Abstract Paleozoic reefs were first identified by James Hall (1862) in the Silurian rocks of the American Midwest. Scientifically, they were crucial in defining ancient reefs, documenting the early history of this marine ecosystem, and interpreting regional stratigraphy, palaeogeography and palaeoecology. Schoonmaker Reef in Wauwatosa, Wisconsin, is historically the most significant of these structures, as the first to be correctly identified as a ‘coral’ reef by exhibiting the transition between a reef mound and the surrounding seafloor. After nearly two hundred years of quarrying, Thornton Reef in Thornton, Illinois, is next in importance as it displays an unequalled three-dimensional exposure, demonstrating the impact of Silurian climate change on reef development. Silurian reefs were discovered and studied only through stone industry quarrying. Extensive nineteenth-century fossil collecting by local naturalists was also a key component in reef studies. These reefs are also an important part of the region's geoheritage, comprising elements of its economy, history, education and scenic landscape. Recognizing their scientific and historical importance, some reefs were part of geoconservation projects and are protected sites. However, other reefs and irreplaceable reef fossil collections need further initiatives to preserve the scientific value and historical legacy of these relatively small geological features.

Abstract The Falls of the Ohio is a world-renowned geoheritage site of palaeontological and geological importance that also played key roles in the cultural and historical development of America. Studied by geologists for over two centuries, over 600 species of fossils are known from the site, hundreds of which were first described here. Beyond geology, the Falls of the Ohio can also be considered the origin and ending of the Lewis and Clark expedition, as well as an important location for naturalists and educators. A treasure of natural and human history and a National Natural Landmark, this spectacular 220 acre (89 ha) expanse of fossiliferous bedrock is worthy of ongoing study and protection.

Abstract Line Intercept Transects (LIT), Point Intercept Transects (PIT) and Photoquadrats (PQ) are the most common quantitative sampling techniques in modern and fossil coral reefs. Data from coral reefs obtained by the different methods are generally compared between various reef ages and localities. Quaternary reefs from warmer interglacial periods, which represent climate scenarios projected for the future, are particularly interesting for comparisons with modern reefs. Importantly, fossil reefs differ from modern reefs because they are diagenetically altered and time-averaged. While several studies have compared different quantitative methods in modern reefs, very few have dealt with the comparability among fossil and between fossil and modern reefs. Here, we compare LIT, PIT at 10, 20 and 50 cm intervals and PQ in two Pleistocene reef localities in Egypt. We find that alpha diversity, reef cover and community composition are dependent on the method. Results gained with plotless methods (LIT, PIT) differ strongly from results gained with plot methods (PQ). However, coral cover results are similar with LIT and PIT, and community composition is indistinguishable between the two, but alpha diversity depends on the interval used for PIT. We discuss the implications of our findings for comparing coral reefs of various ages and localities. We recommend surveying Pleistocene reefs with PIT at 20 cm intervals. This is because (1) alpha diversity is well captured, (2) the amount of time-averaging recorded by PIT is reduced compared to PQ, (3) the PIT results can be directly compared to reefs analysed by LIT and (4) the method is less time-consuming than LIT and PQ.

This paper presents a brief synopsis of the Miocene Epoch, an important transitory chapter in the history of the Earth. It was during the Miocene that the major continents and oceans attained a “modern” configuration in terms of paleogeography and tectonics, oceanic ventilation and circulation, ocean chemistry, and faunal and floral assemblages. It also was during the Miocene that global climate fully transitioned into its current icehouse state, including marked growth of the Antarctic ice sheet and initiation of the Arctic ice cap. Long-term global cooling was controlled by a number of factors including tectonics, the large-scale changes in the distribution of flora, particularly the expansion of grasslands, and by fluctuating orbital parameters of the Earth. This global cooling trend was briefly interrupted by a short period of warming in the middle Miocene. Miocene sea-level changes consisted of a number of glacio-eustatic third-order (1–5 million year [m.y.] duration) cycles superposed upon three longer-term, second-order (5–20 m.y. duration) supercycles. Development of large-scale tropical carbonate systems in the Miocene was relegated to three main geographic regions: the circum-Caribbean, Mediterranean, and Indo-Pacific. In addition, a pronounced cool-water platform system developed along the southern margin of Australia. Miocene reefal buildups were dominated by tropical to subtropical framework assemblages consisting primarily of large scleractinian corals, encrusting red algae, and rhodoliths (free-living coralline red algae) that grew on platform margins and interiors or on isolated atolls. Miocene carbonates were deposited in a variety of oceanic and structural settings and constitute important petroleum reservoirs, particularly in Southeast Asia. Deep-water terrigenous clastic sediments of Miocene age are also important petroleum reservoirs in some regions. In addition, the Miocene interval contains numerous prolific petroleum source rocks, most composed of Type III (gas-prone) kerogen.

A new compilation of data suggests aragonitic coral reefs were already common in Southeast Asia by the mid-Oligocene. A gradual change from calcite to aragonite seas through the Oligocene and early Miocene appears to be related to a gradual expansion of the importance of scleractinia, along with green algae and mollusks, and an associated decline in the abundance of calcitic larger foraminifera. The larger foraminifera had been important rock-forming bioclasts in the early part of the early Miocene, but were a minor component of carbonate faunas by the end of the middle Miocene. This gradual decline in abundance included a few extinction events that reduced diversity, and these extinctions appear to correlate with periods of tectonic change. The K-selection evolutionary pressure impacted carbonate facies, but foraminifera maintained their taxonomic diversity until the abrupt faunal extinctions. Changes in sea-surface temperature, or the regional change from seasonal to ever-wet climate, do not appear to have impacted larger foraminiferal diversity or caused extinctions, only modified their latitudinal range. Some extinction events can be recognized across the whole Tethys Ocean, as can some of the times of tectonic activity and possible climate change. These correlations tentatively point to a link between large-scale changes in plate motion, oceanography, and foraminiferal extinctions. In contrast, the change from seasonal to ever-wet conditions around the Oligo–Miocene boundary around the South China Sea does not appear to have been caused by a wider tectonic event, and this event does not impact larger foraminifera diversity. A combined tectonic unconformity and mass extinction of larger foraminifera in middle middle Miocene times might have been due to the plate tectonic constriction of a throughflow between the Pacific and Indian Oceans.

Remote-sensing analysis of high-resolution satellite imagery of modern carbonate platforms in the Celebes Sea, east of Sabah, Borneo, Malaysia, was used to map geomorphology and sediment. Unsupervised classification of satellite images was interpreted in the context of environmental facies of seven isolated carbonate platforms and calibrated using analyses of surface sediments. In total, 140 sediment samples were collected and analyzed for grain-size and sorting. The grain-size analysis showed that sediment varied among the geomorphic elements, which included island, island/volcano, reef complex, carbonate sand shoal, grass-covered sand shoal, shallow lagoon, and deep lagoon. To generate carbonate sediment texture maps, the proportion of mud and the grain-size attributes (mean grain size and sorting) of each sediment sample provided a basis to classify samples into rock-equivalent textures. Integration of remote-sensing, field, and sedimentological data provided a means to characterize texture distribution maps and depositional facies maps. These maps suggest that mudstone to wackestone occurs mainly in the deep lagoon; wackestone to packstone is dominant in the shallow lagoon; the carbonate sand shoal is characterized by packstone to grainstone; and the reef complex is made up of boundstone to rudstone. These results facilitate estimates of the proportions of potential reservoirs on these platforms and the heterogeneity in facies distribution, based on the size of various recent carbonate platforms. Diagenesis notwithstanding, ancient analogs indicate the Selakan and Maiga platforms could be potential reservoirs, whereas the Selakan and Gaya platforms display more facies classes and represent poor potential reservoirs.

Shallow marine mixed siliciclastic–carbonate shoals, a carbonate platform, and the subsequent development of a reefal buildup occur in sequence from the late Chattian to the Aquitanian in the Niah area of Sarawak. They document the transition from larger foraminifera-dominated, calcitic environments to scleractinian coral–dominated, aragonitic environments in SE Asia, which correspond to a significant increase in biodiversity. A late Chattian to early Aquitanian phase of carbonate sedimentation was initiated by larger foraminifera on shallow marine argillaceous shoals raising from the seabed at about 60 m in water depth occasionally up to near sea level. Carbonate production is almost entirely the result of the accumulation of larger foraminiferal shells dominated by Eulepidina dilatata , a species that could thrive thanks to its photosymbiosis with microalgae. Such mixed carbonate–clastic shoals formed repeatedly on a muddy shelf during a period stretching from about 23.5 Ma to 22.3 Ma. Following a period of siliciclastic deposition, a roughly circular carbonate platform with an area of some 25 km 2 was formed at around 21.2 Ma in stratigraphic continuity with the underlying shallow marine sandstones of the Nyalau Formation. Known as the Subis Limestone, it consists at first of bedded carbonates characterized by the presence of red algae, a high diversity of free benthic and sessile endosymbiotic sessile foraminifera, and a variety of organisms typical for reefal environments, including colonial corals. A reefal buildup started forming on the carbonate platform as early as 21.1 Ma. This phase of growth was likely initiated by low-relief patch reefs, 150 to 200 m in diameter and 60 to 80 m in height, such as those exposed in a southern quarry. Analogous with same-age reefal development models from the Java Sea, it is proposed that the patch reefs coalesced through time to form a larger isolated carbonate buildup that grew up at least until the end of the Aquitanian at 20.4 Ma. This Subis buildup reached an area of 16 km 2 ; it has a preserved thickness of 260 to 280 m and had a paleo-relief of about 100 m above the surrounding sea floor. It is asymmetrical, with a reef wall forming high, west-facing cliffs and another reef wall likely extending on the NE edge of the buildup, beyond the Niah Great Cave. A further increase in faunal and floral diversity occurred during this phase, concomitant with the diversification of ecological niches within the buildup. Reefal and peri-reefal environments are dominated by red algae; solitary and colonial corals (domal, branching, and platy), with subordinate foraminifera (large and small benthic); and associations of foraminifera and algae forming laminar foralgal binding tissues, sponges, hydrozoans, bryozoan, bivalves, echinoderms, and serpulids. The reef rim consists of coral framestone and algal-foraminiferal bindstone. The backreef facies is characterized by rudstones and floatstone with coral debris, and the lagoon facies includes microbial crusts, green algae, articulated and nonarticulated red algae, benthic foraminifera ( Miliolids ), ostracods, gastropods, and up to 4-m-high platy corals pillars. Forereef deposits include grain- and mud-supported reef debris; a debris apron present some 2.5 km away from the western edge of the buildup consists of debris flows and calciturbidites embedded in outer neritic shales. The upper part of the buildup is missing as a result of recent subaerial erosion. Three successive steps in the development of carbonate ecosystems are identified, which are linked to a series of innovative symbiotic relationships established during the late Chattian and the Aquitanian. During an early phase (23.5–22.3 Ma), monospecific populations of endosymbiotic larger benthic foraminifera thrived on shallow marine muddy shoals. At around 21.2 to 21.1 Ma, new species of endosymbiotic larger benthic foraminifera, sessile-encrusting foraminifera, and coralline algae colonized shallow marine grounds and created a carbonate platform. From about 21.1 to at least 20.4 Ma endosymbiotic scleractinian corals, red algae, and a diverse association of organisms created patch reefs and a buildup.