocolapsos de sedimentos a techo de la Unidad Calizas de Santanyí que sellan la estructura, así como por el tipo de brechas características de colapsos sinsedimentarios (brecha crackle-laminae-split), que muestran una deformación dúctil de los materiales cuando éstos no estaban completamente consolidados, dando lugar a formas laxas de bajo ángulo. Los procesos genéticos que dieron lugar a los paleocolapsos kársticos están directamente relacionados con la alta frecuencia de fluctuación del nivel del mar durante el Mioceno superior, la misma que controló la arquitectura de facies y la posición del nivel freático. Las oscilaciones del nivel freático causaron la alternancia de dominios freáticos y vadosos así como, de agua dulce y agua salada en la interfase, provocando la disolución de los parches coralinos y el posterior hundimiento del techo de las cavidades.

El estudio integral de todos estos aspectos junto con el análisis de una red de paleocauces y una playa fósil, ha permitido realizar una reconstrucción paleogeográfica desde el Messiniense en la plataforma de Santanyí e identificar estructuras de paleocolapso postmiocenas y cuaternarias. Con estos datos se ha procedido a la comparación de los paleocolapsos kársticos con otras estructuras similares en el País Vasco y Las Islas de Malta, de lo que se extraen analogías y diferencias, determinadas fundamentalmente por el orden de fluctuación del nivel del mar.

Por último, se discute el papel de los paleocolapsos kársticos como elementos que contribuyen en cierta medida a la ocurrencia de hidrocarburos en plataformas carbonáticas, pudiendo ser excelentes reservorios debido al gran número de afloramientos, el volumen de roca afectada y a su elevada porosidad y permeabilidad.
Paleokarst tend to differ from studies of recent and modern karst landforms though is important the genetic understanding of the karst processes for analysis a paleokarst structure. Paleokarst systems form an important class of carbonate record and they have a pronounced lateral and vertical spatial complexity that results from a complex history of formation. Most of the known karst systems are epigenetic and they are the result of near-surface karst processes during periods of subaerial exposure and latter burial compaction and diagénesis. Scale, porosity types and spatial complexities of these paleokarst systems depends on the carbonate rock solubility, paleoclimatic conditions, lowering of base level either by tectonic uplift or sea-level fall and time of subaerial exposure. Uplift, in addition, commonly induces fracturing and faulting that further control karst development. Ascertaining and predicting paleokarstic heterogeneities within carbonate rocks are strategic to fluids field development and optimum production. With current subsurface methods, however, most of the smaller-scale stratigraphic architecture and diagenetic facies are difficult to define. Predictive models for exploration and development are best made from outcrop studies of well-exposed examples. Accuracy for prediction of these models depends on the detailed understanding of the genetic factors controlling their geometries, scale, pore networks and spatial complexities of these potential karstic store. Miocene carbonates (Upper Tortonian-Lower Messinian) in Mallorca Island are composed of reefal (Reef Complex) and shallow water carbonates (Santanyí Limestone) that prograded across platforms surrounding paleoislands. The contact between the Reef Complex and the Santanyí Limestone is a subaerial erosion surface with paleokarst features. The shallow-water carbonates beds both the lagoonal beds of the Reef Complex and basal beds of the Santanyí Limestone, are affected by paleocollapse structures produced by roof collapse of caverns developed in the underlying Reefal Complex. These paleocollapse structures affecting to the carbonate platform allows to propose a genetic model to explain the origin of these paleosink, that are related to early diagenetic processes induced by high-frequency sea-level fluctuations, the same sea-level fluctuations that controlled the facies architecture of the carbonate platforms.

Cartography and study of lineaments and fractures on Santanyí Platform have permitted identified two principals groups with two main directions: NE-SO and NO-SE. Have been observed distensiva fractures and Miocene small inverse faults related with de breackdwon phenomena. Moreover, postmiocenes and quaternary faults and fractures have been recognized.

The geometry of paleocollapse structures is commonly (in section) as "V", "U" or funnel. The size is variable from few meters of long to thousands meters, and few meters of weigh to thirteen meters. Breccias has been classified as crackle, crackle-laminae-split, mosaic and chaotic types. Chaotic breccias grade from matrix-free, clasts-supported breccias to matrix-supported breccias. The matrix mineralogy is compose in the total sample for calcite in the major part and quartz in less quantity. However, same structures present quartz as principal mineral. To the clay fraction, caolinite, illite and moscovite are the most general mineral present.

The geochimical sediment (carbonate) are filling a part of interclaste breccias porosity. This is commonly phreatic speleothems. Isotopic studies of this sediments show δ18O and δ13C contents negatives. This fact could indicate a fresh water environment deposition

‘Ancient reefs and islands’ illustrates that the present day ecology and organization of species on a reef and their behaviour—basically how a reef works—is the result of a very long heritage. Limestone-deposited structures of the Pre-Cambrian, Cambrian, Ordovician, Carboniferous, Permian, Triassic, and Cretaceous periods, the organisms that created them (including ancestors of today’s sponges and corals), and key extinctions are described along with the three different kinds of coral islands seen around the tropical world: coral cays, islands with a solid limestone core, and volcanic or basaltic islands fringed with coral reef. The future of current reef systems, the effects of ocean changes, and the resulting impact on humanity are considered.

Healthy reefs provide a habitat for an immense number of fish that come in a variety of shapes, sizes, and colours. No other natural habitat in the ocean shows this diversity and abundance. About a quarter of all marine species may be found on coral reefs even though this habitat occupies only one or two per cent of the area of the earth. ‘Reef fish and other major predators’ describes the diverse feeding ecology of reef fishes; coral reef predators such as the colourful crown of thorns starfish, Acanthaster plancii; symbiotic relationships between different species of fish or with different invertebrates; and the dangers of overfishing in reef communities.

Coral Whisperers captures a key moment in the history of coral reef science and of environmental conservation at large. Drawing on more than one hundred interviews,the book documents the physical, intellectual, and emotional plight of coral scientists and their painstaking deliberations as they struggle to understand and save corals from what many of these scientistshave come to see as the corals’inevitable catastrophic future on a rapidly warming and otherwise assaulted planet.We are here in the thick of contemporary coral science, and we can feel its urgency: the experts, who are witnessing massive coral death around the planet, both grieve for this death and must simultaneously narrate it. Yet despite the desperate realities confronting corals in the Anthropocene, coral scientists have not given up hope. Through their engaging narratives, corals emerge as a sign, a measure, and a way out of the imminent catastrophe facinglife on earth.

The intricate coastline of Southeast Asia, and its many islands and island groups—Indonesia alone has over 17 500 islands—contains 32 per cent (91 700 km2) of the world’s shallow coral reefs (Spalding, Ravilious, and Green 2001). While sedimentary regimes appear to restrict reef development in the East China Sea, the Gulf of Thailand, the South China Sea, and around the island of Borneo, reefs are well developed elsewhere. Fringing reefs characterize island coastlines, and there are also barrier reefs and, in the deeper waters of the South China Sea and to the east, atoll-like reef structures. Although the region has a distinguished history of reef studies—in which the pioneering work of R. B. Seymour Sewell, J. H. F. Umbgrove, and Ph. H. Kuenen on the Snellius expedition (1929–30) come particularly to mind—the lack of detailed information about many areas remains considerable. The coral reefs, and their associated shallow-water ecosystems, within this region are the product of both historical and contemporary processes. A wide range of hypotheses to explain coral distributions have been proposed. These include the importance of the widespread availability of suitable shallow substrates for coral growth with submergence histories determined by regional tectonic and sea-level dynamics (e.g. Hall and Holloway 1998), the variety of habitats present (e.g. Wallace and Wolstenholme 1998), and the more contemporary roles of high sea-surface temperatures and ocean current circulation patterns, including the dynamics of western Pacific Ocean–eastern Indian Ocean connectivity (Tomascik et al. 1997a). Both sets of controls show wide variation across the region. Thus, for example, geological settings range from tectonically stable platforms to rapidly uplifting plate collision zones of considerable seismic and volcanic activity. Present-day environments vary from equable, tranquil interior seas to cycloneand swell wave-dominated environments on the region’s margins. Added to these controls are the perturbations introduced by, for example, periodic coral bleaching and biological catastrophes (e.g. Crown of Thorns starfish infestations; Lane 1996). Taken as a whole, therefore, the coral reefs of Southeast Asia demonstrate enormous complexity and considerable dynamism. These reef resources are, however, under considerable pressure from large, and growing, populations and economic development.

Almost all the studies performed during the past century have shown that drought is not the result of a single cause. Instead, it is the result of many factors varying in nature and scales. For this reason, researchers have been focusing their studies on the components of the climate system to explain a link between patterns (regional and global) of climatic variability and drought. Some drought patterns tend to recur frequently, particularly in the tropics. One such pattern is the El Niño and Southern Oscillation (ENSO). This chapter explains the main characteristics of the ENSO and its data forms, and how this phenomenon is related to the occurrence of drought in the world regions. Originally, the name El Niño was coined in the late 1800s by fishermen along the coast of Peru to refer to a seasonal invasion of south-flowing warm currents of the ocean that displaced the north-flowing cold currents in which they normally fished. The invasion of warm water disrupts both the marine food chain and the economies of coastal communities that are based on fishing and related industries. Because the phenomenon peaks around the Christmas season, the fishermen who first observed it named it “El Niño” (“the Christ Child”). In recent decades, scientists have recognized that El Niño is linked with other shifts in global weather patterns (Bjerknes, 1969; Wyrtki, 1975; Alexander, 1992; Trenberth, 1995; Nicholson and Kim, 1997). The recurring period of El Niño varies from two to seven years. The intensity and duration of the event vary too and are hard to predict. Typically, the duration of El Niño ranges from 14 to 22 months, but it can also be much longer or shorter. El Niño often begins early in the year and peaks in the following boreal winter. Although most El Niño events have many features in common, no two events are exactly the same. The presence of El Niño events during historical periods can be detected using climatic data interpreted from the tree ring analysis, sediment or ice cores, coral reef samples, and even historical accounts from early settlers.

Several physical features combine to make Southeast Asia one of the most distinct and unique coastal regions in the world. The mainland or continental part of Southeast Asia consists of a number of peninsulas extending south and southeast from the Asian continent and separated by gulfs and bays. The world’s two largest archipelagos form the islands of Southeast Asia. During much of the Pleistocene, a large part of the South China Sea was dry land, and the islands of Sumatra, Java, and Borneo were linked to the mainland by the exposed shallow Sunda Shelf. Southeast Asia comes under the influence of the monsoons, or seasonal winds, which have an important impact on its coasts. The region is also a high biodiversity zone, characterized by its rich coral reefs and mangroves. This chapter examines the coastal environments of Southeast Asia in three stages. First, the major elements that make the coastal environments of Southeast Asia distinctive are discussed. The focus is on the coastal processes, as the geological framework and Quaternary have been covered in earlier chapters. Secondly, the various coastal environments in the region (excluding estuaries and deltas discussed in Chapter 13) are described next in terms of their extent, characteristics, and significance, with sufficient examples given to show their variability. Finally, the chapter ends with an assessment of the major environmental problems facing the region’s coastal environments—coastal erosion and rising sea level associated with climate change. Overall, this chapter provides the physical basis for a better appreciation of coastal development in Southeast Asia. The coastal environments of Southeast Asia bear the impact of significant geological and climatic factors. Geologically, the core of the region is an extension of the Eurasian Plate meeting the Indo-Australian and the Pacific Plates and two lesser ones (Philippines and Molucca Sea) with mountain chains trending in a general north–south direction. The island of New Guinea is part of the Indo-Australia Plate. Island arcs have developed along the convergent margins, and many are volcanically active and also associated with shallow to deep earthquakes.

Four hundred million years ago, Taum Sauk Mountain was a high ridge on a solitary island in a vast Paleozoic sea surrounded by coral reefs. Geologists describe it as a landscape of lofty volcanoes. It was one of the few parts of present-day North America that were never submerged under a primordial sea. At 1,772 feet above sea level, Taum Sauk Mountain has been worn down through the ages but is still the highest point in Missouri. It lies on the crest of a mountain chain several times older than the Appalachians. The Taum Sauk section of the Ozark Trail is one of the most beautiful stretches in the Ozarks. The twelve-and-a-half-mile tract that runs from the blue pools and massive boulders of Johnson’s Shut-Ins State Park to the top of Taum Sauk Mountain is studded with waterfalls, thick woodlands, rocky glades, and beaver ponds. It is a good place for reflecting on primeval things, gaining a long-range perspective on one’s life, discerning what has gone and what may yet need to come. This is one of the boons of wilderness hiking. Turning onto route CC off Highway 21 in Iron County on a Friday afternoon, I’ve made it to the top of the mountain a few hours before dark. My plan is to hike down the trail below Mina Sauk Falls, spending the night in the woods near Devil’s Tollgate and moving on toward Johnson’s Shut-ins the next day. I’ve come to an intriguing place. In wet weather, the water cascades 132 feet down rock ledges, forming the highest waterfall in the state. Below the falls the trail passes through an eight-foot-wide opening in a thirty-foot-deep section of magma that was part of an ancient volcanic caldera. Hardened now into fine-grained rhyolite, the geological oddity is dubbed the Devil’s Tollgate. A pioneer wagon road once passed between its stone walls, making a convenient site for bandits to hide. The locals claim that Jesse James hid out on the mountain after robbing the Ironton Train in 1874. Until the State Park System built a road to its top in the 1950s, Taum Sauk Mountain was a remote and isolated place.

A little girl in Raytown, Missouri, used to spend part of almost every day in a special place in the woods near her house. The place had a calming effect on her. “Sometimes I go there when I’m mad . . . and then, just with the peacefulness, I’m better. I can come back home happy, and my mom doesn’t even know why.” In his book Last Child in the Woods, Richard Louv recounts the end of this fifth grader’s story. “And then they just cut the woods down. It was like they cut down part of me.” I know this same feeling. When I was her age, I watched the prairiesavannah I loved to explore turned into a housing development, chasing away my friends, the meadowlarks. I watched my aging Irish poet friend, Ken Olsen, try to fight the city to save the little bit of woods next to his house from being turned into an apartment complex. The loss nearly gave him a heart attack … or it did give him one, just not one that could be seen. Another friend mourned for weeks after the city cut down the oak in front of her apartment complex that offered dappled green shade to her fourth-floor home. It’s grief, pure and simple. But with all grief, life goes on, sometimes even when we don’t want it to. And there’s hope in that. The land systems long to rejuvenate, just as we long to have them back. Leopold’s restoration work at the Shack and the Arboretum have expanded exponentially, into every ecosystem on land and even into ocean ecosystems, such as coral reefs, kelp beds, tidal communities, and oyster beds. Because so much damage has been done, this is one of the most vibrant, growing, and needed areas of the Leopold legacy. Steven Brower, a landscape architect and Leopold family historian from Burlington, often walks the woods, caves, and bottomlands where Aldo roamed as a child. Brower’s eyes penetrate the landscapes with a kind of x-ray vision, seeing what once was underneath what is today.