The relationship of the orogeny with the
Achala and
Cerro Asperobatholiths of central Argentina is not fully understood. These Devonian batholiths are possibly of post-orogenic character.[5][6]
Outcrops and sediments
The Famatinian orogen's main
outcrops lie in
Sierras Pampeanas in
northwestern Argentina.[1][7] Only the western part of Sierras Pampeanas bears evidence of the Famatinian orogeny; the eastern parts appear to have been largely unaffected.[1] In
northern Chile the
Belén Metamorphic Complex is thought to have been subject to metamorphism that was "time-equivalent" to the Famatinian orogeny in the early Paleozoic.[7] It can this be considered part of the orogen in a broad sense.[7] To the south in
La Pampa Province, outcrops associated with the orogeny are scarce since most of that region has become blanketed by much more recent
Quaternarysediments.[8]
In Peru's
Cordillera Oriental a "Famatinian" orogeny exists which is coeval with the classical Famatinian orogeny found further south. In the time-span from 480 Ma to 435 Ma (Late Cambrian to Silurian) rocks of Cordillera Oriental were deformed and a magmatic arc developed.[9]
Towards what is now the east of the Famatinian magmatic arc a
Precambriansedimentary basin developed into a
back-arc basin during the
Ordovician. This basin went from Peru, through Bolivia to northwestern Argentina. The basin collected sediments from the Famatinian orogen and arc and while it did not contain
oceanic crust it was a marine basin.[10]
It has been suggested that the coeval
AppalachianTaconic orogeny is the "northward" continuation of the Famatinian orogeny.[note 2] This has been explained by adding that the continent
Laurentia could have
collided with
Gondwana (at what is today western South America) in early Paleozoic times due to the
closure of the
Iapetus Ocean.[13] Supporting this hypothesis is the suggestion that the orogens have "truncated ends" that can be matched and that both share the commonality of having
carbonateplatformsediments at what is today their western side.[13][14] Further, in the mentioned sediments both orogens host similar
Olenellid trilobite faunas, something that is not expected to be unless both orogens had some sort of contact.[13] This is because trilobites are unable to cross deep
ocean basins.[15] According to this view the
Cuyaniaterrane would be an
allochthonous block of Laurentian origin that was left in Gondwana after the continents went apart. But such views are not unchallenged since Cuyania is alternatively suggested to have drifted across Iapetus Ocean as a
microcontinent starting in Laurentia and
accreting then to Gondwana. Further a third model claims Cuyania is
para-autochthonous and arrived at its current place by
strike-slip fault movements starting not from Laurentia but from another region of Gondwana.[12] The fact that Precordillera terrane has many trilobite
genera in common with Laurentia but many species are endemic have led to some
differing interpretations on what paleogeographic and tectonic history conditions are plausible explanations for this biogeography.[15]
Notes
^All coordinates in this article are in relation to present-day geography and not to the past disposition of continents,
terranes and oceans.
^In other words: what is at present the northern end of the Famatinian orogen would have been connected with what is currently the southern end of the Taconic orogen.
^Lira, Raúl; Kirschbaum, Alicia M. (1990). "Geochemical evolution of granites". In Mahlburg Kay, Suzanne; Rapela, Carlos W. (eds.). Plutonism from Antarctica to Alaska. Geological Society of America Special Paper. Vol. 241. pp. 67–76.
^
abcHervé, Francisco; Faundez, Victor; Calderón, Mauricio; Massonne, Hans-Joachim; Willner, Arne P. (2006). "2. Metamorphic and plutonic basement complexes". In Moreno, Teresa; Gibbons, Wes (eds.). Geology of Chile. Geological Society of London. pp. 5–19.
ISBN9781862392199.
^
abChernicoff, Carlos J.; Zappettini, Eduardo O.; Santos, João O.S.; Allchurch, Shelley; McNaughton, Neal J. (2010). "The southern segment of the Famatinian magmatic arc, La Pampa Province, Argentina". Gondwana Research. 17 (4): 662–675.
Bibcode:
2010GondR..17..662C.
doi:
10.1016/j.gr.2009.10.008.
^Bahlburg, Heinrich; Vervoort, Jeffrey D.; DeFrane, S. Andrew; Carlotto, Victor; Reimann, Cornelia; Cárdenas, José (2011). "The U-Pb and Hf isotope evidence of detrital zircons of the Ordovician Ollantaytambo Formation, southern Peru, and the Ordovician provenance and paleogeography of southern Peru and northern Bolivia". Journal of South American Earth Sciences. 32 (3): 196–209.
Bibcode:
2011JSAES..32..196B.
doi:
10.1016/j.jsames.2011.07.002.
^Dalla Salda, Luis H.; López de Luchi, Mónica.; Cingolani, Carlos A.; Varela, Ricardo (1998). "Laurentia-Gondwana collision: the origin of the Famatinian-Appalachian Orogenic Belt (a review)". In
Pankhurst, R.J.; Rapela, C.W. (eds.). The Proto-Andean Margin of Gondwana. Vol. 142. Geological Society, London, Special Publications. pp. 219–234.