摘要:

AbstractA 20 m Pleistocene section at Cala Salada, Ibiza, exposes three eolianites with interbedded silts and gravels. The basal eolianite has steep cross beds and represents a migrating dune, the upper two lack steep cross beds but contain abundant rhizomorphs and represent calcareous sand trapped by vegetation. Internal moulds of non‐marine molluscs occur only in the lower silts and the base of the middle eolianite. Within the lower silts are two cycles of upwards increasing diversity and abundance followed by local extinction, which probably reflect local ecological changes rather than major climatic fluctuations.The fauna contains eleven species, includingTudorella ferrugineahitherto known only from the eastern Balearics, and an extremely small form ofRumina decollat

ISSN:0072-1050    

DOI:10.1002/gj.3350170302

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractMajor element composition of the available analysed pelitic rocks of the Dalradian of Scotland is examined in relation to geographical position, mineralogy, metamorphic grade and stratigraphy. Some of the large variations found are due to geographical position, possibly reflecting different provenance. A major compositional difference exists between the two lower Barrovian metamorphic zones and the four higher zones. This is considered to be a reflection of the original sedimentary composition and large scale metasomatism is not considered likely.

ISSN:0072-1050    

DOI:10.1002/gj.3350170303

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

摘要:

AbstractThe ophiolitic sequence which crops out along the Aspropotamos Valley, Northern Pindos, Greece is composed from the bottom to the top of cumulates, dolerites, basaltic lavas, upper pillow lavas with basaltic/andesitic composition, and scarce basaltic dykes. The intrusive sequence, which is the subject of the present paper, exhibits magmatic layering more pronounced at the bottom than at the top where isotropic gabbros occur; they grade into the overlying dolerites. Troctolites with rare ultramafites prevail in the lower section and olivine gabbros in the upper section; at the top two‐pyroxene gabbros appear. The rocks are mainly adcumulates and mesocumulates with subordinate heteradcumulates. The cumulus phases separated in the order: olivine and Cr‐spinel, plagioclase, clinopyroxene, orthopyroxene. Olivine, plagioclase and pyroxenes frequently exhibit adeumulus overgrowth. Intercumulus phases may be plagioclase, clinopyroxene, orthopyroxene, pale brown amphibole and magnetite. Where pore material is present, it is composed of plagioclase, clinopyroxene, orthopyroxene, hornblende and ores. Cr‐spinel occurs mainly at the bottom of the sequence (Cr2O3between 30·5 and 39·8 per cent), whilemagnetiteappears as a very rare phase in the upper section. Olivine, orthopyroxene, clinopyroxene exhibit slight cryptic variation (Mg × 100/(Mg + Fe) in the range 90–79, 90–70, 93–72 respectively). The investigated dolerites are non‐cumulus rocks where clinopyroxene may be more magnesian than in the uppermost gabbros. The cumulate sequence and dolerites underwent variable but generally slight spilitization, in contrast to the overlying lavas. The sequence was generated through crystal accumulation probably from periodic pulses of tholeiitic magma; newly injected magma batches mixing with magma fractions already differentiated in the magma chamber. The high fluid pressure evidenced by the fluid inclusions in plagioclase and the whole chemical trend of the cumulate sequence are consistent with a genesis above a subduction zone, as already hypothesized for the

ISSN:0072-1050    

DOI:10.1002/gj.3350170304

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170305

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170306

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170307

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170309

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170311

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170312

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY

ISSN:0072-1050    

DOI:10.1002/gj.3350170313

出版商:John Wiley&Sons Ltd    

年代:1982

数据来源: WILEY