603

to those of borings and are selectively filled witlibone chips, occur sporadically just below (about within 70 cm downwards) the scapula. Some burrows are solitary, and some are colonial. Burrow direction is also diverse, and some burrows are interlaced forming network. The bone-borings and related bone chip-filled burrows postdated bone weathering- including cracking, fracturing, breccia tion, and disintegration, which indicates that Dapyeongri bone-borers preferred to feed upon dried skeleton.

These traces of bone-borings and bone chip-filled burrows indicate that the Dapyeongri dinosaur carcasses were exploited by carrion insects, and provide evidence that dermestid beetles played an important role as the last scavenger of dinosaur carcasses during the Early Cretaceous. Such scavenging of carrion insects under dry climate may deteriorate the dinosaur fossil preservation in the Cretaceous deposits. The behaviour of Dapyeongri bone- borers/burrowers is compared with that of dung beetles documented from the Upper Cretaceous Two Medicine Formation (Chin and Gill, 1996), in caching subterranean burrows with organic matter transported froin surface. In

terms of trophic interaction between dinosaurs and insects related with paleoclima tic condition, dermestid beetles might have utilized dried dinosaur carcasses in dry seasons under arid and seasonal climate (this study and Upper Cretaceous Two Medicine Formation; Rogers, 1992), whereas dung beetles utilized herbivorous dinosaur dungs in rainy seasons under semiarid/monsoonal climate (Upper Cretaceous Two Medicine Formation; Chin and Gill, 1996) (Fig. 2). These unique trace fossils thus provide another evidence for understanding Cretaceous tropliic interaction between dinosaurs and insects.

References

Chin, K. and Gill, B.D. (1996) Dinosaurs, dung beetles, and conifers: participants in a Cretaceous food web. Palaios, v.

Rogers, R.R. (1992) Non-marine borings in dinosaur bones from the Upper Cretaceous Two Medicine Formation, northwestern Montana. J . Vert. Paleontology, v.12,

11, pp. 230-257.

pp. 528-531.

Goridicinrzn Rrscnrck, l? 2, No. 4, p p . 603-604. 0 1999 lrztc~riintronnl Assocmtioiz f o r Goizdiuonn Rescnrdi, Jnpnrz. ISSN: 1342-937X GR

Goizdwaiia Research

Geochemical Studies on the from Kodaikanal,

Sapphirine-Granulites South India

Divya Prakash and Anant Shastry

Departnzent of Geology, Bnnnras Hindu Uniuersity, Vnranasi 221 005, lndia

The importance of the Kodaikanal area stems mainly from its distinction as one of the sapphirine-bearing terranes. Sapphirine- granulites are located at 15 km milestone NE of Kodaikanal, on the left hand side of the Kodaikanal- Palani road near Perumal malai in an abandoned quarry. Scattered rock pieces around the quarry contain sapphirine, orthopyroxene, sillimanite, cordierite, garnet, spinel, phlogopite, and K-feldspar, in a variety of assemblages.

The bulk composition of sapphirine granulites from Kodaikanal is unusual. These rocks are rich in A1,0,, (MgO+FeO), but poor in CaO. SiO, content is rather high compared to most silica-deficient granulites and (Na,O+K,O) content is also raised on account of the presence

of phlogopite, k-feldspar and plagioclase. The popular "restite" origin for the silica-deficient granulites does not explain the higher concentration of SiO, and (Na,O+K,O). In the absence of major extraction of silicate melt, an alternative mechanism of vapour absent dehydration melting reactions has been proposed as plausible method for the development of granulite facies assemblages. Calculations show that a rock with initial 10 vol % biotite would produce only small (10-20%) of melt at elevated temperature (4350°C)) so that melt extraction is probably not effective in granulite facies desiccation. On similar lines, it is possible to write a dehydration melt reaction for Kodaikanal sapphirine granulites:

604

Biotite t Sillimanite = Sapphirine + Cordierite + K- of sapphirine-bearing rocks of Kodaikanal, but future experiments are required to substanti'i te this

Such a mechanism suitably explains the bulk chemistry hypothesis. feldspar + L

Goildzuaiza Resenrrk, V. 2 , NO. 4, p p . 604-606. 0 1999 Iizterimfioiial Association for Goiidrvaiza Resenrch, Japai'z. I SSN: 1342-937X GR

Characteristics and Origin of Aluminous A-type Granitoids from Southwestern India

H.M.Raj es h

Department of Geosciences, Fnczilfy of Science, Osaka City University, Siigiinoto 3-3-138, Sitmi?loslzi-Kzr,Osakn 558-8585, Jnpnn, e-nznil:r.ajesizOsci.osakn-cti.nc.jp

A suite of alkali granite and syenite plutons preserving evidence for a prominent Pan-African felsic magma tic event intrudes the Proterozoic granulite facies terrains of southwestern part of the Indian Peninsula (Fig.1). These plutonic masses are E-W or WNW-ESE to NW-SE elongated elliptical bodies showing sharp contacts with the country rocks, viz, migmatized felsic gneisses (garnet-biotite gneiss, biotite gneiss, hornblende- biotite gneiss or biotite- hornblende gneiss) and/or charnockites (ortliopyroxene- bearing quartzo- feldspathic rocks of either igneous or me tamorphic origin). Significantly these intrusives show spatial association with regional lineaments, implying that the orientation of these intrusives is directly controlled by the local fault pattern, and indirectly controlled by the rate of magma injection and heat loss into the country rocks. The proximity of the plutons to the edges or junctions of these megafault of continental scale suggests that the magma generation and emplacement could be related to the formation and/or reactivation of these faults. Importantly, the plutons themselves are unsheared and largely unaffected by later deformational events, indicating the post-tectonic (anorogenic) nature of the magma tism.The field relations and undeformed igneous textures of most of these intrusions suggest that the melts migrated during the deformation in the associated shear zone/fault lineament, but crystallized after the deformation had ceased, leading to the general lack of deformational features. Hence the ages of these granitoid intrusions should correspond closely to the conditions of deformation of the shear zone/fault lineament.

5

Fig

L \

I'

LEGENR \ (

----- Major fault-lineaments 2 Alkali granite/syenite plutons , '\

', i,r

General outline of southwestern India (mainly the Kerala State) showing the distribution of alkali granite and syenite plutons and their spatial relationship to regional fault. lineaments. Most of these alkali granitoids are A-type granitoids.