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2 . Definition "The basaltic rocks of the ·Hut Point area are particularly rich in ultramafic inclus ions ⢠⢠⢠⢠Embayment textures and reaction effects are commonly displayed by olivine and pyroxene grains along the margins of the inclusions in contact with the basalt . Although textures are dominantly xenomorphic granular , petrofabric analys is of olivine indicatrix orientations show well-defined �1 girdles . " (Forbes , 39 ) 3 . Type sect ion a . Location Hut Point Peninsula , Ross Is land , Antarctica b . Lithology Basalt , rich in ultramafic inclus ions - alkali -olivine variety. Phenocrystal olivine and t itanaugite in a fine-grained groundmaas of titanaugite , olivine , titaniferous magnetite and rare Ddcrolites of calcic plagioclase . Forbes , R. B. and s. Bamno . NiCkel-iron content of peridotite inclusion and copate olivine from an alkali-olivine basalt : Am. Min. 51 , P ⢠139-140 , 1966 . Is la "Dot�r argillaceous metaconglomerate 1 . Pirst published use Halpern, M. The geology of Base Gabriel Gonzalez Videla , Antarctica : Arct ic , 15 , p. 231-237 , 196 2 . 2 . Definition "On Isla "Dott" , approximately 5 metres below the uppenD&t andes ite sheet , a 4-metre bed of metaconglomerate crops out . The metaconglomerate is composed of rounded granules and pebbles of quartz and subordinate sandstone and quartz diorite in a metamorphosed s ilty matrix. The matrix is carbonaceous and has flowed around the rock fragments . " (Halpern, 235 ) 3 . Type sect ion a. Location Is la 'bott' , off Danco Coast , Antarct ic Peninsula b . Thicknes s 4 meters - so -
c . Lithology Metaconglomerate with clasts of quartz , sands tone and quartz diorite ; garnet , magnet ite , b iotite and z ircon accessory . d . Evidence for age Field relat ions show it to be among oldest units in the area . Isla " Dott" porphyritic andes ite 1 . First published use Halpern , M. The geology of Base Gabriel Gonzalez Videla , Antarctica : Arct ic , 15 , p . 231-237 , 196 2 . 2 . Definition "The porphyritic andes ite occupies the southern half of Isla 1 Dott ' Whereas the southern t ip of the is land is cut by irregular dikes of fine -grained andes ite less than . 5 metre thick . " " In hand specimen , about 45% of the rock is composed of l igat grey plagioclase feldspar phenocrysts as long as 2 mm in a fine-grained , dark grey matrix . " (Halpern , 232 ) 3 . Type section a. Location Isla " Dott' , Base Gabriel Gonzalez Videla , on Danco Coast , Antarctic Peninsula b . Lithology Calcic andes ine with albite and carlsbad-albite twinning . Rare crys tals are zoned. The fine -grained ground mass includes 2% of quartz �kit ically intergrown with sausser it ized feldspar . Pale green chlorite and amphibole total 7% of the rock and lesser accessory minerals ·include epidote , apatite , z ircon , magnet ite and ilmenite . The matrix has a pronounced flow structure and is compos ed mainly of microlites and altered microcrys talline feldspar . (Halpern, 232 ) Isla 1 1Lomnitz11 argillite 1. First published use Halpern, M. The Geology of Base Gabriel Gonzalez Videla , - 51 -
Antarctica : Arct ic , 15 , p . 231-237 , 1962 . 2 . Definition "On the central western shoreline of Isla ' Lomnitz ' a 6 -metre sect ion of metamorphosed , finely interlaminated s iltstone and shale crops out . The beds are nearly vertical and tops , as indicated by fine -scale cross -laminae , are to the south . Laminae are 1 Dill to 1 . 5 em thiCk and have very sharp contacts . Micrograded bedding is present in the darker laminae . " (Halpern , 235 ) 3 . Type section a . Location Central wes tern shoreline of Isla 'Lomnitz ' , off the Danco Coas t , Antarctic Peninsula b . Thickness 6 meters c . Lithology Metamorphosed , finely interlaminated s ilts tone and shale , micrograded bedding , load casta , microfaulting and delicate croas �laminae are preserved , quartz grains recrystallized and moaaio around chlorite and sericite flakes . d . Relation to other units Surrounded by Base Gabriel Gonzalez Videla andes i te e . Evidence for age Field relations place it as one of oldes t units in the area. 4 . Remarks Cross -laminae indicate paleocurrents from the east -northeast . Isla 'Lomnitz ' quartz diorite 1. Fir�t published use Halpern , M. The geology of Base Gabriel Goualez Videla , Antarctica : Artie 15 , p . 231-237 , 1962 . - 52 -
2 . Definition "Quartz diorite intrudes the andes ite s ills or flows along the eastern coast of Isla 1 Lomnitz ' and crops out as a large intrus ive body on the mainland east of the islands . The quartz diorite is coarse and and even-grained , and is mottled green and light to medium grey . It is separable into 3 facies on the bas is of colour , compos ition , and grain s ize . (Halpern, 233 ) 3 . Type sect ion a . Location East coast of Is la "Lomnitz14 , off Danco Coas t , Antarct ic Peninsula b . Lithology Facies 1 of Danco Coast is medium grey with a greenish tinge and has a high mafic content . Cores of many of the plagioclase crystals in this facies are sausseritized. Facies 2 occurs along the east-central coast of Isla 11Lomnitz'' , where the quartz diorite is near the andes ites ; it is pink and green. A decrease in the amount of mafics to 8% and a small increase in alkali feldspar accounts for this color change . Plagioclase is much less altered . Facies 3 is a fine-grained facies . Orthoclase and plagioclase each comprise 30% of the rock with quartz about 30%. All facies display �kitic te tures as an intergrowth of andes ine (50%} , orthoclase ( 15%) , and quartz ( 15%) . Chlorite and amphibole up to 20% are present in light green tabular crys tals . c . Relation t o other units Intrudes Base Gabriel Gonzalez Videla andes ite . d . Evidence for age " ⢠⢠⢠poss ibly correlat ive with the post -Juras s ic 'Andean intrus ives ' of the Trinity Peninsula . " (Halpern , 234) . - 53 -
