Academic literature on the topic 'Coral Reef Terraces'

The Kambaniru River valley near the city of Waingapu preserves a thick succession of coarse-grained fluvial-deltaic sediment deposited during the Late Pleistocene. This succession incises through a thick uplifted coral reef terrace succession and records intervals of highly episodic flow events during the last glacial interval. The occurrence of intraclastic, coarse sand/gravel matrix olistostromes in several areas attests to the occasionally catastrophic nature of flow in the ancestral Kambaniru River. Small to moderate-sized coral-rich reefs and laterally restricted reef terraces occur on delta-front conglomerate successions at multiple horizons through the study interval. These reefs record both intervals of low flow as well as periodic river-mouth avulsion episodes. Comparison of radiometric dates obtained from pelecypod and coral material from both deltaic successions and laterally adjacent coral reef terrace intervals indicates that uplift/subsidence history of the terraces differs from that of the valley and that correlation between the two should be taken with care.

AbstractAs many as six levels of emerged Holocene coral terraces occur along 40 km of coastline on the Huon Peninsula, Papua New Guinea, recording uplift history since culmination of the postglacial transgression. The Holocene reef crest, ca. 6000 yr B.P., is tilted down to the northwest, parallel to the coast and concordant with the deformation of the last interglacial coral reef terrace, and descends from 23 to 12 m in the study area. The pattern and rate of deformation have been uniform in the late Quaternary because average uplift rates have remained the same since the last interglaciation. The Holocene terraces described here are erosional features with regressive encrusting corals, developed upon the Holocene transgressive reef. The multiple levels represent episodic, probably coseismic uplift, which has occurred repeatedly in the last ca. 6000 yr. Significant longshore variation in the age of the lowest terrace, from 1700 to 2500 yr B.P., suggests independent coseismic uplift on different sectors of the coast. This is supported by age-height relationships of the higher Holocene terraces. Nonlinear uplift during the Holocene, with recurrence intervals increasing toward the present, is clearly recorded by the regressive terraces in each subregion. Some of the Holocene regressive terraces grade laterally into fluvial terraces capped with debris-flow deposits, probably reflecting seismically triggered mass movement.

AbstractCorals from raised reef terraces on two islands (Zabargad and Northern Brother), considered to have been tectonically uplifted in connection with the Red Sea rifting, were dated with the U-series method. At Zabargad, there are at least three systems of raised coral reefs. The oldest terrace (>290,000–300,000 yr B.P.) is found at +10 to +15 m. A 200,000 yr B.P. high-sea stand is recorded by a terrace relict at +17 m on peridotite bedrock; the youngest system (125,000–138,000 yr B.P.) is very well represented around the island, with terraces at about +6 to +8 m. Corals from Northern Brother yield ages of 132,000–135,000 and 204,000 yr B.P. suggesting the existence of two systems of interglacial raised reefs. Both islands appear to have been tectonically quite stable since at least 125,000 yr B.P.

The fossil record of Red Sea fringing reefs provides an opportunity to study the history of coral-reef survival and recovery in the context of extreme environmental change. The Middle Pleistocene, the Late Pleistocene, and modern reefs represent three periods of reef growth separated by glacial low stands during which conditions became difficult for symbiotic reef fauna. Coral diversity and paleoenvironments of eight Middle and Late Pleistocene fossil terraces are described and characterized here. Pleistocene reef zones closely resemble reef zones of the modern Red Sea. All but one species identified from Middle and Late Pleistocene outcrops are also found on modern Red Sea reefs despite the possible extinction of most coral over two-thirds of the Red Sea basin during glacial low stands. Refugia in the Gulf of Aqaba and southern Red Sea may have allowed for the persistence of coral communities across glaciation events. Stability of coral communities across these extreme climate events indicates that even small populations of survivors can repopulate large areas given appropriate water conditions and time.

Abstract. The primary last interglacial, marine isotope substage (MIS) 5e records on the Pacific coast of North America, from Washington (USA) to Baja California Sur (Mexico), are found in the deposits of erosional marine terraces. Warmer coasts along the southern Golfo de California host both erosional marine terraces and constructional coral reef terraces. Because the northern part of the region is tectonically active, MIS 5e terrace elevations vary considerably, from a few meters above sea level to as much as 70 m above sea level. The primary paleo-sea-level indicator is the shoreline angle, the junction of the wave-cut platform with the former sea cliff, which forms very close to mean sea level. Most areas on the Pacific coast of North America have experienced uplift since MIS 5e time, but the rate of uplift varies substantially as a function of tectonic setting. Chronology in most places is based on uranium-series ages of the solitary coral Balanophyllia elegans (erosional terraces) or the colonial corals Porites and Pocillopora (constructional reefs). In areas lacking corals, correlation to MIS 5e often can be accomplished using amino acid ratios of fossil mollusks, compared to similar ratios in mollusks that also host dated corals. Uranium-series (U-series) analyses of corals that have experienced largely closed-system histories range from ∼124 to ∼118 ka, in good agreement with ages from MIS 5e reef terraces elsewhere in the world. There is no geomorphic, stratigraphic, or geochronological evidence for more than one high-sea stand during MIS 5e on the Pacific coast of North America. However, in areas of low uplift rate, the outer parts of MIS 5e terraces apparently were re-occupied by the high-sea stand at ∼100 ka (MIS 5c), evident from mixes of coral ages and mixes of molluscan faunas with differing thermal aspects. This sequence of events took place because glacial isostatic adjustment processes acting on North America resulted in regional high-sea stands at ∼100 and ∼80 ka that were higher than is the case in far-field regions, distant from large continental ice sheets. During MIS 5e time, sea surface temperatures (SSTs) off the Pacific coast of North America were higher than is the case at present, evident from extralimital southern species of mollusks found in dated deposits. Apparently, no wholesale shifts in faunal provinces took place, but in MIS 5e time, some species of bivalves and gastropods lived hundreds of kilometers north of their present northern limits, in good agreement with SST estimates derived from foraminiferal records and alkenone-based reconstructions in deep-sea cores. Because many areas of the Pacific coast of North America have been active tectonically for much or all of the Quaternary, many earlier interglacial periods are recorded as uplifted, higher-elevation terraces. In addition, from southern Oregon to northern Baja California, there are U-series-dated corals from marine terraces that formed at ∼80 ka, during MIS 5a. In contrast to MIS 5e, these terrace deposits host molluscan faunas that contain extralimital northern species, indicating cooler SST at the end of MIS 5. Here I present a review and standardized database of MIS 5e sea-level indicators along the Pacific coast of North America and the corresponding dated samples. The database is available in Muhs et al. (2021b; https://doi.org/10.5281/zenodo.5903285).

One of the most intriguing questions in community ecology remains unanswered: Are ecological communities open assemblages with each species reacting individually to environmental change, or are they integrated units consisting of multispecies assemblages acting in concert? I address this question for marine organisms by examining the taxonomic composition and diversity of Indo-Pacific reef coral communities that have undergone repeated global change between 125 and 30 Ka (thousand years before present).Investigation of community constancy through time relies on two critical questions: (1) Are there significant differences in taxonomic composition among communities from different times? and if not, (2) Are the observed patterns in temporal similarity significantly different from expected patterns resulting from a random sampling of the available within-habitat species pool?Constancy in taxonomic composition and species richness of Pleistocene reef coral assemblages is maintained through a 95-k.y. interval in the raised reef terraces of the Huon Peninsula, Papua New Guinea. Fossil reef coral assemblages show limited membership in species composition despite repeated exposure to marked fluctuations in sea level (up to 120 m) and sea-surface temperatures (up to 6°). During the 95-k.y. interval, the reefs experienced nine cycles of perturbation and subsequent reassembly with similar species composition. Spatial differences in reef coral species composition were greater among the three study sites than among reefs of different ages. Thus local environmental parameters associated with riverine and terrestrial sources had a greater influence on reef coral composition than global climate and sea level changes.The ecological dynamics of reef communities from Papua New Guinea are in marked contrast to those of Quaternary terrestrial and level bottom marine communities which appear to show unlimited community membership on both larger and smaller time scales. Differences in community assembly among ecosystems mean either that coral reefs are fundamentally different or that different ecological patterns and processes are occurring at different temporal scales.

Batuan yang mendominasi di daerah penyelidikan adalah batugamping koral Formasi Paciran zona Rembang. Batugamping koral inilah membentuk undak pantai di Tanjung Awar-awar dan di pantai Tuban dan sekitarnya. Terdapatnya undak batugamping ini, menandakan adanya pengangkatan secara vertikal pada satuan batuan ini. Batimetri daerah penyelidikan secara umum merupakan dataran dimana bagian yang dangkal terdapat di bagian baratdaya (ke arah pantai) dengan kedalaman 2 meter dan terdalam ke arah timurlaut dengan kedalaman 9 meter. Sebanyak 7 lintasan seismik berarah timurlaut-baratdaya dan 15 lintasan berarah barat laut – tenggara telah dilakukan dan beberapa titik bor untuk memperkuat penafsiran jenis batuan di setiap lapisan penampang seismik. Struktur geologi yang ditafsirkan dari seismik pantul ini adalah adanya suatu blok batuan yang seperti tersesarkan dan terdorong ke atas sebagai struktur diapir. Struktur diapir ini berkembang sangat baik di penampang seismik ke arah barat daya atau ke arah daratan dimana di sekitar pantainya batugamping ini membentuk undak batugamping. Munculnya struktur diapir ini kemungkinannya dikarenakan bagian selatan dari zona Rembang ini terdapat suatu zona yang mempunyai anomali gaya berat negatif dan karena batugampingnya banyak terpatahkan sehingga sangat mudah diintrusi oleh sedimen yang mempunyai berat jenis kecil. Kata kunci : undak pantai, batugamping koral, struktur diapir, Tanjung Awar-Awar Jawa Timur The study area is dominated by coral reef limestone of Paciran Formation of Rembang Zone. This coral reef limestone is responsible to form the beach terraces along the Tanjung Awar-Awar and Tuban beach and its surrounded. The formation of this coral reef limestone terraces closely related to vertical movement of these rocks units. The study area is bathymetrically flat where the shallow part is on southwest (towards the beach) with 2 meters depth and the deeper part is to northeast part with 9 meters depth. There are 7 seismic reflection lines of NE-SW and 15 lines of NW-SE have been done and some rocks drilling to emphasize the seismic sequences. The interpretation of geological structure from seismic reflection shows a feature of rocks unit was faulted and intruded as diapiric structures. These features are well developed towards the beach where the terrace of coral reef limestone can be found on the beaches. The formation of these diapiric structures are interpreted where on southward of the Rembang Zone there is a gravity negative anomalies and also due to the limestone were faulted and it seems to be easy intruded by a sediment with low density. Keywords : beach terraces, coral reef limestone, diapiric structure, Tanjung Awar- Awar East Java

ABSTRACT Barbados is actively rising in the latest phase of a long history of emergence that began as far back as 15 Ma. The current phase began at or before ca. 700 ka, is highly nonuniform, and at least locally, has been nonsteady. The uplift rate field in SE Barbados ranges between near-zero and 0.47 m/k.y. and is harmonic to active structures of NNW-SSE contraction. Emergence markers include limestone strata, coral, and shoreline angles, but we used only shoreline angles in calculations. We divided the capping limestone of windward Barbados into 10 units using physical criteria and dated them with over 40 230Th ages as oxygen isotope stages 5a, 5e, late 7 and early 7, and old (older than 300 ka). The oldest unit is a relic of an earlier phase of emergence. Younger units, probably as old as 700 ka, downlap the eroded flank of the oldest unit and sublimestone foundation. Younger units comprise landward clastic facies deposited on abrasion platforms during eustatic highstand and seaward-coalescent fringe reef blankets deposited on preexisting slopes, mainly in transgression. Earlier models of ridged reefs of catch-up growth origin are not supported in windward Barbados. Shoreline angles, the updip tips of terrace floors and of younger limestone units, are isochronous markers of maximum highstand levels. Despite the lack of direct determination of their ages, shoreline angles provide the truest measures and highest values of emergence. Coral thought to indicate highstand growth gives moderately lower uplift rates due to depths of growth and collapse. Coral grown during transgression gives a marked error in emergence.