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Some technical problems commonly encountered in marine heat-flow measurements have been overcome with a digitally recording seabottom probe containing in its pressure case no moving parts except a stepper relay. The probe stores digitally at regular time intervals the resistances of 11 thermistors in a 240-word CMOS memory. After return to the surface, it is connected to a digital printer to read out the measured data. The probe can be reused immediately since it need not be opened or recharged. 相似文献
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Oligocene and Early Miocene coral assemblages from three sections of central Iran are investigated with respect to their
palaeoecological and palaeobiogeographic implications. These corals are compared with faunas from the Mediterranean Tethys
and the Indopacific. Associated larger foraminifers are used for biostratigraphy and to support the palaeoecological interpretation.
The studied sections are situated in the foreland basins of the Iranian Plate which is structured into a fore-arc and a back-arc
basin separated by a volcanic arc. The coral assemblages from Abadeh indicate a shallowing-upward trend. Infrequently distributed
solitary corals at the base of the section indicate a turbid environment. Above, a distinct horizon characterised by a Leptoseris-Stylophora assemblage associated with lepidocyclinids and planktonic foraminifers is interpreted as maximum flooding surface. Small
patch reefs with a Porites-Faviidae assemblage are a common feature of Late Oligocene to Early Miocene coral occurrences and indicate water depths of
less than 20 m. The diversity of the coral faunas shows marked differences. Oligocene corals from the Esfahan-Sirjan fore-arc
basin comprise more than 45 species of 32 genera and occur in a wide range of environments. Early Miocene corals from the
Qom back-arc basin are less frequent, show a lower diversity (13 genera with 15 species) and occur in single horizons or small
patch reefs.
Received: 4 December 1998 / Accepted: 3 June 1999 相似文献
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Elishevah van Kooten Larissa Cavalcante Daniel Wielandt Martin Bizzarro 《Meteoritics & planetary science》2020,55(3):575-590
CM meteorites are dominant members of carbonaceous chondrites (CCs), which evidently accreted in a region separated from the terrestrial planets. These chondrites are key in determining the accretion regions of solar system materials, since in Mg and Cr isotope space, they intersect between what are identified as inner and outer solar system reservoirs. In this model, the outer reservoir is represented by metal‐rich carbonaceous chondrites (MRCCs), including CR chondrites. An important question remains whether the barrier between MRCCs and CCs was a temporal or spatial one. CM chondrites and chondrules are used here to identify the nature of the barrier as well as the timescale of chondrite parent body accretion. We find based on high precision Mg and Cr isotope data of seven CM chondrites and 12 chondrules, that accretion in the CM chondrite reservoir was continuous lasting <3 Myr and showing late accretion of MRCC‐like material reflected by the anomalous CM chondrite Bells. We further argue that although MRCCs likely accreted later than CM chondrites, CR chondrules must have initially formed from a reservoir spatially separated from CM chondrules. Finally, we hypothesize on the nature of the spatial barrier separating these reservoirs. 相似文献