El Paleogeno De La Cuenca De Magallanes: Bioestratigrafía Y Discontinuidades

Abstract

the Magallanes or Austral basin is shared by Argentina and Chile; both countries developed the knowledge on foraminifera in different timing and ways. these differences delayed the integration of the stratigraphical information from both parts of the basin. in Chile, the studies began in the ´40s in the national oil company EnAP and most of its reports remained unpublished until 1974, when a system of stages for correlation was proposed. this system, particularly for the Paleogene, was based on benthonic foraminifera because of the scarcity of planktonic forms. in Argentina, a first study on the Paleogene foraminifera from the Austral basin is published in the late 60s, and after several years devoted to publish and illustrate the Cretaceous foraminifera, the research has been again focused on the Paleogene since the end of the century. the integration of the knowledge from both sides of the international boundary, and particularly the gathering of the data on the scarce planktonic forms, have helped to correlate Argentinean and Chilean formations, pointing out the great difference between the thick Paleogene sequences in the Chilean Peninsula brunswick and the reduced Paleogene sequence, including more manifest and amplified unconformities, in the Argentinean Atlantic fuegian coast.the contact between the Maastrichtian and the danian by means of foraminifera is recognized in the northern part of the basin (Cerro dorotea formation), whereas in the southern part is not evident due to an unconformity in the mid-Paleocene and the dominant, not age diagnostic, flysch type assemblages. the Paleocene/Eocene turnover in calcareous assemblages exhibits a contrast between a cosmopolitan Midway type assemblage in the upper Paleocene (la barca/Chorrillo Chico formations) and an endemic early Eocene Austral assemblage that includes the first appearance of the genus Elphidium (Punta noguera/lower Agua fresca), and the genus Cribrorotalia in the Punta noguera formation. the lower 1 Consejo nacional de investigaciones Científicas y técnicas, Argentina. n.malumian@yahoo.com 2 laboratorio de Micropaleontología, instituto de la Patagonia, universidad de Magallanes, Chile. 3 servicio geológico Minero Argentino. Middle Eocene unconformity separates disaerobic and turbiditic paleoenvironments of the Paleocenelower Middle Eocene (la barca, Punta torcida/Chorrillo Chico, Agua fresca) from the aerobic shallow marine settings of the late Middle Eocene (leticia/tres brazos, boquerón). the sediments underlying the unconformity were deposited in a turbiditic marine paleoenvironment, with both restricted circulation and connection with the open sea, which was dominant from the Campanian up to the lower Eocene. the paleoenvironmental turnover is clearly reflected by the dominance of agglutinated and generally small foraminifera in the Campanian-lower Eocene in contrast with dominant large nodosariidae foraminifera associated to a bloom of crinoids in the late Mid Eocene. this turnover reveals changes in the morphology of the basin t...

Paleobiogeography of the Danian molluscan assemblages of Patagonia (Argentina)

“…13), or Danian (Malumián et al, 2013). In addition, palynological study recently conducted by Povilauskas (2010), indicates a Danian age for this unit.…”

Campanian-Eocene dinoflagellate cyst biostratigraphy in the Southern Andean foreland basin: Implications for Drake Passage throughflow

“…The sediment in the Rocallosa Formation is gradually fining upwards. Zircon dating suggests a late Maastrichtian age (67 Ma;Malumián et al, 2013). A hiatus has been suggested between the Rocallosa and the overlying Chorillo Chico Formation (Malumián et al, 2013).…”

“…We provide an overview of the lithostratigraphic formations in chronological order and their tentative ages based on earlier work (e.g., Thomas, 1949;Otero et al, 2012;Malumián et al, 2013). Table 2 presents a summary and reference to the localities (Fig.…”

“…The Fuentes Formation reflects voluminous sediment supply from the Andean orogeny (Charrier and Lahsen, 1969). Published age for the Fuentes Formation is early Maastrichtian (Malumián et al, 2013). The contact with the overlying formation has been a matter of debate: while Thomas (1949) suggested it was clearly non-conformable, Charrier and Lahsen (1969) put this into question.…”

New and little-known bryozoans from Monte León Formation (early Miocene, Argentina) and their paleobiogeographic relationships

“…Most of the Monte León Formation seems to have been deposited in a relatively low-energy shelf setting, with a gradual upward shallowing trend and an abundant supply of volcanic ash (Malumián, 1999).…”