Geological investigation of the Yahgan Formation (Upper Mesozoic) and associated igneous rocks of Navarino Island, Southern Chile

Abstract

Navarino Island is composed mainly of a sequence of geosynclinal sediments-the Yahgan Formation-at least 3,000 metres thick and of probable Early Cretaceous age. The main sediments are greywackes, argillites, and cherts. Calcareous concretions are characteristic of some horizons but are nowhere abundant. Many coarser-grained sediments contain abundant andesitic to basaltic debris, indicating widespread contemporaneous volcanic activity. Fossils are rare and comprise poorly preserved Radiolaria, fragmentary plant remains, and imprints of Inoceramus. Recrystallisation is evident in many rocks; in particular, secondary prehnite is characteristic, especially in the coarser sediments. The formation includes several thick quartz dolerite sills. The largest of these forms a conspicuous east-west chain of serrated peaks, the so-called Dientes de Navarino. The south-west part of the island and the nearby Bertrand Island are composed of altered basic igneous rocks, believed to be contemporaneous with the Yahgan Formation sediments.Dioritic rock, belonging to the Andean intrusive series (Patagonian Batholith) and considered to be Upper Cretaceous, cuts the folded Yahgan Formation, more especially in the west and south parts of the island.The sediments are moderately to strongly folded and dip mainly towards the south. In many places, however, minor thrusts and asymmetric folds are present, and their attitudes suggest that orogenic stress was towards the north.

Detrital zircon SHRIMP U–Pb age study of the Cordillera Darwin Metamorphic Complex of Tierra del Fuego: sedimentary sources and implications for the evolution of the Pacific margin of Gondwana

“…The RVB was the depositional locus for the thick succession of Lower Cretaceous 85 volcaniclastic sedimentary rocks of the Yaghan Formation (Katz & Watters 1966 (Fig. 4).…”

The Scotia Arc and Antarctic Margin

“…It contains a high proportion of thickly bedded graywackes with volcanic debris, and basic lavas (Katz and Watters, 1966 (Katz and Watters, 1966) and Neocomian ammonites (Haipern, 1972a;Halpern and Rex, 1972). As pointed out by Wilckens (1933, p. 324), Matthews (1959), and Katz and Watters (1966, p. 341-342), the Yahgan Formation is strikingly similar to the Cumberland Bay Series of South Georgia that is now about 1500 km to the east (but, see p. 207 and Fig.…”

“…As mentioned previously, M. K. Rickard and K. T. Burns (personal communication) have determined that the Serie Tobifera in Tierra dei Fuego is disposed in an asymmetrie anticline (with the pre-Tobifera basement complex as a core; see The structural geometry of the Yahgan Formation on Navarino Island, and the Cumberland Bay Se ries on South Georgia is similar. Asymmetrie folds with gently plunging axes are overturned northward on Navarino Island (Katz and Watters, 1966) (see Fig. 4), and northeastward on South Georgia (Trendall, 1959), both normal to the trend of the Scotia Are and from the Pacific side to the Atlantic side (Dalziel, 1 972a).…”

“…The Yahgan Formation (Kranck, 1932) of southernmost Tierra dei Fuego is over 3000 m thick on Navarino Island (Katz and Watters, 1966). It contains a high proportion of thickly bedded graywackes with volcanic debris, and basic lavas (Katz and Watters, 1966 (Katz and Watters, 1966) and Neocomian ammonites (Haipern, 1972a;Halpern and Rex, 1972).…”

Petrological vestiges of the Late Jurassic-Early Cretaceous transition from rift to back-arc basin in southernmost Chile: New age and geochemical data from the Capitán Aracena, Carlos III, and Tortuga ophiolitic complexes

“…Thus, the age of the ophiolites is indirectly constrained as Tithonian to by biofacies associations in the overlying sedimentary successions (Fuenzalida and Covacevich, 1988;Suárez et al, 1985). The ophiolites underwent seafloor-type hydrothermal metamorphism (Stern et al, 1976;Elthon and Stern, 1978) and were subsequently buried and obducted onto the margin of South America during the ensuing phases of Andean orogenesis in the mid-Cretaceous (Katz and Watters, 1966;Dott et al, 1977;Dalziel, 1981;Cunningham, 1994;Fildani et al, 2003;Fosdick et al, 2011;Calderón et al, 2012). Granitoids consisting of hornblende-biotite tonalite, granodiorite, and restricted monzonite and monzodiorite (Katz and Watters, 1966;Godoy, 1978;Allen, 1982) intruding the ophiolite complexes are of earliest Late Cretaceous age (Hervé et al, 1984Cunningham, 1994;Calderón et al, 2012).…”