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Alexander Is land sed imentary rocks 1 . F irs t publ ished use Knowles , P . H. Geology of Southern Palmer Peninsula , Antarc t ica : Am. Ph il . Soc . Proc . 89 ( 1) , p . 132-145, 1945 . 2 . De finit ion Sedimentary rock was found in s itu at latitude 72° 08 ' S . , l ong itude 68° 451 W . on the southernmost peak of Al exander I Is land . The rock consisted of un iform hor izontal s trata of compac t mudstone , graywacke , arkose , and coarse c ongl omerate . " (Knowles , 141) 3 . Type sec t ion a. Location Southernmo s t peak of Alexander I I s land b . Lithol ogy Nonmar ine mudstone , graywacke , arkose and coarse c onglomerate . 1) mud s tone - minute quartz , fe ldspar and b io t i te in a hydrous aluminum s i l icate groundmas s . 2) cong lomerate - subangular pebbles up to 1/2 " in a quar tz, fe ldspar and mica groundmass . 3) arkose - medium-grained , gray rock composed of a subangular quartz , orthoc lase and andes ine in a ferruginous ly cemented groundmas s . c . Evidence of age Nearby fos s i l localit ies sugges t a Jurass ic or Cret aceous age . Base Gab rie l Gonzalez Vide la andes i te 1 . Firs t published use Halpern , M. The geology of Base Gab rie l Gonzalez Videla, Ant arctica: Arct ic, 15 , p . 23 1-23 7 , 1962 . 2 . Definit ion "The multiple andes i te s ills or flows of Islas 'Lomnitz' and 'Dot t' are about 200 metre s th ick, Thicknes s of ind ividual sheet s is extremely difficult to de termine because of intense fracturing and poor exposures due to snow and guano cover. Where measurable shee ts are 4 t o 7 metres thick and dip s teeply s outh . " (Halpern , 232) - 1 -
