The impact of the Mid-Pleistocene Transition on the composition of submerged reefs of the Maui Nui Complex,Hawaii

The submarine reef terraces (L1–L12) of the Maui Nui Complex (MNC—the islands of Lanai, Molokai, Maui and Kahoolawe) in Hawaii provide a unique opportunity to investigate the impact of climate and sea level change on coral reef growth by examining changes in reef development through the Mid-Pleistocene Transition (900–800 ka). We present an analysis of the biological and sedimentary composition of the reefs that builds directly on recently published chronological and morphological data. We define nine distinct limestone facies and place them in a spatial and stratigraphic context within 12 reef terraces using ROV and submersible observations. These include oolitic, two coral reef, two coralline algal nodule, algal crust, hemi-pelagic mud, bioclastic and peloidal mud facies. These facies characterise environments from high energy shallow water coral reef crests to low energy non-reefal deep-water settings. Combining the bottom observations and sedimentary facies data, we report a shift in the observed sedimentary facies across the submerged reefs of the MNC from dominant shallow coral reef facies on the deep reefs to coralline algae dominated exposed outcrop morphology on the shallower reefs. We argue that this shift is a reflection of the change in period and amplitude of glacioeustatic sea level cycles (41 kyr and 60–70 m to 100 kyr and 120 m) during the Mid-Pleistocene Transition (MPT, ~ 800 ka), coupled with a slowing in the subsidence rate of the complex. The growth of stratigraphically thick coral reef units on the deep Pre-MPT reefs was due to the rapid subsidence of the substrate and the shorter, smaller amplitude sea level cycles allowing re-occupation and coral growth on successive cycle low-stands. Longer, larger amplitude sea level cycles after the MPT combined with greater vertical stability at this time produced conditions conducive to deep-water coralline algae growth which veneered the shallower terraces. Additionally, we compare reef development both within the MNC, and between the MNC and Hawaii. Finally we suggest that climatic forcings such as sea-surface temperature and oceanographic currents may also have influenced the distribution of coral species within the sample suite, e.g., the disappearance of the Acropora genus from the Maui Nui Complex in the Middle Pleistocene.     

Paleogene terrigenous (flysch) sequences in Etoloakarnania region (W. Greece). Plankton stratigraphy and paleoenvironmental implications

Based on calcareous nannofossils and planktonic foraminifera1 biostratigraphic data from flysch sequences, we give evidence for the paleoenvironmental evolution of Gavrovo and Ionian foreland basins (External Hellenides, Etoloakarnania region). Our data suggest that the onset of clastic sedimentation in both foreland basins in the study area is chronostratigraphically placed at Late Eocene (from 36.2-34.4 Ma; nannofossil biozones NP19-20, planktonic foraminifera biozones P16-17). During the earliest Oligocene (NP21-22 nannofossil biozones/34.4-32.45 Ma), both basins represent restricted accumulation of sediments, mainly composed of clays and silts. The presence of thick flysch deposits, accumulated during Early Oligocene (33.4-30 Ma, nannofossil zone NP23), indicates an increasing rate of sediment supply. The flysch sequences in the Ionian basin are associated with a distal depositional environment, while in the same time the sedimentation in the external part of Gavrovo basin is related to a more proximal environment that is gradually deepening. On the contrary, the internal part of Gavrovo basin is characterised by deep-water facies, deposited in the Early Oligocene. At the end of Early Oligocene and the onset of Late Oligocene (nannofossil zone NP24/30-27.2 Ma, planktonic foraminifera zone P21), the deposition of coarse grained sediments in both basins indicates a shift to shallower depositional environment. The accumulation of fine-grained sediments during Late Oligocene (27.2-23.2 Ma, NP25 nannofossil biozone) in the Ionian basin marks the youngest flysch sediments in the Etoloakarnania region and specifies the time of the Gavrovo nappe emplacement on the Ionian zone. Moreover the emplacement of Pindos nappe on the Gavrovo zone is estimated between 30-27.2 Ma (NP24 biozone) as supported by the nannofossil analysis of samples in front of Pindos thrust.     

Palynological evidence for Late Miocene-Pliocene vegetation evolution recorded in the red clay sequence of the central Chinese Loess Plateau and implication for palaeoenvironmental change

In northern China, the Late Miocene-Pliocene red clay in the eastern Loess Plateau fills a gap of climate records between the well-known loess-soil sequences of the last 2.6 Ma and the Miocene loess-soil sequences from the western Loess Plateau. Previous studies indicate that the red clay is also of wind-blown origin, covering the period from ∼ 7-8 to ∼ 2.6 Ma. The red clay therefore provides a good archive to reconstruct paleoecological succession and paleoclimate change. In this study, a palynological investigation was conducted on the late Miocene-Pliocene red clay sequence at Xifeng, central Loess Plateau, which provides new insights into the nature of the evolution of vegetation and climate change from ∼ 6.2 to ∼ 2.4 Ma. Our results show that during this period the central Loess Plateau region was covered mainly by a steppe vegetation, indicating long lasting dry climatic condition. Three vegetational zones were recognized during this period. Zone A (∼ 6.2 to ∼ 5.8 Ma) is characterized by a steppe ecosystem; Zone B (∼ 5.8 to ∼ 4.2 Ma) is characterized by a significant increase of temperate forest plants, indicating a relatively humid regional climate; Zone C (∼ 4.2 to ∼ 2.4 Ma) indicates a typical steppe ecosystem. The vegetation shift at about 4.5-3.7 Ma, when the temperate forest plants decrease, the vegetation gradually changed to typical grassland and even to desert steppe. This is interpreted to represent a drying event. The uplift of the Tibetan Plateau at about 4.5 Ma that resulted in the intensification of the monsoon reversal is thought to have played an important role in this significant ecological change. High-latitude cooling may have partially contributed to the climate shift during ∼ 4.5 to ∼ 3.7 Ma in the Loess Plateau region, and most likely was the driving force for the ecological shift at about 3.7 Ma.     

Coral community structure and risk assessment of high-latitude reefs at Sodwana Bay,South Africa

The importance of studying coral communities at different spatial scales is acknowledged in a growing volume of scientific literature, and principles of landscape ecology were thus used to elucidate the patterns in coral community structure on the high-latitude reefs in South Africa. These reefs are at the southernmost distribution of this fauna in Africa, are surprisingly species rich, and represent a biodiversity peak in this fauna south of the equator, regardless of the marginal nature of the environment. Coral community patterns were identified on and between the reefs at Sodwana Bay, justifying the grouping of reef areas in distinct zones. A number of landscape components were identified, ranging from the entire reef complex (10 km scale), individual reefs (1 km scales) and reef zones, to components that were separated using multivariate statistical analysis of transect data. These components transcended spatial similarities, e.g. the fore-reef on Five-mile Reef was not similar to the fore-reef on Seven-mile Reef, but was rather grouped with the reef flat on Two-mile Reef. This information was “translated” into an index of management intervention, based on risk assessment, and was generated using parameters that measure susceptibility to crown-of-thorns feeding, bleaching, diver-related damage and swell-induced breakage. We also assessed was the time elapsed since the last major disturbance and the proximity to the only boat launch site, a proxy measure of continuous disturbance. The risk assessment suggested that conservation management is most needed in the stable and “climax” coral communities that are usually characterised by a near-equal mix of hard and soft corals at maximal coral species diversity.     

Near-shore bathymetry and reef biotopes of Henderson Island, Pitcairn Group

The coral reef which surrounds two thirds of Henderson Island, Pitcairn Group, consists of a reef flat, reef margin and fore-reef which slopes gradually into deeper water. The range of sublittoral habitats provided by this topography is limited, reflecting a low level of coral diversity. Spur and groove formations of the fore-reef are present around the northern end of the island which contrasts with the south-western corner, where, in the absence of a fringing reef platform, subaerial cliff faces are fronted by a cliff foot submarine 'trench'. In general, live coral cover on the fore-reef was estimated at between 10–30%, though at sites off the east coast it reached 80%. The associated communities, particularly of sessile filter-feeding groups, were found to be impoverished. The two factors of biogeographical isolation and of local bioerosion processes are proposed as being the main reasons for the depauperate nature of the island's reef. Brief notes are included on the lagoon and fore-reef bathymetry and habitats of Ducie and Oeno Atolls for comparative purposes.     

The paleoclimate of the Eastern Mediterranean during the transition from early to mid Pleistocene (900 to 700 ka) based on marine and non-marine records: An integrated overview

Climate change is frequently considered an important driver of hominin evolution and dispersal patterns. The role of climate change in the last phase (900-700 ka) of the Middle Pleistocene Transition (MPT) in the Levant and northeast Africa was examined, using marine and non-marine records. During the MPT the global climate system shifted from a linear 41 k.yr. into a highly non-linear 100 k.yr. system, considerably changing its global modulation. Northeast Africa aridity further intensified around 950 ka, as indicated by a sharp increase in dust flux, and a jump to overall higher levels thereafter, coinciding with a lack of sapropels in the deep eastern Mediterranean (930-690 ka). The increased dust flux centering at ∼800 ka corresponds to the minima in 400 k.yr. eccentricity, a minima in 65 °N solar forcing and in the weakest African monsoon precession periodicity. This resulted in expansion of hyper-arid conditions across North Africa, the lowest lake levels in eastern Africa and the lowest rainfall in the Nile River headwaters. In the eastern Mediterranean an increasing continental signature is seen in glacial stages 22 (∼880 ka) and 20 (∼800 ka). Lower arboreal pollen values also indicate arid conditions during these glacial stages. The southern and eastern parts of the Negev Desert, unlike its northern part, were hyper-arid during the MPT, making them highly unsustainable. The fluctuations in the stands of Lake Amora follow global climate variability but were more moderate than those of its last glacial Lake Lisan successor. In the northern Jordan-Valley Hula Lake, frequent fluctuations in lake level coincide with both global climate changes and minor changes in water salinity varying from fresh to oligohaline. It appears therefore that the most pronounced and widespread deterioration in climate occurred in northeast Africa from 900 to 700 ka, whereas in the Levant the corresponding climatic changes were more moderate.     

Paleoceanography of coral reefs in the Hawaiian-Emperor Chain – revisited

Coral Reefs -  This paper is a review of the present knowledge of coral reef ecology and paleoecology in the Hawaiian-Emperor Chain during the last 70 Ma. Research on fossil coral deposits...     

Tectonic subsidence provides insight into possible coral reef futures under rapid sea-level rise

Sea-level rise will change environmental conditions on coral reef flats, which comprise extensive habitats in shallow tropical seas and support a wealth of ecosystem services. Rapid relative sea-level rise of 0.6 m over a relatively pristine coral reef in Solomon Islands, caused by a subduction earthquake in April 2007, generated a unique opportunity to examine in situ coral reef response to relative sea-level rise of the magnitude (but not the rate) anticipated by 2100. Extent of live coral was measured from satellite imagery in 2003, 2006, 2009 and 2012. Ecological data were obtained from microatolls and ecological surveys in May 2013. The reef was sampled at 12 locations where dense live hard coral remained absent, remained present or changed from absent to present following subsidence. Ecological data (substratum depth, live coral canopy depth, coral canopy height, substratum suitability, recruitment, diversity and Acropora presence) were measured at each location to identify factors associated with coral response to relative sea-level rise. Vertical and horizontal proliferation of coral occurred following subsidence. Lateral expansion of live coral, accomplished primarily by branching Acropora spp., resulted in lower diversity in regions which changed composition from pavement to dense live coral following subsidence. Of the ecological factors measured, biotic factors were more influential than abiotic factors; species identity was the most important factor in determining which regions of the reef responded to rapid sea-level rise. On relatively pristine reef flats under present climatic conditions, rapid relative sea-level rise generated an opportunity for hard coral to proliferate. However, the species assemblage of the existing reef was important in determining response to sea-level change, by providing previously bare substrate with a source of new coral colonies. Degraded reefs with altered species composition and slower coral growth rates may be less able to respond to climate change-induced sea-level changes.     

Uplift of the Ou Backbone Range in Northeast Japan at around 10 Ma and its implication for the tectonic evolution of the eastern margin of Asia

The Late Cenozoic uplift history of a sedimentary basin located in the axial part of the Ou Backbone Range, Northeast Japan, was studied using detailed mapping, fission-track dating and basin analysis. The subsidence analysis of the basin clarified the more complex stepwise uplift of the Ou Backbone Range. Three stages of uplift have been recognized and are interpreted to be the result of compressional stress, possibly accompanied by basin inversion. The three stages are identified as (1) a phase of surface uplift and regional unconformity (12-9 Ma), (2) a stage of differential uplift and compression (6.5-3 Ma) and (3) an intense compression stage (∼ 3 Ma). In the first stage, the eastern sector of the Backbone Range uplifted and a notable unconformity was formed at ∼ 10 Ma. The western sector remained submerged, suggesting that the eastern sector uplifted earlier than the western sector. Although the first uplift stage has been regarded as a tectonically quiet period in Northeast Japan, this tectonic event at ∼ 10 Ma is supposed to have a regional origin because coeval tectonic events took place across all Northeast Japan, as well as on the eastern margin of Asia. This study thus provides new insights into the Neogene tectonic evolution in the eastern margin of Asia.     

Middle Eocene–late Oligocene climate variability: Calcareous nannofossil response at Kerguelen Plateau,Site 748

A major deterioration in global climate occurred through the Eocene–Oligocene time interval, characterized by long-term cooling in both terrestrial and marine environments. During this long-term cooling trend, however, recent studies have documented several short-lived warming and cooling phases. In order to further investigate high-latitude climate during these events, we developed a high-resolution calcareous nannofossil record from ODP Site 748 Hole B for the interval spanning the late middle Eocene to the late Oligocene (~ 42 to 26 Ma). The primary goals of this study were to construct a detailed biostratigraphic record and to use nannofossil assemblage variations to interpret short-term changes in surface-water temperature and nutrient conditions. The principal nannofossil assemblage variations are identified using a temperate-warm-water taxa index (Twwt), from which three warming and five cooling events are identified within the middle Eocene to the earliest Oligocene interval. Among these climatic trends, the cooling event at ~ 39 Ma (Cooling Event B) is recorded here for the first time. Variations in fine-fraction δ¹⁸O values at Site 748 are associated with changes in the Twwt index, supporting the idea that significant short-term variability in surface-water conditions occurred in the Kerguelen Plateau area during the middle and late Eocene. Furthermore, ODP Site 748 calcareous nannofossil paleoecology confirms the utility of these microfossils for biostratigraphic, paleoclimatic, and paleoceanographic reconstructions at Southern Ocean sites during the Paleogene.     

Macroborers within coral framework at Discovery Bay, north Jamaica: species distribution and abundance, and effects on coral preservation

 Macroboring organisms are recognised as key agents of reef framework modification and destruction, and while recent studies in the Pacific have improved understanding of spatial variations in macroboring community structure, and rates of macroboring within individual reefs, comparable studies from the Caribbean are largely lacking. This study assesses the distribution of macroboring species and the degree of framework infestation across the reefs at Discovery Bay, north Jamaica. Although individual species of borers exhibit variable distributions across the reef, relative abundances of the main groups of macroborers (sponges, bivalves, worms) illustrate clear distributional trends. Sponges are dominant at fore-reef sites, while sipunculan and polychaete worms are only of importance at back-reef/lagoon and shallow fore-reef sites. Bivalves are locally important within back-reef and lagoon patch reef framework. Average percentages of internal bioerosion (macroboring) vary between sites, but are highest at back-reef and deep fore-reef sites. No systematic pattern of variation occurs within back-reef/lagoon samples, but a significant trend of increased macroboring is recognised with increased water depth on the fore-reef. In addition, significant differences in terms of the susceptibility of individual coral species are recognised. These factors are likely to result in biasing of the fossil record, with variable styles of preservation evident both between sites (i.e. with depth/environment) and within sites (i.e. between coral species). Accepted: 1 June 1998     

Occurrence of thick Ethmodiscus oozes associated with a terminal Mid-Pleistocene Transition event in the oligotrophic subtropical South Atlantic

Within generally calcareous sediment sequences, layers of variable thickness of the giant diatom Ethmodiscus were found in five cores recovered in the Subtropical South Atlantic between 23° and 33°S from both sides of the Mid-Atlantic Ridge. Two types of oozes occur: (almost) monospecific layers of Ethmodiscus and layers dominated by Ethmodiscus, with several accompanying tropical/subtropical, oligotrophic-water diatoms. The two thickest Ethmodiscus layers occur in GeoB3801-6 around 29°S, and accumulated during late MIS 14 and MIS 12, respectively. Downcore concentrations of Ethmodiscus valves range between 3.4 ? 10⁴ and 2.3 ? 10⁷ valves g^− 1. We discuss the ooze formation in the context of migration of frontal systems and changes in the thermohaline circulation. The occurrence of Ethmodiscus oozes in sediments underlying the present-day pelagic, low-nutrient waters is associated with a terminal event of the Mid-Pleistocene Transition at around 530 ka, when the ocean circulation rearranged after a period of reduced NADW production.     

Geological summary of the Busidima Formation (Plio-Pleistocene) at the Hadar paleoanthropological site, Afar Depression, Ethiopia

The Hadar paleoanthropological site in Ethiopia preserves a record of hominin evolution spanning from approximately 3.45 Ma to 0.8 Ma. An angular unconformity just above the ca. 2.95 Ma BKT-2 complex divides the sediments into the Hadar Formation (ca. 3.8-2.9 Ma) and the Busidima Formation (ca. 2.7-0.15 Ma). The unconformity is likely a response to a major tectonic reorganization in the Afar Depression, and activation of the As Duma fault near the Ethiopian Escarpment (west of Hadar) created a half-graben in which the Busidima Formation was deposited. The pattern and character of sedimentation in the region changed dramatically above the unconformity, as cut-and-fill channel conglomerates and silt-dominated paleosols that comprise the Busidima Formation stand in sharp contrast to the underlying deposits of the Hadar Formation. Conglomerate deposition has been related to both the perennial, axial paleo-Awash and ephemeral, escarpment-draining tributaries. Overbank silts have yielded fossils attributed to early Homo and Oldowan stone tools. Numerous tuffaceous deposits exist within the Busidima Formation, but they are often spatially limited, fine-grained, and reworked. Recent work on the tephrostratigraphic framework of the Busidima Formation at Hadar has identified at least 12 distinct vitric tephras and established the first geochemical-based correlations between Hadar and the neighboring project areas of Gona and Dikika. Compared to Gona and Dikika, where Busidima Formation sediments are exposed over large areas, the highly discontinuous sediments at Hadar comprise less than 40 m in composite section and are exposed over an area of <20 km², providing only snapshots into the 2.7-0.15 Ma window. The stratigraphic record at Hadar confirms the complex depositional history of the Busidima Formation, and also provides important details on regional stratigraphic correlations and the pattern of deposition and erosion in the lower Awash Valley reflective of its tectonic history.     

Neogene reef coral assemblages of the Bocas del Toro region, Panama: the rise of Acropora palmata

Temporal patterns are evaluated in Neogene reef coral assemblages from the Bocas del Toro Basin of Panama in order to understand how reef ecosystems respond to long-term environmental change. Analyses are based on a total of 1,702 zooxanthellate coral specimens collected from six coral-bearing units ranging in age from the earliest Late Miocene to the Early Pleistocene: (1) Valiente Formation (12–11 Ma), (2) Fish Hole Member of the Old Bank Formation (5.8–5.6 Ma), (3) La Gruta Member of the Isla Colon Formation (2.2–1.4 Ma), (4) Ground Creek Member of the Isla Colon Formation (2.2–1.4 Ma), (5) Mimitimbi Member of the Urracá Formation (1.2–0.8 Ma), and (6) Hill Point Member of the Urracá Formation (1.2–0.8 Ma). Over 100 coral species occur in the six units, with faunal assemblages ranging from less than 10% extant taxa (Valiente Formation) to over 85% extant taxa (Ground Creek Member). The collections provide new temporal constraints on the emergence of modern Caribbean reefs, with the La Gruta Member containing the earliest occurrence of large monospecific stands of the dominant Caribbean reef coral Acropora palmata, and the Urracá Formation containing the last fossil occurrences of 15 regionally extinct taxa. Canonical correspondence analysis of 41 Late Miocene to Recent reef coral assemblages from the Caribbean region suggests changes in community structure coincident with effective oceanic closure of the Central American Seaway (~3.5 Ma). These changes, including increased Acropora dominance, may have contributed to a protracted period of elevated extinction debt prior to the major peak in regional coral extinctions (~2–1 Ma).     

Palaeomagnetic analysis of the Sterkfontein palaeocave deposits: implications for the age of the hominin fossils and stone tool industries

Palaeomagnetic analysis was conducted on speleothems from Members 1-5 at Sterkfontein Cave, South Africa. Palaeomagnetic analysis of siltstone and speleothem from the bulk of Member 4 indicate a reversed magnetic polarity that dates the deposits and its Australopithecus africanus fossils to between 2.58 and ∼2.16 Ma. Further confirmation of this age comes in the form of two short normal polarity events correlated to the Rèunion (∼2.16 Ma) and Huckleberry Ridge (∼2.05 Ma) events in speleothem capping the bulk of Member 4 and coeval with deposition of the final phase of Member 4, including A. africanus fossil Sts 5. At ∼2.16-2.05 Ma, Sts 5 is the youngest representative of A. africanus yet discovered. Palaeomagnetic analysis of the Silberberg Grotto deposits identifies a single short geomagnetic field event in flowstone overlying the StW 573 Australopithecus fossil, which is suggested to represent the Rèunion event at ∼2.16 Ma. This further supports the uranium lead age estimates of 2.3-2.2 Ma for the StW 573 fossil. Based on a reversed polarity for the deposits below the skeleton it cannot be older than 2.58 Ma. If StW 573 is considered to be a second species of Australopithecus then this indicates that two species of Australopithecus are present at Sterkfontein between 2.6 and 2.0 Ma. All of the Member 5 deposits date to less than 1.8 Ma based on a comparison of palaeomagnetic, faunal, and electron spin resonance age estimates. The StW 53 fossil bearing infill (M5A) is intermediate in age between Member 4 and the rest of Member 5 (B-C) at around 1.78-1.49 Ma. The rest of Member 5 (B-C) containing Oldowan and Acheulian stone tools and Homo and Paranthropus fossils was deposited gradually between 1.40 and 1.07 Ma, much younger than previously suggested.     

Long-term upwelling evolution in tropical and equatorial Pacific during the last 800 kyr as revealed by coccolithophore assemblages

The coccolithophore assemblages in two ODP Sites (1237 and 1238) are studied in order to reconstruct the paleoenvironmental conditions in the tropical and equatorial Pacific during the last 800 kyr. Both ODP Sites are located in the two most significant upwelling zones of the tropical and equatorial Pacific: Peru and Equatorial upwelling, respectively. The two sites are considered to have had similar evolutions. The coccolith relative abundance, the nannofossil accumulation rate (NAR) and the N ratio (namely, the proportion of < 3 μm placoliths in relation to Florisphaera profunda) allow us to identify three different intervals. Interval I (0.86-0.45 Ma) and interval III (0.22-0 Ma) are related to weak upwelling and weak Trade Winds, as suggested by coccolithophore assemblages with low N ratios. Interval II (0.45-0.22 Ma), characterized by dominant Gephyrocapsa caribbeanica and very abundant “small” Gephyrocapsa and Gephyrocapsa oceanica, is conversely related to intense upwelling and enhanced Trade Winds.     

Upper Permian coral reef and colonial rugose corals in northwest Hunan, South China

Summary The roles of Permian colonial corals in forming organic reefs have not been adequately assessed, although they are common fossils in the Permian strata. It is now known that colonial corals were important contributors to reef framework during the middle and late Permian such as those in South China, northeast Japan, Oman and Thailand. A coral reef occurs in Kanjia-ping, Cili County, Hunan, South China. It is formed by erect and unscathed colonies ofWaagenophyllum growing on top of one anotherin situ to form a baffle and framework. Paleontological data of the Cili coral reef indicates a middle to late Changhsing age (Late Permian), corresponding to thePalaeofusulina zone. The coral reef exposure extends along the inner platform margin striking in E-S direction for nearly 4 km laterally and generally 35 to 57 m thick. The Cili coral reef exhibits a lateral differentiation into three main reef facies; reef core facies, fore-reef facies, and marginal slope facies. The major reef-core facies is well exposed in Shenxian-wan and Guanyin-an sections where it rests on the marginal slope facies. Colonial corals are dispersed and preserved in non-living position easward. Sponges become major stabilizing organisms in the eastern part of Changhsing limestone outcrop in Kanjia-ping, but no read sponge reefs were formed. Coral reefs at Cili County in Human are different distinctly from calcisponge reefs in South China in their palaeogeography, lithofacies development, organic constitutuents, palaeoecology and diagenesis. The Cili coral reef also shows differences in age, depositional facies association, reef organisms and diagenesis from coral reefs in South Kitakami of Japan, Khorat Plateau of Thailand, and Saih Hatat of Oman. Although some sponge reefs and mounds can reach up to the unconformable Permian/Triassic boundary, coral reef at Kanjia-ping, Cili County, is the latest Permian reef known. This reef appears to had been formed in a palaeoenvironment that is different from that of the sponge reefs and provides an example of new and unique Permian reef type in South China, and could help us to: 1) understand the significance of colonial corals in Permian carbonate buildups; 2) evaluate the importance of coral community evolution prior to the collapse of reef ecosystems at the Permian/Triassic boundary; 3) better understand the effects of the biotic extinction events in Palaeotethys realm; 4) look for environmental factors that may have controlled reefs through time and space, and 5) provide valuable data for the study of Permian palaeoclimate and global evolutionary changes of Permian reefs and reef community.     

Geomorphology and Late Quaternary development of Middleton and Elizabeth Reefs

Middleton and Elizabeth Reefs are two mid-latitude, annular reefs within the Lord Howe linear chain of volcanic islands and seamounts in the southwestern Pacific Ocean. Drilling, vibrocoring, seismic profiling, and dating indicate that each has a rim of Holocene reef framework, enclosing a lagoon partly filled by prograding sand sheets composed of fragments of coral, coralline algae, foraminifers, and other skeletal debris. The reefs lie close to the latitudinal limits for coral growth and the reef framework is very porous, dominated by branching rather than massive corals. Coralline algae are the principal binding agent in the upper reef framework. Holocene reef growth began on a foundation of Pleistocene reefal limestone encountered at a depth of 8 m in cores on the windward side of Middleton Reef. Holocene corals became established on this foundation around 6,700 radiocarbon yr B.P., implying little if any lag after inundation of the platform by the post-glacial sea-level rise. Windward reef growth tracked sea-level rise (keep-up mode), and a prominent reef crest was established on both reefs by 5,000 yr B.P. Leeward margins appear to have been characterized by catch-up growth. Development of cays is limited, and has been restricted by the paucity of coarse coralline debris or cemented conglomerate on which islands could become established. The morphology and development of Middleton and Elizabeth Reefs has been similar to that of tropical atolls, although the rate of subsidence appears to have been relatively slow reflecting their position on the margin of the foundered continental crust of the Lord Howe Rise.