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Comparison of modern submarine fans and ancient turbidite sequences is still in its infancy, mainly because of the incompatibility
of study approaches. Research on modern fan systems mainly deals with morphologic aspects and surficial sediments, while observations
on ancient turbidite formations are mostly directed to vertical sequences. The lack of a common data set also results from
different scales of observation.
To review the current status of modern and ancient turbidite research, an international group of specialists formed COMFAN
(Committee on Fans) and met in September 1982 at the Gulf Research and Development Company research facilities in Pennsylvania.
Margin setting represents fan and/or source area 相似文献
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John M. Ferry Laurence J. Mutti Gregory J. Zuccala 《Contributions to Mineralogy and Petrology》1987,95(2):166-181
Alkali olivine basalts from Skye were simultaneously contact metamorphosed by Tertiary gabbro and granite intrusions and altered by the hydrothermal convection system that the plutons induced. Four metamorphic zones were mapped around the plutons. Furthest from the intrusions, in the primary olivine zone, metabasalts are composed of combinations of igneous olivine, augite, plagioclase, titaniferous magnetite, ilmenite, zeolites, gyrolite, sulfides, and chlorite-smectite intergrowths. Closer to the plutons, in the smectite zone, saponite and carbonate appear, primary olivine and gyrolite disappear, and zeolites decrease dramatically in abundance. Still closer to the plutons, in the amphibole zone, actinolite, edenite, chlorite, sphene, epidote, andradite, and quartz appear and saponite and chlorite-smectite intergrowths disappear. Along parts of the contact between gabbro and basalt, in the orthopyroxeneolivine zone, orthopyroxene, metamorphic olivine, and biotite appear and amphibole, chlorite, sphene, epidote, andradite, carbonate, and quartz disappear. Whole-rock chemical data indicate only minor change in the major-element chemical composition of the metabasalts during progressive metamorphism/hydrothermal alteration. Two-pyroxene eothermometry and various mineral-fluid equilibria suggest the range of peak temperatures attained in the metamorphic zones: orthopyroxene-olivine zone, 900°1, 030° C; amphibole zone, 400°–900° C; smectite and primary olivine zones, < 400° C. Mineralogical and oxygen isotopic alteration of the metabasalts were closely coupled: Basalts from the primary olivine zone with nearly unaltered igneous mineralogies have normal or near-normal wholerock
18O>+5 (SMOW); mineralogically more altered basalts from the smectite zone have whole-rock
18O=+2 to +5; still more mineralogically altered basalts from the amphibole zone (with one exception) have
18O<+ 2; completely recrystallized hornfelses from the orthopyroxene-olivine zone have
18O<0. The principal mechanism of isotope exchange between basalt and metamorphic/ hydrothermal fluid probably was heterogeneous mineralfluid reaction.Metabasalts from the orthopyroxene-olivine zone are mineralogically fresh pyroxene hornfelses that record crystallization temperatures > 1,000° C yet have highly altered whole-rock oxygen isotope compositions,
18O<0%. The hornfelses chemically interacted with metamorphic/hydrothermal fluids either at very high temperatures or while they were heated to > 1,000° C or both. Their mineralogy, however, rules out significant water-rock interaction after they cooled below 900° C. Hydrothermal convection on Skye was a two-stage process: (a) fluid flow through wall rocks initially was pervasive while they are heated; (b) fluid flow after the thermal peak in the wall rocks was sufficiently channelized that rocks such as those in the orthopyroxeneolivine zone were isolated from further fluid-rock interaction during all or almost all of the cooling history of the hydrothermal system. 相似文献
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Relatively few studies have so far addressed diagenetic processes in Heterozoan carbonates and the role that sediment composition and depositional facies exert over diagenetic pathways. This paper presents a study of Oligocene shallow-water, Heterozoan carbonates from the Maltese Islands. We investigate stratigraphic distribution, abundance and timing of diagenetic features and their relationship to sediment composition and depositional facies. The studied carbonate rocks comprise rud- to packstones of the Heterozoan association predominantly containing coralline red algae, bryozoans, echinoids and benthic foraminifers. XRD analyses show that all high-Mg calcite has been transformed to low-Mg calcite and that no aragonite is preserved. Diagenetic processes include dissolution of aragonitic biota, neomorphism of high-Mg calcitic biota to low-Mg calcite and cementation by fibrous, bladed, epitaxial and blocky cements. Stable isotopes on bulk rock integrated with petrographic data suggest that the study interval was not exposed to significant meteoric diagenesis. We interpret early cementation to have taken place in the marine and marine burial environment. The distribution and abundance of early diagenetic features, determining the diagenetic pathway, can be related to the primary sediment composition and depositional texture. Sorting and micrite content are important controls over the abundance of diagenetic features. 相似文献
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Emiliano Mutti 《Geo-Marine Letters》1984,3(2-4):199-202
The Eocene Hecho Group submarine-fan and basin-plain turbidites fill an elongate basin in the south-central Pyrenees that
was tectonically active during deposition. The total volume of these sediments is about 21,000 to 26,000 km3. The bulk of the sand by-passed the fan-channel zone and was deposited in the lobe and fan-fringe environments. The stratigraphically
lower part of the Hecho submarine fan was deposited during relative lowering of sea level.
Margin setting represents fan and/or source area 相似文献
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The Cengio sandstone member of the Tertiary Piedmont Basin in northwestern Italy has a conservatively estimated volume of
2.5 to 3 km3 (length: 6.4 km; width: 4.8 km; thickness: 170 m). It is interpreted as a sandstone-rich submarine fan deposit. The Cengio
member consists of eight tabular depositional sandstone lobes that are 5- to 25-m thick. These lobes filled a submarine structural
depression and onlap and/or pinch-out against bounding slope mudstones. The stacking of the lobe units was related to synsedimentary
tectonism.
Margin setting represents fan and/or source area 相似文献
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Carbonate systems along nutrient and temperature gradients: some sedimentological and geochemical constraints 总被引：3，自引：0，他引：3
Research over the past several decades has clearly demonstrated that changes in the ocean environment have had major impacts on carbonate systems. Changes in climate, ocean circulation and seafloor spreading rates have influenced temperature and seawater chemistry, including carbonate saturation state and nutrient availability, and thereby have determined boundary conditions for the biota that form carbonate platforms. In turn, the biota determine accumulation rates and facies zonations, thus controlling platform geometry and facies dynamics. In the first section of this paper, we examine how nutrient availability influences carbonate facies associations. We first discuss the role of temperature and nutrient gradients in the modern ocean and their influence on biotic associations. Then we discuss how carbonate sedimentation can be characterized along nutrient gradients. In the second section, we review proxies currently used to reconstruct paleoproductivity in open ocean environments and discuss their applicability to neritic carbonate systems. We highlight the variety of existing proxies and their limitations, and suggest that multiple lines of evidence are needed for valid interpretations. Our short review discusses sedimentological, biogenic, and geochemical proxies that can be used to reconstruct past nutrient fluxes and to constrain paleoceanographic controls over the distribution of carbonate associations. However, it also reveals that more data and case studies are needed that integrate shallow and deep water carbonate sequences and elucidate the links between temperature vs. nutrient supplies changes and facies in ancient carbonate sequences.
相似文献
| Maria MuttiEmail: |
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Carbonate platform drownings are frequent, often synchronous global occurrences, yet explanations for these world-wide events remain unsatisfactory. In the Central Apennines, Lower and Middle Miocene carbonate rocks deposited on a 'temperate' ramp in the Maiella platform margin record two episodes of platform drowning followed by hemipelagic sedimentation, dated as latest Oligocene–Aquitanian (26–23 M a) and as Burdigalian–Langhian (20–16 Ma). A high-resolution stratigraphy, based on strontium- isotopes, allows us to correlate key phases of platform evolution with events recorded in deep water ocean sediments. This paper suggests that high weathering rates and nutrient input in the Mediterranean during the early and middle Miocene –possibly linked to the uplift of the Tibetan region – set the preconditions for platform drowning, which were ultimately caused by rapid eustatic sea-level rises. 相似文献