Papers by Liliane Janikian
Proceedings of the International Ocean Discovery Program, 2019
Scientific Reports, 2019
Young rifts are shaped by combined tectonic and surface processes and climate, yet few records ex... more Young rifts are shaped by combined tectonic and surface processes and climate, yet few records exist to evaluate the interplay of these processes over an extended period of early rift-basin development. Here, we present the longest and highest resolution record of sediment flux and paleoenvironmental changes when a young rift connects to the global oceans. New results from International ocean Discovery Program (IODP) Expedition 381 in the Corinth Rift show 10s-100s of kyr cyclic variations in basin paleoenvironment as eustatic sea level fluctuated with respect to sills bounding this semiisolated basin, and reveal substantial corresponding changes in the volume and character of sediment delivered into the rift. During interglacials, when the basin was marine, sedimentation rates were lower
Precambrian Research, 2015
Evolução tectônica e estratigráfica do Grupo Santa Bárbara (Ediacarano) na Sub-Bacia Camaquã Cent... more Evolução tectônica e estratigráfica do Grupo Santa Bárbara (Ediacarano) na Sub-Bacia Camaquã Central, RS, sul do Brasil: registro de sedimentação continental na assembléia do Gondwana Tectonic and stratigraphic evolution of Santa Bárbara Group (Ediacaran) in the Central Camaquã sub-basin, RS, southern Brazil: record of continental sedimentation on the Gondwana assemblage Resumo: O Grupo Santa Bárbara (Ediacarano) na Sub-Bacia Camaquã Central é representado por sucessão de depósitos arenosos e rítmicos flúvio-lacustres e depósitos conglomeráticos de leques aluviais que passam lateralmente a planícies aluviais entrelaçadas distais, compondo ciclos progradacionais-retrogradacionais. O Grupo Santa Bárbara apresenta mais de 2000 m de espessura, com excelentes exposições nas regiões das Minas do Camaquã e de Bom Jardim. Estudos estratigráficos de paleoambientes, paleocorrentes e de proveniência realizados possibilitaram a seguinte sub-divisão do Grupo Santa Bárbara, a partir da base: (i) ...
13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013, 2013
Revista Brasileira de …, 2008
The Camaquã Group is composed of sedimentary and volcanogenic successions that crop out in the so... more The Camaquã Group is composed of sedimentary and volcanogenic successions that crop out in the south-central portion of the Rio Grande do Sul State (southern Brazil). This supergroup is partially covered by Paraná Basin units and has been divided into sub-basins by the uplift of basement highs. This post-depositional tectonic segmentation, and the lithologic similarity among sedimentary successions of different stratigraphic levels makes it difficult to establish a formal lithostratigraphic column of the Bom Jardim Group without detailed field work. This paper presents a review of the lithostratigraphy of the Bom Jardim Work in its type-area, constituted by siliclastic, volcanic (basalts, andesites and rhyolites) and volcaniclastic rocks grouped in three units, with transitional contacts among each other.
Abstract LITHOSTRATIGRAPHY, DEPOSITIONAL SYSTEMS AND ICHNOFOSSILS OF THE CAACUPÉ GROUP (ORDOVICIA... more Abstract LITHOSTRATIGRAPHY, DEPOSITIONAL SYSTEMS AND ICHNOFOSSILS OF THE CAACUPÉ GROUP (ORDOVICIAN OF THE PARANÁ BASIN) IN THE CORDILLERA DE DOS ALTOS, EASTERN PARAGUAY The Caacupé Group is composed of sandstones and ...
RESUMO Estruturas induzidas por abalos sísmicos descobertas em afloramento da Formação Santa Bárb... more RESUMO Estruturas induzidas por abalos sísmicos descobertas em afloramento da Formação Santa Bárbara, unidade superior do Grupo Camaquã (Neoproterozóico III-Cambriano Inferior), no Passo da Capela, próximo à Santana da Boa Vista (RS), são aqui descritas. Tratam-se de falhas de componente normal e estruturas de liqüefação de sedimentos, ambas relacionadas à atividade sísmica sin-sedimentar. A análise estrutural das falhas de quatro gerações distintas indicou persistente direção de distensão segundo WNW-ESSE, ortogonal à orientação da bacia. Tal direção, associada aos dados regionais de proveniência e paleocorrentes nos depósitos da Formação Santa Bárbara, permite postular a vigência de regime tectônico distensivo durante o preenchimento desta unidade na Bacia do Camaquã, particularmente em sua sub-bacia oriental.
Precambrian Research
Precambrian Research j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t ... more Precambrian Research j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / p r e c a m r e s Columbia revisited: Paleomagnetic results from the 1790 Ma colider volcanics (SW Amazonian Craton, Brazil) a b s t r a c t In an attempt to improve our understanding of the Paleoproterozoic geodynamic evolution, a paleomag-netic study was performed on 10 sites of acid volcanic rocks of the Colider Suite, southwestern Amazonian Craton. These rocks have a well-dated zircon U–Pb mean age of 1789 ± 7 Ma. Alternating field and ther-mal demagnetization revealed northern (southern) directions with moderate to high upward (downward) inclinations. Rock magnetism experiments and magnetic mineralogy show that this characteristic magne-tization is carried by Ti-poor magnetite or by hematite that replaces magnetite by late-magmatic deuteric alteration. Both magnetite and hematite carry the same characteristic component. The mean direction (Dm = 183.0 • , Im = 53.5 • , N = 10, ˛ ...
The Amazonian Craton represents an important piece in the Paleoproterozoic paleogeography of the ... more The Amazonian Craton represents an important piece in the Paleoproterozoic paleogeography of the Earth. This study presents paleomagnetic data obtained on well-dated (U-Pb) 1790 Ma mafic sills from the Avanavero magmatism in northern Amazonian Craton (Guiana Shield). AF and thermal treatments revealed southeastern, low downward/upward inclination, remanent magnetization directions that are carried by moderate to high-H c and high-T B Ti-poor titanomagnetite. The site mean directions cluster around the mean D m = 138.2 • , I m = −3.4 • (N = 13, ˛9 5 = 13.0 • ), which yields a robust paleomagnetic pole (AV pole) at 27.9 • E, 48.4 • S (A 95 = 9.6 • ) with a Q-value of 5. The characteristic component disclosed for the Avanavero sill matches that obtained for sediments collected along the baked contact and are distinct from those away from the sill. The Avanavero directions are also significantly different from those obtained for younger units, with ages spanning from 1420 to 520 Ma, suggesting the sills carry a primary remanence. The Avanavero pole helps in constraining the paleogeography of the central pieces of Columbia. It is compatible with the Baltica and Amazonian Cratons SAMBA link in the Columbia Supercontinent at about 1780 Ma, but other configurations are also possible. When compared to other Paleo-to Mesoproterozoic paleomagnetic poles from the southern Amazonian Craton (Central Brazil Shield), our new paleomagnetic pole suggests intracratonic motions within the southern area of the Craton, probably after 1420 Ma ago. We tentatively suggest that these movements are related to the collision of the Paraguá Block with the proto-Amazonian Craton at about 1350-1320 Ma ago.
The Nuna supercontinent was probably assembled in the Paleoproterozoic, but its paleogeography an... more The Nuna supercontinent was probably assembled in the Paleoproterozoic, but its paleogeography and the timing for its demise are still a matter of debate. A paleomagnetic and geochronological study carried out on the Mesoproterozoic Nova Guarita dyke swarm (northern Mato Grosso State, SW Amazonian Craton) provides additional constraints on the duration of this supercontinent. Paleomagnetic AF and thermal treatment revealed south/southwest (northeast) magnetic directions with downward (upward) inclinations for 19 analyzed sites. These directions are carried by PSD magnetite with high unblocking temperatures as indicated by additional magnetic tests, including thermomagnetic curves, hysteresis loops and the progressive acquisition of isothermal remanence in selected samples. A positive contact test with the host granite in one of the studied dykes further attests to the primary origin of the characteristic magnetic component. A mean site direction was calculated at D m = 220.5 • , I m = 45.9 • (˛9 5 = 6.5 • , K = 27.7), which yielded a paleomagnetic pole located at 245.9 • E, 47.9 • S (A 95 = 7.0 • ). 40 Ar/ 39 Ar dating carried out on biotites from four analyzed dykes yielded well-defined plateau ages with a mean of 1418.5 ± 3.5 Ma. The Nova Guarita pole precludes a long-lived Nuna configuration in which Laurentia, Baltica, North China, and Amazonia formed a long and continuous block as previously proposed for the Paleoproterozoic. It is nevertheless fully compatible with a SAMBA (Amazonia-Baltica) link at Mesoproterozoic times.
During the Ediacaran, southern Brazil was the site of multiple episodes of volcanism and sediment... more During the Ediacaran, southern Brazil was the site of multiple episodes of volcanism and sedimentation, which are best preserved in the 3000 km 2 Camaquã Basin. The interlayered sedimentary and volcanic rocks record tectonic events and paleoenvironmental changes in a more than 10 km-thick succession. In this contribution, we report new U-Pb and Sm-Nd geochronological constraints for the 605 to 580 Ma Bom Jardim Group, the 570 Ma Acampamento Velho Formation, and a newly-recognized 544 Ma volcanism. Depositional patterns of these units reveal the transition from a restricted, fault-bounded basin into a wide, shallow basin. The expansion of the basin and diminished subsidence rates are demonstrated by increasing areal distribution and compressed isopachs and increasing onlap of sediments onto the basement to the west. The Sm-Nd isotopic composition of the volcanic rocks indicates mixed sources, including crustal rocks from the adjacent basement. Both Neoproterozoic and Paleoproterozoic sources are indicated for the western part of the basin, whereas only the older Paleoproterozoic signature can be discerned in the eastern part of the basin.
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Papers by Liliane Janikian