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1.
I. M. SÁNCHEZ-ALMAZO† J. C. BRAGA† J. DINARÈS-TURELL‡ J. M. MARTÍN B. SPIRO§ 《Sedimentology》2007,54(3):637-660
The Cariatiz section lies at the toe of the palaeoslope of the Messinian Cariatiz fringing reef, at the northern margin of the Neogene Sorbas Basin in SE Spain. Distal-slope reef deposits in the upper part of the section can be traced laterally to the reef core of the last episodes of reef progradation. The underlying deposits are alternating diatomitic marl, marl and silty marl that intercalate with sandstone beds. Combined lithological changes, variations in proportions of warm-water planktic foraminifera and δ 18O values suggest that at least seven, probably precessional, cycles are recorded throughout the Cariatiz section. The correlation of seven cycles in the pelagic deposits to seven reef progradation cycles, and associated vertical shifts in reef facies, indicates relative sea-level oscillations of several tens of metres. Biostratigraphic and palaeomagnetic data suggest that both the Cariatiz section and the fringing reef formed during the reverse polarity Chron C3r. Surface-water temperatures seem to be the major factor controlling carbonate production in the reef system. Deposition of bioclastic calcirudite and calcarenite, with no active coral growth, took place at the lowest sea-level within each reef cycle during temperature minima within each precessional cycle. Porites framework and reef-slope deposits with Halimeda gravel, in contrast, formed during temperature rises and thermal maxima within precessional cycles. 相似文献
2.
Tectonic, eustatic and environmental controls on mid-Cretaceous carbonate platform deposition, south-central Pyrenees, Spain 总被引：2，自引：0，他引：2
Cenomanian–Turonian strata of the south‐central Pyrenees in northern Spain contain three prograding carbonate sequences that record interactions among tectonics, sea level, environment and sediment fabric in controlling sequence development. Sequence UK‐1 (Lower to Upper Cenomanian) contains distinct lagoonal, back‐margin, margin, slope and basin facies, and was deposited on a broad, flat shelf adjacent to a deep basin. The lack of reef‐constructing organisms resulted in a gently dipping ramp morphology for the margin and slope. Sequence UK‐2 (Upper Cenomanian) contains similar shallow‐water facies belts, but syndepositional tectonic modification of the margin resulted in a steep slope and deposition of carbonate megabreccias. Sequence UK‐3 (Lower to Middle Turonian) records a shift from benthic to pelagic deposition, as the shallow platform was drowned in response to a eustatic sea‐level rise, coupled with increased organic productivity. Sequences UK‐1 to UK‐3 are subdivided into lowstand, transgressive and highstand systems tracts based on stratal geometries and facies distribution patterns. The same lithologies (e.g. megabreccias) commonly occur in more than one systems tract, indicating that: (1) the depositional system responded to more than just sea‐level fluctuations; and (2) similar processes occurred during different times throughout sequence development. These sequences illustrate the complexity of carbonate platform dynamics that influence sequence architecture. Rift tectonics and flexural subsidence played a major role in controlling the location of the platform margin, maintaining a steep slope gradient through syndepositional faulting, enhancing slope instability and erosion, and influencing depositional processes, stratal relationships and lithofacies distribution on the slope. Sea‐level variations (eustatic and relative) strongly influenced the timing of sequence and parasequence boundary formation, controlled changes in accommodation and promoted platform drowning (in conjunction with other factors). Physico‐chemical and climatic conditions were responsible for reducing carbonate production rates and inducing platform drowning. Finally, a mud‐rich sediment fabric affected platform morphology, growth geometries (aggradation vs. progradation) and facies distribution patterns. 相似文献
3.
FABRIZIO BERRA 《Sedimentology》2007,54(4):721-735
In the Concarena‐Pizzo Camino Massif (Lombardy Basin, Southern Alps, Italy) the lateral transition from Ladinian‐Carnian carbonate platforms to coeval intraplatform basins is preserved. The succession records the sedimentological evidence of a sea‐level fall on a flat‐topped platform with a narrow marginal reef rim and its effects in the adjacent deeper‐water basin. Repeated high‐frequency exposures of the platform top are recorded by a peritidal–supratidal succession that overlies subtidal inner platform facies of the former highstand system tract (HST). On the slope and in the basin, the sea‐level fall is recorded by a few metre thick succession of bioclastic packstones. These facies directly lie on coarse clinostratified breccia bodies (slope facies of the former HST) or on resedimented, well‐bedded, dark laminated limestones (basinal facies of the HST). This facies distribution indicates that during the sea‐level fall carbonate production on the platform top decreased rapidly and that sedimentation in the basin was mainly represented by condensed facies. Microfacies record an enrichment, during low stand, in pelagic biota (packstones with radiolarians and spiculae), whereas the occurrence of platform‐derived, shallow‐water materials is limited to thin lenses of reworked and micritized Fe‐rich oolites and bioclasts (mainly pelecypods and echinoderms). The facies association in the Concarena‐Pizzo Camino Massif demonstrates that a highly‐productive carbonate factory was almost completely turned off during the emergence of the platform top at a sequence boundary, leading to low‐stand starvation in the basin. The reconstruction of the stratigraphic evolution of the Concarena‐Pizzo Camino carbonate platform therefore represents a significant case history for the study of the behaviour of ancient carbonate systems during a fall in sea‐level, independent of its origin (eustatic or tectonic). 相似文献
4.
下扬子盆地石炭纪的岩石学特征及沉积相 总被引：5，自引：0，他引：5
位于扬子板块东部的下扬子盆地，在石炭纪时，为被动大陆边缘的陆表海沉积，陆源碎屑来自于北边的胶南古陆和南边的江南古陆东延部分─—皖浙赣古陆。石炭系分为上、下两统。早石炭世，盆地南部宣城、广德等地主要发育碎屑岩，中部巢县、南京一带以及北部滨海、洪泽一带为碎屑岩和碳酸盐岩沉积。从南往北，金陵期从滨岸碎屑岩相→开阔海台地碳酸盐岩相→潮坪碳酸盐岩和碎屑岩相；高骊山期为滨岸平原沼泽碎屑岩相→浅海陆棚碎屑岩相→海岸萨布哈白云岩、石膏、碎屑岩相；和州期盆地南部隆起，中部到北部为礁及礁后泻湖一潮坪碳酸盐岩相→开阔海台地碳酸盐相。晚石炭世主要是碳酸盐沉积，黄龙期从滨岸石英砾岩相→潮坪白云岩相→开阔海台地碳酸盐岩相；船山期是黄龙期开阔海台地碳酸盐岩相的继续，以发育核形石生物碎屑颗粒岩为特征。整个盆地的岩相带均以ＮＥＥ—ＮＥ方向展布。 相似文献
5.
Well‐exposed Mesozoic sections of the Bahama‐like Adriatic Platform along the Dalmatian coast (southern Croatia) reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding Late Jurassic (Tithonian) shallow platform‐interior (over 750 m thick, ca 5–6 Myr duration). Facies within parasequences include dasyclad‐oncoid mudstone‐wackestone‐floatstone and skeletal‐peloid wackestone‐packstone (shallow lagoon), intraclast‐peloid packstone and grainstone (shoal), radial‐ooid grainstone (hypersaline shallow subtidal/intertidal shoals and ponds), lime mudstone (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Parasequences in the overall transgressive Lower Tithonian sections are 1–4·5 m thick, and dominated by subtidal facies, some of which are capped by very shallow‐water grainstone‐packstone or restricted lime mudstone; laminated tidal caps become common only towards the interior of the platform. Parasequences in the regressive Upper Tithonian are dominated by peritidal facies with distinctive basal oolite units and well‐developed laminate caps. Maximum water depths of facies within parasequences (estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences) were generally <4 m, and facies show strongly overlapping depth ranges suggesting facies mosaics. Parasequences were formed by precessional (20 kyr) orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles. Parasequences are arranged in third‐order sequences that lack significant bounding disconformities, and are evident on accommodation (Fischer) plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position. Modelling suggests that precessional sea‐level changes were small (several metres) as were eccentricity sea‐level changes (or precessional sea‐level changes modulated by eccentricity), supporting a global, hot greenhouse climate for the Late Jurassic (Tithonian) within the overall ‘cool’ mode of the Middle Jurassic to Early Cretaceous. 相似文献
6.
利用钻井和二维地震资料, 对曾母盆地南康台地以及L构造中新统碳酸盐建造的三级层序发育特征进行解剖, 归纳总结研究区碳酸盐岩层序发育模式, 认为曾母盆地在中中新世-晚中新世(5.3~16 Ma)期间发育3期较大规模的碳酸盐岩沉积旋回, 在地层上可将其划分为3个三级层序, 即SQ1、SQ2和SQ3层序.其中SQ1与SQ3应该属于经典Ⅰ型碳酸盐岩层序, 在其岩性上由低位域的致密藻灰岩沉积、水进域的泥质灰岩和高位域的珊瑚灰岩组合构成, 代表了从开阔海沉积环境过渡至礁滩相沉积环境的发育过程;而SQ2应属于淹没不整合型碳酸盐岩层序, 以泥质灰岩凝缩层+高位域的珊瑚灰岩或碎屑灰岩序列组合为特征, 其发育基本处于水体环境持续变浅的沉积环境中. 相似文献
7.
《Sedimentary Geology》2001,139(3-4):319-340
Facies analysis of the upper Kimmeridgian rocks in the outcrops located near Ricla (Zaragoza province, northeast Spain) and the integration of the resultant data in a broader context (the northern part of the Iberian Basin), has produced two general models showing the facies distribution and the processes that controlled the sedimentation in the Kimmeridgian carbonate ramp. Using these two models the transition from shallow to relatively deep environments of the carbonate ramp is examined in detail. Model 1 corresponds to the development of a mixed carbonate-siliciclastic ramp during a slow rise and stillstand of sea level (Sequence 1-HST), whereas Model 2 represents the growth of a pure carbonate ramp during a rapid rise of sea level (Sequence 2-TST).Carbonate production was higher in the shallow ramp domains (coral reefs and oolitic shoals in Model 1 and reefs in Model 2) than in deeper domains, where there is no indication of significant pelagic or benthic production. The activity of unidirectional return flows induced by winter storms and hurricanes, played an important role in the redistribution of the sediment across the ramp, generating different coarse-grained deposits. In the inner and mid-ramp settings dunes, lower scale bedforms and tempestites occur in Model 1, and storm lobes, bars and tempestites in Model 2. Moreover, a significant bulk of the carbonate mud produced in shallow areas would eventually be resedimented in the outer ramp as suspended load in the density currents. Stillstand of sea level in Model 1 involved a rapid progradation of the inner and proximal mid-ramp carbonate and siliciclastic facies. The rapid relative sea level rise of Model 2 is determined by the dominance of the carbonate facies and by the presence of aggradational geometries in the transitional area between shallow and deep-ramp domains. The presence of relatively thick sections in the outer-ramp settings (instead of condensed sections, as observed in Model 1) during times of sea level rise (Model 2) can mainly be explained by the increase of the shallow production in the reef dominated areas. 相似文献
8.
Mohammad Ali Kavoosi 《Geological Journal》2016,51(4):523-544
Upper Callovian to Tithonian (late Jurassic) sediments represent an important hydrocarbon reservoir in the Kopet‐Dagh Basin, NE Iran. These deposits consist mainly of limestone, dolostone, and calcareous mudstone with subordinate siliciclastic interbeds. Detailed field surveys, lithofacies and facies analyses at three outcrop sections were used to investigate the depositional environments and sequence stratigraphy of the Middle to Upper Jurassic interval in the central and western areas of the basin. Vertical and lateral facies changes, sedimentary fabrics and structures, and geometry of carbonate bodies resulted in recognition of various carbonate facies related to tidal flats, back‐barrier lagoon, shelf‐margin/shelf‐margin reef, slope and deep‐marine facies belts. These facies were accompanied by interbedded beach and deep marine siliciclastic petrofacies. Field surveys, facies analysis, parasequences stacking patterns, discontinuity surfaces, and geometries coupled with relative depth variation, led to the recognition of six third‐order depositional sequences. The depositional history of the study areas can be divided into two main phases. These indicate platform evolution from a rimmed‐shelf to a carbonate ramp during the late Callovian–Oxfordian and Kimmeridgian–Tithonian intervals, respectively. Significant lateral and vertical facies and thickness changes, and results obtained from regional correlation of the depositional sequences, can be attributed to the combined effect of antecedent topography and differential subsidence related to local tectonics. Moreover, sea‐level changes must be regarded as a major factor during the late Callovian–Tithonian interval. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
9.
《Sedimentology》2018,65(4):1097-1131
Wide carbonate platform environments developed on the western passive margin of the Tethys during the Late Triassic, after a major climate change (Carnian Pluvial Episode) that produced a crisis of high‐relief microbial carbonate platforms. The peritidal succession of this epicontinental platform (Dolomia Principale/Hauptdolomit, Dachstein Limestone) is widespread in the Mediterranean region. However, the start‐up stage is not fully understood. The original platform to basin depositional geometries of the system have been studied in the north‐eastern Southern Alps, close to the Italian/Slovenian boundary where they are exceptionally preserved. Sedimentological features have been investigated in detail by measuring several stratigraphic sections cropping out along an ideal depositional profile. The analysis of the facies architecture allowed reconstruction of the palaeoenvironments of the Dolomia Principale platform during its start‐up and early growth stages in the late Carnian. The carbonate platform was characterized by an outer platform area, connected northward to steep slopes facing a relatively deep basin. Southward, the outer platform was connected to inner sheltered environments by a narrow, often emerged shelf crest. Behind this zone, carbonate sedimentation occurred in shallow lagoons and tidal flats, passing inward to a siliciclastic mudflat. The Dolomia Principale platform was initially aggrading and able to keep pace with a concomitant sea‐level rise, and then prograding during the late Carnian. This stratigraphic interval was correlated with the Tuvalian succession of the Dolomites, allowing depiction of the depositional system on a wide scale of hundreds of kilometres. This large‐scale depositional system presents features in common with some Palaeozoic and Mesozoic carbonate build‐ups (for example, the Permian Capitan Reef complex, Anisian Latemar platform), both in terms of architecture and prevailing carbonate producers. A microbial‐dominated carbonate factory is found in the outer platform and upper slope. The recovery of high‐relief microbial carbonate platforms marks the end of the Carnian Pluvial Episode in the Tuvalian of Tethys. 相似文献
10.
Ground‐penetrating radar has not been applied widely to the recognition of ancient carbonate platform geometries. This article reports the results of an integrated study performed on an Upper Jurassic outcrop from the south‐east Paris basin, where coral bioherms laterally change into prograding depositional sequences. Ground‐penetrating radar profiles illustrate the different bedding planes and major erosional unconformities visible at outcrop. A ground‐penetrating radar profile conducted at the base of the cliff displays a palaeotopographic surface on which the outcropping bioherms settled. The excellent penetration depths of the ground‐penetrating radar (20 m with a monostatic 200 MHz antenna) images the carbonate platform geometries, ranging between outcrop workscale (a few metres) and seismic scale (several hundreds of metres). This study supports recent evidence of icehouse conditions and induced sea‐level fluctuations controlling the Upper Jurassic carbonate production. 相似文献
11.
海南岛排浦礁区由珊瑚岸礁和堤礁及其间水域组成。因堤礁的障壁作用和丰富的陆源物质供应,研究区内形成清水和浑水两类沉积环境,产出清水碳酸盐和浑水碳酸盐两列沉积体系,并形成礁源沉积、陆源沉积和混合沉积三类沉积物。文中详细论述了各类沉积的特征,讨论了沉积体系的演化过程:全新世早期是单一的陆源碎屑沉积体系,全新世中期海侵,气温转暖,形成早期排浦岸礁与大铲堤礁的雏型,全新世晚期堤礁进入成熟阶段,其障壁作用加强,最终形成清水与浑水两种沉积环境和两列沉积体系。 相似文献
12.
贵州紫云扁平村石炭纪珊瑚礁剖面微相分析与沉积相 总被引：10，自引：3，他引：7
扁平村生物礁产于马平组Triticites带内,Fomitchevella骨架构成生物礁主体。扁平村的这种以珊瑚为主要造礁生物的石炭纪生物礁在全球也是不多见的。本文以实测剖面微相分析为主要手段,观察、分析珊瑚礁的生长、沉积环境,对该珊瑚礁的剖面进行详细的微相分析。我们总结了6个微相;划分出5个沉积相:在剖面上由下至上,相1较浅的受保护的台地相,相2搅动水中的浅滩相,相3较深的开阔台地相,相4浪基面以上斜坡相,珊瑚礁在这个相上发育起来,就是相5珊瑚礁相,再向上为相3,相1;进一步总结出了与圆丘礁缓坡类型相似的局部相模式;并分析了珊瑚礁生长、沉积环境。总体上剖面沉积环境为潮下开阔台地环境。 相似文献
13.
F. J. Rodríguez-Tovar I. Sánchez-Almazo E. Pardo-Igúzquiza J. C. Braga J. M. Martín 《International Journal of Earth Sciences》2013,102(6):1735-1755
Spectral analysis of the Messinian Abad marls in the Cariatiz section (Sorbas Basin, south-eastern Spain) reveals three relevant orders of cyclicity. The most significant cycle is in the lowest frequency (average thickness of 365 cm, 4–5 cycles in the section). It is recorded in the composition of planktic foraminiferal assemblages indicative of surface-water temperature, planktic and benthic stable isotope signals, and carbonate proportions. The planktic assemblages, isotope values and carbonate proportions also record a middle-frequency cycle with an average of 177 cm (9–10 cycles in the section). The highest frequency cycle (average of 132 cm, 12–13 cycles in the section) is mainly reflected in siliciclastic and calcite proportions. Age constraints and cycle patterns suggest that the lowest frequency cycle was forced by orbital obliquity, whereas the two higher-frequency ones are related to precession. Obliquity seems to have controlled major changes in surface-water temperature in the Sorbas Basin during the early Messinian. Surface-water temperature was also affected by precession, with changes in weathering and run-off. Spectral analysis has also been applied to vertical shifts of reef facies throughout the progradation of the Cariatiz reef. This reef is coeval with the Cariatiz section. Vertical shifts of reef talus breccias point to the existence of 4–5 major cycles of sea-level change, whereas 7–9 higher-frequency cycles are reflected in the repeated occurrence of lowstand, non-reefal deposits. Correlation with the cycles observed at the Cariatiz section suggests that obliquity forced glacio-eustatic sea-level oscillations in the western Mediterranean during the Late Miocene. 相似文献
14.
15.
Influence of sedimentary setting on the use of magnetic susceptibility: examples from the Devonian of Belgium 总被引：1，自引：0，他引：1
Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea‐level variations. This paper explores the link between magnetic susceptibility, depositional setting and environmental parameters. These environmental parameters include distal–proximal transects, microfacies successions and fourth‐order trends on different carbonate platform types (platform, ramp, carbonate mound or atoll) during different Devonian stages (Eifelian, Givetian and Frasnian). Average magnetic susceptibility values over a distal–proximal‐trending facies succession vary markedly with depositional setting. On carbonate platforms, average magnetic susceptibility generally increases towards the top of shallowing‐upward sequences. On a distal–proximal transect, average magnetic susceptibility is intermediate for the deepest facies, decreases for the reef belts and increases to a maximum in the back‐reef zone. In ramps and atolls, magnetic susceptibility trends clearly differ; average magnetic susceptibility generally decreases towards the top of shallowing‐upward sequences and is highest in the deepest facies. The strong relationship between magnetic susceptibility, facies and sequences implies a strong environmental influence. However, the different responses in the different platform types suggest that sea‐level changes leading to variation in detrital input is not the only parameter controlling average magnetic susceptibility values. Other primary or secondary processes also probably influenced magnetic mineral distribution. Primary processes such as carbonate production and water agitation during deposition are probably key factors. When carbonate production is high, the proportion of magnetic minerals is diluted and the magnetic susceptibility signal decreases. High water agitation during deposition will also selectively remove magnetic minerals and will lead to low average magnetic susceptibility values. These parameters explain the lowest values observed on the reef platform, inner ramp and atoll crown, which are all in areas characterized by higher carbonate production and greater water agitation during deposition. The lowest values observed in the lagoon inside the atoll crown can be related to detrital isolation by the atoll crown. However, other parameters such as biogenic magnetite production or diagenesis can also influence the magnetic signal. Diagenesis can change magnetism by creating or destroying magnetic minerals. However, the influence of diagenesis probably is linked strongly to the primary facies (permeability, amount of clay or organic matter) and probably enhanced the primary signal. The complexity of the signal gives rise to correlation problems between different depositional settings. Thus, while magnetic susceptibility has the potential to be an important correlation tool, the results of this investigation indicate that it cannot be used without consideration of sedimentary processes and depositional environments and without strong biostratigraphical control. 相似文献
16.
Ricardo M. Palma Diego A. Kietzmann Susana Adamonis Jos Lpez Gmez 《Sedimentary Geology》2009,221(1-4):127-140
The Neuquén back-arc basin is located on the west margin of the South American platform between latitudes 36° and 40° S. The basin is famous for its continuous sedimentary record from the Late Triassic to Cenozoic comprising continental and marine clastic, carbonate, and evaporitic deposits up to 2.600 m in thickness.The stratigraphical and paleontological studies of the outcrops of the La Manga Formation, Argentina, located near the Bardas Blancas region, Mendoza province (35° S and 69° O) allow the reconstruction of the sedimentary environments of an Oxfordian carbonate ramp, where outer ramp, middle ramp, inner ramp (oolitic shoal), inner ramp margin (patch reef) lagoon and paleokarst were differentiated. The reefs consist of back reef facies and in situ framework of coral boundstones that was formed at the top of shallowing-upward succession.Coral reefs were analyzed by defining coral colonies shapes, paleontological content, coral diversity and taphonomy studies. In some studied sections abundant fragments of gryphaeids, encrusting bryozoans, and isolated sponges provided a suitable substrate for coral colonization; however, other sections show an increase in the proportions of ooids, peloidal and coral intraclasts.The core reef facies is composed of white-grey unstratified and low diversity scleractinian coral limestone dominated by robust and thinly branching corals with cerioid–phocoid growths and massive coral colonies with meandroid–thamnasteroid growth forms.The assemblage is characterized by Actinastraea sp., Australoseris sp., Thamnasteria sp. and Garateastrea sp. Internal facies organization and different types of coral colonies allow to recognize the development of varying framework as well as intercolony areas. A superstratal growth fabric characterizes the coral assemblage. On the basis of coral growth fabric (branche and domal types), the reef of La Manga Formation is considered a typical mixstones. The intercolony areas consist of biomicrites and biomicrorudites containing abundant coral fragments, parautochthonous gryphaeids and another bivalves (Ctenostreon sp.), gastropods (Harpagodes sp., Natica sp.), echinoderms test and spines (Plegiocidaris sp.), miliolids, Cayeuxia sp., Acicularia sp., Salpingoporella sp., intraclasts, ooids, peloids and coated grains.The domal growth forms are probably more protected against biological and physical destruction, meanwhile delicate branching growth forms with very open and fragile framework were more affected and fragmented due to wave action and bioerosion.The reef fabric shows different intervals of truncation as consequence of erosion resulting from coral destruction by storm waves or currents. The maximum flooding surface separates oolitic shoal facies below from the aggradational and progradational coralline limestones facies above. Subsequent sea-level fall and karstification (148 Ma) affected reef and oolitic facies. 相似文献
17.
生物礁及碳酸盐台地是南海南部重要的油气储层之一,但目前对万安盆地生物礁的识别及碳酸盐台地沉积相带的划分尚不够深入.基于钻井和地震数据对该区的生物礁及碳酸盐台地进行了精细刻画,万安盆地中生物礁及碳酸盐台地的发育可分为4个演化阶段:早中新世时期,碳酸盐台地初始发育,台地规模小、数量少,零星分布于盆地中部;中中新世台地发育进入繁盛阶段,主要分布于北部隆起、中部隆起及隆起周缘的斜坡之上,横向上呈东、西带状展布,此时期的生物礁以台地边缘礁和块状礁为主;至晚中新世时期,碳酸盐台地开始衰退,而生物礁类型全、数量多,包括台地边缘礁、块状礁、塔礁、点礁等;上新世以来,生物礁及碳酸盐台地全面被淹没,盆地内部不再有生物礁及碳酸盐台地的发育.构造作用和相对海平面变化控制了碳酸盐台地的发育演化过程,古近纪基底断裂产生的地形控制了生物礁及碳酸盐台地初始发育位置及后期发育的空间分布,晚中新世以来的快速沉降和相对海平面变化控制了台地的衰退及淹没过程. 相似文献
18.
Jürgen Titschack Daniel Baum Ricardo De Pol‐Holz Matthias López Correa Nina Forster Sascha Flögel Dierk Hebbeln André Freiwald 《Sedimentology》2015,62(7):1873-1898
Cold‐water coral ecosystems present common carbonate factories along the Atlantic continental margins, where they can form large reef structures. There is increasing knowledge on their ecology, molecular genetics, environmental controls and threats available. However, information on their carbo‐nate production and accumulation is still very limited, even though this information is essential for their evaluation as carbonate sinks. The aim of this study is to provide high‐resolution reef aggradation and carbonate accumulation rates for Norwegian cold‐water coral reefs from various settings (sunds, inner shelf and shelf margin). Furthermore, it introduces a new approach for the evaluation of the cold‐water coral preservation within cold‐water coral deposits by computed tomography analysis. This approach allows the differentiation of various kinds of cold‐water coral deposits by their macrofossil clast size and orientation signature. The obtained results suggest that preservation of cold‐water coral frameworks in living position is favoured by high reef aggradation rates, while preservation of coral rubble prevails by moderate aggradation rates. A high degree of macrofossil fragmentation indicates condensed intervals or unconformities. The observed aggradation rates with up to 1500 cm kyr?1 exhibit the highest rates from cold‐water coral reefs so far. Reef aggradation within the studied cores was restricted to the Early and Late Holocene. Available datings of Norwegian cold‐water corals support this age pattern for other fjords while, on the shelf, cold‐water coral ages are reported additionally from the early Middle Holocene. The obtained mean carbonate accumulation rates of up to 103 g cm?2 kyr?1 exceed previous estimates of cold‐water coral reefs by a factor of two to three and by almost one order of magnitude to adjacent sedimentary environments (shelf, slope and deep sea). Only fjord basins locally exhibit carbonate accumulation rates in the range of the cold‐water coral reefs. Furthermore, cold‐water coral reef carbonate accumulation rates are in the range of tropical reef carbonate accumulation rates. These results clearly suggest the importance of cold‐water coral reefs as local, maybe regional to global, carbonate sinks. 相似文献
19.
A common assumption in the geological analysis of modern reefs is that coral community zonation seen on the surface should also be found in cores from the reef interior. Such assumptions not only underestimate the impact of tropical storms on reef facies development, but have been difficult to test because of restrictions imposed by narrow‐diameter cores and poor recovery. That assumption is tested here using large‐diameter cores recovered from a range of common zones across three Campeche Bank reefs. It is found that cores from the reef‐front, crest, flat and rubble‐cay zones are similar in texture and coral composition, making it impossible to recognize coral assemblages that reflect the surface zonation. Taphonomic signatures imparted by variations in encrustation, bioerosion and cementation, however, produce distinct facies and delineate a clear depth zonation. Cores from the reef‐front zone (2–10 m depth) are characterized by sections of Acropora palmata cobble gravel interspersed with sections of in‐place (but truncated) A. palmata stumps. Upper surfaces of truncated colonies are intensely bioeroded by traces of Entobia isp. and Gastrochaenolites isp. and encrusted by mm‐thick crustose corallines before colony regeneration and, therefore, indicate punctuated growth resulting from a hurricane‐induced cycle of destruction and regeneration. Cores from the reef crest/flat (0–2 m depth) are also characterized by sections of hurricane‐derived A. palmata cobble‐gravels as well as in‐place A. palmata colonies. In contrast to the reef front, however, these cobble gravels are encrusted by cm‐thick crusts of intergrown coralline algae, low‐relief Homotrema and vermetids, bored by traces of Entobia isp. and Trypanites isp. and coated by a dense, peloidal, micrite cement. Cores from the inter‐ to supratidal rubble‐cay zone (+0–5 m) are only composed of A. palmata cobble gravels and, although clasts show evidence of subtidal encrustation and bioerosion, these always represent processes that occurred before deposition on the cay. Instead, these gravels are distinguished on the basis of their limited bioerosion and marine cements, which exhibit fabrics formed in the intertidal zone. These results confirm that hurricanes have a major influence on facies development in Campeche Bank reefs. Instead of reflecting the surface coral zonation, each facies records a distinctive, depth‐related set of taphonomic processes, which reflect colonization, alteration and stabilization following the production of new substrates by hurricanes. 相似文献
20.
川西泥盆系观雾山组沉积相研究缺乏横向对比,沉积模式还存在争议。根据川西北部白家乡大木垭剖面与何家梁剖面实测成果,对中泥盆统观雾山组沉积相进行了分析,认为:大木垭剖面与何家梁剖面观雾山组为碳酸盐镶边台地沉积,期间发生短暂的碳酸盐缓坡化;桂溪剖面观雾山组同属碳酸盐台地边缘,观雾山组中段发育开阔台地深水沉积,并不是前人认为的潟湖沉积。研究区碳酸盐镶边台地包括台地边缘和前缘斜坡两种亚相,前缘斜坡亚相发育于何家梁剖面,以塌积岩沉积为标志。碳酸盐缓坡包括深水缓坡和浅水缓坡两种亚相。随着海平面变化,观雾山组碳酸盐岩发育三个沉积旋回,第一、第三沉积旋回为镶边台地沉积,第二沉积旋回为碳酸盐缓坡沉积。观雾山组沉积微相对储层的分布起控制作用:生物碎屑滩和上斜坡微相为有利储层发育相带;生物礁中在油气运移之前形成的溶蚀孔洞已被白云石和方解石充填,滩间微相泥质(泥晶)白云岩不利于溶蚀孔洞形成,这二者均不是有利储层发育相带。 相似文献