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1.
Summary Reef facies, reef types and their biotic associations in the Maiella platform margin (central Italy) provide qualitative evidence
for a significant reef decline across the Cretaceous/Tertiary (K/T) boundary, and indicate two phases of reef recovery during
the Paleocene. Rudists dominated the reef community until the latest Cretaceous. A significant sea-level fall around the time
of the K/T boundary is documented by a truncation surface associated with emersion.
During sea-level highstands in the Danian to Early Thanetian and, more extensively, during the Late Thanetian, coral-algal
patch-reefs grew along the platform margin and top. Already in the Danian to Early Thanetian, the reef communities were more
diverse and the constructional types more evolved than previously known from this time. Differences between the Danian to
Early Thanetian coral association, the Late Thanetian association, and Late Cretaceous coral faunas may have ecological or
evolutionary causes.
Repeated emergence produced a complex diagenetic history in the Danian to Lower Thanetian limestones. All Paleocene reefs
were displaced by gravitative redeposition. Coral-algal reefs are less important in the Early to mid Eocene, when alveolinid
foraminifera dominated on the Maiella shelf. Reefs on the Maiella platform diversified and attained large sizes in the Late
Eocene to Early Oligocene, as known from other Mediterranean platforms.
The external controls on the Late Cretaceous to Oligocene evolution and demise of reef communities that are most easily demonstrated
with our data are sealevel fluctuations and climate change. We propose that the change in reef biota and reef types across
the K/T boundary and during the Early Tertiary were important causes of the parallel changes in platform growth style. 相似文献
2.
Summary Givetian to early Carboniferous sediments of South China are characterized by carbonates. Middle and Late Devonian strata
are best developed in the Guilin area. Reefs and organic shoals are recorded by various lithofacies types indicating the existence
of an extended carbonate platform and a change of the composition of reef communities in time. Starting in the late Devonian,
stromatoporoids and corals were replaced by algae that subsequently played an important role together with stromatoporoids,
receptaculitids and fasciculate rugose corals in reef communities. In Houshan, 5 km west of Guilin, a coral-bafflestone reef
occurs in the Frasnian strata, situated near an offshore algal-stromatoporoid reef. The coral reef was formed in a back-reef
area adjacent to the inner platform margin. The coral-bafflestone reef is unique among the late Devonian reefs of South China
with regard to the biotic composition. The reef is composed of fasciculate colonies ofSmithiphyllum guilinense n. sp. embedded within in packstones and wackestones. The height of colonies reaches 1 m. The community is low-diverse. The
species ofSmithiphyllum occurring in the Frasnian reef complexes of Guilin exhibit a distinct facies control:Smithiphyllum guilinense occurs in or near to margin facies and formed bafflestone, constituting a coral reef whereasSmithiphyllum occidentale
Sorauf, 1972 andSmithiphyllum sp.—characterized by small colonies with thin corallites—are restricted to the back-reef and marginal slope facies. The bush-like
coral colonies baffled sediments. Algae and stromatoporoids (mainlyStachyodes) are other reef biota. Reef-dwelling organisms are dominated by brachiopods.
The reefs are composed from base to top of five lithofacies types: 1) cryptalgal micrite, 2) peloidal packstone, 3) stromatactis
limestone, 4) coral-bafflestone, and 5) pseudopeloidal packstone. The reef complex can be subdivided into back-reef subfacies,
reef flat and marginal subfacies, and marginal fore-slope subfacies. The Houshan coral-bafflestone reef is not a barrier reef
but a coral patch reef located near the inner margin of a carbonate platform. 相似文献
3.
Carbonate breccias in the lower-middle Ordovician Maggol Limestone (Taebacksan Basin,South Korea): Implications for regional tectonism 总被引:1,自引:0,他引:1
Summary Carbonate breccias occur sporadically in the Lower-Middle Ordovician Maggol Limestone exposed in the Taebacksan Basin, South
Korea. These carbonate breccias have been previously interpreted as intraformational or fault breccias. Thus, little attention
has been focused on tectonic and stratigraphic significance of these breccias. This study, however, indicates that the majority
of these breccias are solution-collapse breccias, which are causally linked to paleokarstification.
Carbonate facies analysis in conjunction with conodont biostratigraphy suggests that an overall regression toward the top
of the Maggol Limestone probably culminated in subaerial exposure of platform carbonates during the early Middle Ordovician.
Extensive subaerial exposure of platform carbonates resulted in paleokarst-related solution-collapse breccias in the upper
maggol Limestone. This subaerial exposure event is manifested as a major paleokarst unconformity elsewhere beneath the Middle
Ordovician sequence, most notably North America and North China. Due to its global extent, the early Middle ordovician paleokarst
unconformity (‘the Sauk-Tippecanoe sequence boundary’) has been viewed as a product of second-order eustatic sea level drop
during the early Middle Ordovician. Although we recognizes a paleokarst breccia zone in the upper Maggol Limestone beneath
the Middle Ordovician sequence, the early Middle Ordovician sequence boundary appears to be a conformable transgressive surface
or a drowning unconformity, rather than a major paleokarst unconformity. The paleokarst breccia zone in the upper Maggol Limestone
is represented by a thinning-upward stack of exposure-capped tidal flat-dominated cycles that are closely associated with
multiple occurrences of paleokarst-related solution-collapse breccias. The paleokarst breccia zone in the upper Maggol Limestone
was a likely consequence of repeated high-frequency sea level fluctuations of fourth- and fifth-order superimposed on a second-and
third-order eustatic fall in sea level that was less than the rate of tectonic subsidence across the platform. It suggests
that second- and thirdorder eustatic sea level drop may have been significantly tempered by substantial tectonic subsidence
near the end of maggol deposition. The tectonic subsidence in the basin is also evidenced by the occurrence of coeval off-platform
lowstand siliciclastic quarzite lenses as well as debris flow carbonate breccias. With the continued tectonic subsidence,
subsequent rise in the eustatic cycle caused drowning and deep flooding of carbonate platform, forming a conformable transgressive
surface or a drowning unconformity on the top of the paleokarst breccia zone. This tectonic implication contrasts notably
with the slowly subsiding carbonate platform model for the Taebacksan Basin as previously intepreted. Here we propose that
the Taebacksan Basin evolved from a slowly subsiding carbonate platform to a rapidly subsiding intracontinental rift basin
during the early Middle Ordovician. This study also provides a good example that the falling part of the eustatic sea-level
cycle may not produce a significant event at all in a rapidly subsiding basin where the rate of eustatic fall always remained
lower than the rate of subsidence. 相似文献
4.
A new concept, termed ‘Facies Dynamics’ (defined as changes of specific carbonate facies types in time and space, which are controlled by phylogenetic, ecological and geological parameters), is introduced. This concept aims to define and interpret spatial and temporal changes of carbonate facies patterns. It is based on Middle Eocene to Early Oligocene shallow-water carbonate facies types from the circumalpine area (north-eastern Italy, northern Slovenia, Austria and southern Bavaria), which are compared with respect to dominating biogenic components and their distributions along a shelf gradient. This comparison has lead to the distinction and definition of 14 Major Facies Types (MFTs), which are dominated by coralline algae, larger and smaller foraminifera, corals and bryozoans. The presence and distribution of these MFTs from three different time slices (Middle Eocene, Late Eocene and Early Oligocene) is compared. Nine aspects of facies dynamics are distinguished: origination, extinction, immigration, emigration, expansion, reduction, stasis, shift, and replacement of MFTs. These changes are controlled by regional changes in ecological parameters, but also by global events, especially extinction patterns at the Middle/Late Eocene boundary and at the Eocene/Oligocene boundary. 相似文献
5.
6.
Dr. Francesca R. Bosellini 《Facies》1998,39(1):203-225
Summary During the Late Eocene, shelf-edge patch reefs developed on the western margin of the Lessini Shelf. The coral fauna, studied
in the Nago Limestone type locality, is described and interpreted for the first time, and provides further data for better
understanding of the generally poorly known Eocene reef communities.
Facies analysis was carried out across the shallowing upward succession that characterizes the well exposed type-section of
the Nago Limestone. Four distinct facies are identified and a detailed qualitative-quantitative investigation has been applied
to the coral-bearing facies in particular, in order to describe and quantify the distribution and palaeoecological zonation
of corals.
By a comparison of sedimentological and palaeoecological data, it is possible to reconstruct a depositional model of the Nago
Limestone at its type locality. In particular, the palaeoecological study clearly reveals that corals change with depth in
taxonomic composition, in percentage and proportion within the framework and in growth form, allowing the definition of a
relative depth coral zonation.
Three coral associations are recognized from the base to the top of the shallowing upward sequence. These differ from each
other in the relative abundance of main reefbuilders, in the growth form exhibited by corals in growth position and in the
density of the reef framework. These variations are interpreted as responses to major environmental controls which prevailed
during the deposition of the different facies (mainly light intensity and hydrodynamic energy).
The coral speciesActinacis rollei
Reuss is the most abundant and ubiquitous coral of the Nago Limestone. Its adaptation to low-light levels is described here for
the first time, confirming the high plasticity of this important Paleogene reef-builder.
The results of the present study are finally compared with data from other Middle-Late Eocene European reef sites and some
common features are inferred. 相似文献
7.
Summary The Upper Rhaetian coral limestone of Adnet, southeast of Salzburg Austria has been repeatedly referred to as one of the most
spectacular examples of an ancient ‘autochthonous’ coral reef structure. The ‘Tropfbruch’ quarry is probably the best outcrop
for interpreting the distributional patterns of biotic successions and communities of a late Triassic patch reef. Our study
is based on the interpretation of a) outcrop photographs, b) reef maps resulting from quadrat transects, and c) the analysis
of quantitative data describing the distribution and frequency of reef organisms and sediment. A new methodological approach
(combination of reef mapping and photo-transects) is used to obtain quantitative field data which can be compared in greater
detail with data from modern coral reefs investigated by corresponding quantitative surveys.
Three unconformities and three well-defined ‘reef growth stages’ reflecting the vertical and lateral development of the reef
structure were differrentiated using transects:
Stage 1, representing the reef growth optimum, is characterized by laterally differentiated coral reef knobs with corals in
growth position. Criteria supporting this interpretation are the extraordinary size of the corals, their preservation in situ
and the great thickness of this interval. The massive coralPamiroseris grew under higher energy conditions at the rim of the reef knob, whereas branchingRetiophyllia colonies preferred less agitated water in the center. Vertical changes are reflected by an increase in frequency of the dasycladacean
algaDiplopora adnetensis and by the decreasing size ofRetiophyllia. These sedimentological and biological criteria together with the unconformity above indicate a fall in the sea level as
a major control mechanism.
Stage 2, separated from stage 1 by an unconformity caused by partial subaerial exposure and karstification, is characterized
by vertically stacked coral successions with diverse reef debris. Facies heterogeneity is reflected by differences in the
diversity, taphonomy and packing density of reef-building organisms as well as by differences in sediment input from the platform.
Water depths and accommodation space were lower, therefore minor sea level fluctuations had a stronger effect on the biotic
composition. The high percentage of coral debris and corals reworked by storms and the increase in the input of platform sediment
led to a reduction of reef growth.
Stage 3, again separated at the base by an unconformity associated with karstification, is characterized by bioclastic sediments
with isolated reefbuilders forming a level-bottom community. The distribution of different coral morphotypes suggests that
sea level fluctuations were not the only controlling factor. Variations in the substrate were caused by differences in the
input of platform sediment.
The three-step development seen in Adnet documents the response of low-diverse coral associations to variations caused by
small-scale sea level changes, storm activity and sedimentation. The vertical changes in reef community structures correspond
to a sequence of ‘allogenic replacements’.
The Adnet reef structure should not be regarded as a general model of Alpine Upper Rhaetian reefs, because of the particular
setting of the patch reef. Only the ‘capping beds’ of the Upper Rhaetian Reef Limestone of the Steinplatte exhibit criteria
similar to Adnet.
Potential modern analogues of features seen in the coral communities of Adnet are the internal structure of theRetiophyllia thickets, the key role of branching corals within the communities, the scattered distribution and low and even diversity
of corals subsequent to breaks in settlement, segration patterns of corals indicating ‘contact avoidance’, toppling of large
coral colonies by intensive boring, and decreasing coral coverage from deeper and sheltered settings to more shallower water
depths. 相似文献
8.
《Annales de Paléontologie》2020,106(2):102383
A new occurrence of the Palaeocarpilius macrochelus (Desmarest, 1822) (Crustacea: Decapoda: Brachyura), from the Middle Oligocene rocks of the United Arab Emirates is systematically and paleogeographically described. The Oligocene Asmari Formation is well exposed on the flanks of Jabal Hafit anticline near Al Ain City, UAE, and represents one of the very interesting fringing reef complex outcrops at the western margin of the Northern Oman Mountains. A relatively well preserved single specimen was collected from the Asmari Formation of Jabal Hafit. The specimen is herein described and assigned to Palaeocarpilius macrocheles (Desmarest, 1822). The present record complements the information on the temporal and spatial distribution of decapods at the southern margin of the Tethyan Ocean during the Middle Oligocene times. 相似文献
9.
Ramp morphology controlling the facies differentiation of a Late Ordovician reef complex at Bachu,Tarim Block,NW China
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Yuanyuan Zhang Jianpo Wang Axel Munnecke Yue Li 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2015,48(4):509-521
A carbonate ramp in the shallow‐marine northwestern part of the Central Tarim Uplift, Bachu, NW China, exhibits an extraordinary Late Ordovician reef complex along the Lianglitag Mountains, exposed for a distance of about 25 km. Seven localities within the ‘Middle Red Limestone’ of the Upper Member of the Lianglitag Formation (Katian, Late Ordovician) illustrated the changes in biofacies and lithofacies: northern, seaward‐directed patch reefs are replaced towards the south by coeval grain banks. The patch reef units are dominated by microbial and calcareous algal components. The reefs at the northernmost locality are knoll‐shaped, kalyptra‐shaped or irregularly shaped with sizes of individual reefs increasing from about 2 m in height and diameter. Stratigraphically upward, reefs notably expand to larger structures by several mounds coalescing; they are generally about 10 m thick and tens of metres in lateral extent. The maximum thickness of the main patch reef is more than 30 m, and its diameter is around 100 m. The reefal units turn into biostromes with gentler relief southward and still further south grade into banks composed of peloids and coated grains. The southernmost locality is still a shallow‐water bank, and the coastline is not documented in the study area. The present evidence indicates that the Late Ordovician palaeo‐oceanography provided a number of environments for the optimal growth of carbonate build‐ups; microbial‐calcareous algal communities could thrive in areas where the innovative metazoan reef frameworks consisting of corals and stromatoporoids did not play a significant role. The ramp morphology, especially changes in water depth, controlled the configuration of the reef complex. 相似文献
10.
Reefal units in the early to middle Miocene of Anguilla consist of small, irregular lenses of variable coral composition which developed on a shallow, isolated offshore carbonate platform. They are composed of three distinct coral biofacies (branched, mound-shaped, and platy), which are haphazardly distributed in association with inter-reef sands. These units most probably formed as patch reefs across a broad, shallow area that was exposed to moderate energy conditions and periodically affected by storms. No evidence supports the existence of a more extensive barrier reef system. Comparisons with Oligocene and Mio-Pliocene reefs suggest that during the early to middle Miocene, Caribbean reefs were generally smaller in size (<100 m3) and lower in diversity (21 species in Anguilla, 42 species in total across the Caribbean) than Caribbean reefs during the late Oligocene or during the ate Miocene to early Pliocene (71 species in the Dominican Republic, 80 species total across the Caribbean). The early to middle Miocene Caribbean reef coral fauna was dominated by nine widespread species that occur in deposits of similar age in both Anguilla and Panama. More than half of the fauna consisted of Oligocene relicts. Of the 21 genera that first appeared in the Caribbean during Miocene time, 14 had first occurrences after the middle Miocene, as barrier reef systems became more prevalent across the central Caribbean. 相似文献
11.
Damien Pas Anne-Christine Da Silva Pierre Cornet Pierre Bultynck Peter Königshof Frédéric Boulvain 《Facies》2013,59(4):969-990
The Brilon-reef complex is one of the biggest Devonian carbonate buildups (~80 km2) of the Rheinisches Schiefergebirge. The Burgberg section is located in the southeastern fore-reef area of the Brilon Reef Complex and exposes a succession of strata (117 m thick), which extends from the Middle Givetian (middle varcus conodont Zone) to the Viséan (bilineatus conodont Zone). Field and microfacies observations led to the definition of nine microfacies that are integrated into a sedimentary model divided into off-reef, intermediate fore-reef, and proximal fore-reef sedimentary domains (SD). The off-reef domain (SD1) is the most distal setting observed and is characterized by fine-grained sediments, dominated by pelagic biota and the local occurrence of gravity-flow deposits. The intermediate fore-reef (SD2) is characterized by a mixture of biota and sediments coming from both deeper-water and shallow-water sources and is influenced by storm and gravity-flow currents. In this domain, Renalcis mound-like structures developed locally. Finally, the proximal fore-reef (SD3) corresponds to the most proximal setting that is strongly influenced by gravity-flow currents derived from the Brilon Reef Complex. The temporal evolution of microfacies in the fore-reef setting of the Burgberg section show five main paleoenvironmental trends influenced by the onset, general development, and demise/drowning of the Brilon Reef Complex. Fore-reef to off-reef lithologies and their temporal changes are from the base to the top of the section: (U1)—fine-grained sediments with large reef debris, corresponding to the initial development of the reef building upon submarine volcaniclastic deposits during the Middle Givetian (middle varcus Zone) and first export of reef debris in the fore-reef setting; (U2)—high increase of reef-derived material in the fore-reef area, corresponding to a significant progradation of the reef from the Middle Givetian to the Early Frasnian (maximum extension of the Brilon Reef Complex to the south, disparilis to the falsiovalis conodont biozones); (U3)—progressive decrease of shallow-water derived material and increase of fine-grained sediments and deep-water biota into the fore-reef setting, corresponding to the stepwise withdrawal of the reef influence; from the Middle to the Late Frasnian (jamieae conodont Zone); (U4)—development of a submarine rise characterized by nodular and cephalopod-bearing limestones extending from the Late Frasnian to the Late Famennian corresponding to the demise and drowning of the Brilon Reef Complex as a result of the Late Frasnian Kellwasser events (upper rhenana and triangularis conodont biozones); (U5)—significant deepening of the Burgberg area starting in the Late Famennian, directly followed by an aggrading trend marked by pelagic shales overlying the nodular limestone deposits. 相似文献
12.
Summary An integrated study of the early Messinian reef complex cropping out along the eastern coast of the Salento Peninsula (southern
Italy), including stratigraphy, facies analysis and paleoecological aspects, is here presented. Fourteen facies types belonging
to three main facies associations (back reef and shelf, shelf-edge, slope) have been recognized. They document a wide spectrum
of depositional environments, reef building organisms and growth fabrics, in response to depth and other environmental factors
in different parts of the reef complex.
The biotic structure of the reef is also described and discussed in detail. It consists of different types of reef building
organisms and of their bioconstructions (mainlyPorites coral reefs,Halimeda bioherms and vermetidmicrobial “trottoirs”), that differ in composition and structure according to their position on the
shelf edge-toslope profile.
Results indicate that the reef complex of the Salento Peninsula has strong similarities with the typical early Messinian reefs
of the Mediterranean region. However, the recognition of some peculiar features, i.e. the remarkable occurrence ofHalimeda bioherms and of vermetid-microbial “trottoirs”, gives new insights for better understanding reef patterns and development
of the reef belt during the Late Miocene in the Mediterranean. 相似文献
13.
Franz T. Fürsich Markus Wilmsen Kazem Seyed-Emami Gerhard Schairer Mahmoud R. Majidifard 《Facies》2003,48(1):171-198
Summary Following a phase of predominantly siliciclastic sedimentation in the Early and Middle Jurassic, a large-scale, low-latitude
carbonate depositional system was established in the northern part of the Tabas Block, part of the central-east Iranian microplate,
during the Callovian and persisted until the latest Oxfordian/Early Kimmeridgian. Running parallel to the present eastern
block margin, a NNW/SSE-trending carbonate platform developed in an area characterized by reduced subsidence rates (Shotori
Swell). The growth of this rimmed, flat-topped barrier platform strongly influenced the Upper Jurassic facies pattern and
sedimentary history of the Tabas Block. The platform sediments, represented by the predominantly fine-grained carbonates of
the Esfandiar Limestone Formation, pass eastward into slope to basin sediments of the Qal'eh Dokhtar Limestone Formation (platform-derived
allochthonites, microbialites, and peri-platform muds). Towards the west, they interfinger with bedded limestones and marlstones
(Kamar-e-Mehdi Formation), which were deposited in an extensive shelf lagoon. In a N−S direction, the Esfandiar Platform can
be traced for about 170 km, in an E-W direction, the platform extended for at least 35–40 km. The width of the eastern slope
of the platform is estimated at 10–15 km, the width of the western shelf lagoon varied considerably (>20–80 km). During the
Late Callovian to Middle Oxfordian, the Esfandiar Platform flourished under arid climatic conditions and supplied the slope
and basinal areas with large amounts of carbonates (suspended peri-platform muds and gravitational sediments). Export pulses
of platform material, e.g. ooids and aggregate grains, into the slope and basinal system are interpreted as highstand shedding
related to relative sealevel variations. The high-productivity phase was terminated in the Late Oxfordian when the eastern
platform areas drowned and homogeneous deep water marls of the Upper Oxfordian to Kimmeridgian Korond Formation onlapped both
the Qal'eh Dokhtar Limestone Formation and the drowned Esfandiar Limestone Formation. Tectonic instability, probably caused
by faulting at the margins of the Tabas Block in connection with rotational movements of the east-central Iranian block assemblage,
was responsible for the partial drowning of the eastern platform areas. In some areas, relicts of the platform persisted to
produce shallow-water sediments into the Kimmeridgian. 相似文献
14.
J. Alfred Fagerstrom Margaret A. Bradshaw 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2002,35(1):35-50
Study of 35 systematically collected and 10 semi‐random samples (about 100 cm 2 each) from one outcrop of the Lankey Limestone (Emsian) near Reefton, New Zealand indicates that it is a reef framestone built by tabulate (4? spp.) and clonal rugose (one sp.) corals, two species of stromatoporoids, a few bryozoans (2? spp.) and crinoids. The guild structure of the reef community and data on skeleton orientation and growth direction further indicate that there was relatively minor biostratonomic alteration of the original community. Skeletons are either in growth position or tipped, toppled or even overturned, but they have remained in situ. Other clone‐rich Lankey Limestone outcrops in the Reefton area support the notion of an upper shelf reef system and stratigraphic and sedimentologic data suggest that it was located near the Gondwana margin at a paleolatitude of about 35°S. 相似文献
15.
Prof. Dr. Baba Senowbari-Daryan 《Facies》1997,36(1):57-67
Summary
Barbafera carnica
Senowbari-Daryan (1980), a Carnian reef fossil of uncertain systematic position, is redescribed based on extraordinarily preserved material
from Carnian reef boulders of the Cassian Formation of the Southern Alps (Dolomites/Italy).Barbafera is interpreted as a worm tube characterized by a complicated wall structure.Barbafera may belong to the family SerpulidaeRafinesque. 相似文献
16.
Middle Ordovician reefs of Norway 总被引:1,自引:0,他引:1
TOM L. HARLAND 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1981,14(3):169-188
The Middle Ordovician reefs of Norway were the first to develop in the western part of the Balto-scandian epicontinental sea and are the earliest coral-stromatoporoid reefs so far reported in Europe. Small patch reefs in the Steinvika Limestone, Langesund-Skien district, consist mainly of algae, echinoderms, corals and stromatoporoids. Bryozoans, molluscs, arthropods and brachiopods are also present. The reefs developed on pelmatozoan-rich substrates and are organically zoned, consisting of a pioneer community of stemmed echinoderms and sheet algae, a high-diversity intermediate community dominated by fasciculate corals and a low diversity climax community of massive corals and stromatoporoids. These communities are interpreted as the seral stages of an autogenic ecological succession. Small patch reefs are also present in the laterally equivalent Mjøsa Limestone, Toten and Nes-Hamar districts. These are organically very similar to those in the Steinvika Limestone and developed in an identical way. A large complex, consisting of several reefs, is also present in the Mjøsa Limestone. Unlike the reefs elsewhere, which developed within shallow inshore areas, this complex developed at the outer edge of the inshore shelf. The outstanding feature of the complex is the main reef forming the offshore limit which is totally dominated by stromatoporoids and lacks a sequential development. This is due to the influence of the harsher environment at the shelf edge. 相似文献
17.
Tsutomu Nakazawa 《Facies》2001,44(1):183-210
Summary The Carboniferous-Permian (Visean-Midian) Omi Limestone in the Akiyoshi Terrane, central Japan is a large carbonate unit developed
on a seamount in the Panthalassa Ocean. As the seamount subsided during Carboniferous and Permian time, the carbonate deposition
at the top of a seamount was almost continous. Terrigenous siliciclastic sediments are absent, because the seamount was situated
in an open-ocean setting. The lower part of this seamount-type limestone records a nearly continuous Carboniferous reef succession.
Sedimentary facies in the Carboniferous part of the Omi Limestone are generally highly diverse, but their diversity varies
in each age. The Upper Carboniferous part consists of highly diversified facies including fore reef, reef front, reef crest,
sand shoal, and lagoon facies, while a simple facies assemblage, composed only of fore reef, reef front, and sand shoal facies,
occurs in the Lower Carboniferous.
The Carboniferous reef succession consists of four phases characterized, in ascending order, by the coralbryozoan-crinoid
community, problematic skeletal organism-microencruster community, chaetetid-microencruster community, and calcareous algal
community. The first phase, comprising the coral-bryozoan-crinoid community, occurs in theEndothyra spp. Zone to theEostaffella kanmerai Zone (Visean to Serpukhovian). This community acted only as sediment-bafflers and/or contributors. The second phase, represented
by the problematic skeletal organism-microencruster community, is developed in theMillerella sp. Zone to theAkiyoshiella ozawai Zone (Bashkirian to lowermost Moscovian), and the third phase, comprising the chaetetid-microencruster community, occurs
in the overlyingFusulinella biconica Zone (Lower Moscovian). These two communities are characterized by highly diversified reef-building organisms that had the
ability to build rigid frameworks. Calcareous algae and incertae sedis such asHikorocodium, solenoporaceans and phylloid algae characterize the fourth phase, which occurs in theBeedeina sp. Zone (Upper Moscovian). The changes of the reef communities were sucessive for a long period of more than 40 m.y., and
each community was distributed in various environments. In addition, the continuous subsidence of the isolated seamount resulted
in environmental stability. These properties indicate that this succession represents the biotic evolution of reef-building
organisms.
The problematic skeletal organism-microencruster community and chaetetid-microencruster community of the Late Carboniferous
formed wave-resistant and rigid frameworks along with abundant submarine cements. The growth of these reef frameworks resulted
in the formation of highly diversified sedimentary facies comparable to those of a modern reef complex. Such reefs are also
recognized in the seamount-type Akiyoshi Limestone, but rare on Carboniferous Pangean shelves. Therefore, the formation of
these types of reefs appear to be characteristic of open-ocean seamount settings, which differed from epicontinental shelf
settings in having no siliciclastic input, being exposed to relatively strong openocean waves and swells, and probably more
environmental stability resulting from the relatively continuous subsidence of the seamount. 相似文献
18.
Summary In the Kale (Gümüshane) area in the North Eastern Turkey, platform carbonates of the Berdiga Limestone were deposited during
Late Jurassic-Early Cretaceous time in environments varying from intertidal to fore reef. The sequence shows extensive lateral
and vertical alterations and interfingering of different facies types. In the upper part of the Berdiga Limestone in the Kircaova
area a bituminous thin-bedded to platy limestone and shale 5 to 6 m thick occurs at the Early/Late Aptian boundary. It is
underlain by limestones rich in silica nodules of up to 10 cm size.
A facies analysis of a section about 70 m thick including the bituminous interval was carried out in 1994/95 at the SW border
of the Kircaova area close to the road from L?rikas to Kale. The limestones consist mainly of packstones and grainstones locally
rich in calcareaous algae and forminifera. Fragments of molluscs and echinoids as well as some ostracods and calcispheres
occur. Some sponges, corals, and beds rich in molluscs occur in minor amounts in the middle part of the section which is characterized
by intertidal to shallow subtidal facies.
Algae and foraminifera indicate a Barremian-Early Aptian age of the lower part and Late Aptian age of the upper part of the
section (e.g.Salpingoporellamuehlbergii, Salpingoporella aff.melitae, Clypeina solkani, Novalesia producta), divided by the bituminous limestones.
In West Slovenia (close to the Italian border) a complete Cretaceous section occurs at Sabotin mountain containing Aptian
beds with comparable faunal composition. In contrast to the Berdiga Limestone, in Slovenia at the rim of the dinaric platform
a patch reef about 50 m in thickness is developed which is also covered by a bituminous limestones (black shale) marking the
Early/Late Aptian boundary. Faunal elements in Slovenia arePalorbitolina lenticularis, Cuneolina laurentii, Orbitolina (Mesorbitolina) texana andSalpingopoprella dinarica.
The bituminous limestone appears to be a marker horizon. At both locations it is locally rich in characeans probably indicating
a regressive maximum before another transgression began in the Late Aptian/Albian as world-wide drowning event. Possibly the
occurrence of the bituminous limestone (black shale) is associated with volcanic activity during the Aptian. If so it could
be used as a chronostratigraphic marker horizon in both areas analyzed. 相似文献
19.
《Annales de Paléontologie》2021,107(3):102508
The study of the coral biodiversity of the Upper Oligocene sedimentary series (Lower Coralline Limestone, Chattian) of Malta permitted the identification of 25 scleractinian genera represented by 41 species. Three new species are proposed: Miophora naxxarensis n. sp., Nerthastraea maltensis n. sp. and Gyrosmilia maltensis n. sp. Observations made in various Oligocene sites in Malta, especially around Naxxar and Tal Bajjada, allow to establish a suite of coral associations which may vary spatially and vertically. The identified scleractinian associations can be represented by different types of coral assemblages and bioconstructions: isolated colonies, coral beds of varying density but of large spatial extent, more cohesive coral banks (coral carpets) or patch reefs forming morphologies with gentle lateral slopes. The colonial morphologies are closely linked to these different types of bioconstructions. These coral constructions have been established and developed in shallow marine areas. The coral biodiversity of the Oligocene of Malta fits well in the evolution of the Cenozoic reef phenomenon whose development reached its peak in the Oligocene with great coral richness in the Chattian in the Mediterranean area. 相似文献
20.
Despite prejudices that comparisons of paleoecological patterns in modern and fossil reef communities are of doubtful validity, we compare the biologic response of living coralgal reefs in French Polynesia to environmental stress with an exceptionally well exposed Middle Permian sponge reef and Shamovella-microbial reef of the Capitan Limestone in New Mexico. In the western Tuamotu Archipelago, reef margins are characterized by depth-related changes of biodiversity. The subtidal basic reefbuilding community contains the highest diversity (23 coral and 6 calcareous algal species). With decreasing water depth and increasing environmental stress, diversity reaches a minimum of five taxa on the reef flat. The Capitan consists of two reef stages. Reefbuilders of the lowermost exposed part of Stage 1 formed a cement-rich sponge reef with 42 taxa (28 sponge species). Decreasing water depth along the reef face is accompanied by loss of five taxa, variations in the gross morphology of sponges and changes in framework architecture. Stage 2, dominated by Shamovella obscura, one bryozoan species and microbes, is sandwiched between two unconformities suggesting much shallower water and higher environmental stress. Despite differences in shelf profile and taxonomy, both the modern and Permian reefbuilders respond to increasing environmental stress with diversity impoverishment and dominance of binders. 相似文献