Fluvial styles, palaeohydrology and modern analogues of an exhumed, Cretaceous fluvial system: Cerro Barcino Formation, Cañadón Asfalto Basin, Argentina

Abstract Superb surface exposures of a fluvial palaeochannel-belt 2–5 km wide and 13 km long occur in Cretaceous sedimentary rocks of the Cerro Barcino Formation (Las Plumas Member), Chubut Group, Canadon Asfalto Basin, Argentina. The exceptional plan-view exposures of fluvial sandbodies allowed identification of a large number of WNW–ESE sinuous ridges that represent high-sinuosity, braided and low-sinuosity fluvial palaeochannels, crevasse and chute palaeochannels, and crevasse-splay deposits. Predominance of low-sinuosity palaeochannels and low values of the width/thickness ratio of most them suggest high stability of their margins, probably controlled by the cohesiveness of tuffaceous floodplain deposits. Morphological and sedimentological observations provide evidence of abrupt lithofacies changes in palaeochannel fills, fine-grained intercalations in multi-storey palaeochannels and occurrence of different fluvial styles, implying temporal/spatial variations in palaeodischarge and/or slope conditions. Comparison of the near-identical plan view morphology of the Cretaceous palaeochannel belt with the nearby Chubut River, plus the comparison of palaeohydrological data of the exhumed palaeochannels with hydrological data from this modern analogue, gives evidence of a very similar fluvial behaviour. This provides an integrative tool to be employed in the study of other ancient fluvial successions, including the reconstruction of palaeofluvial hydrological parameters in planetary geology.

[1]  S. Schumm,et al.  Geomorphic and sedimentary response of rivers to tectonic deformation: a brief review and critique of a tool for recognizing subtle epeirogenic deformation in modern and ancient settings , 1999 .

[2]  E. Musacchio,et al.  OSTRACODOS NO MARINOS Y CAROFITAS DEL CRETACICO INFERIOR EN LAS PROVINCIAS DE CHUBUT y NEUQUEN, ARGENTINA 1. OSTRACODOS y CAROFITAS DEL GRUPO CHUBUT 2. "RAYOSOANA QUILlMALENSIS" NOV. GEN., NOV. SP., DE LA FORMACION RAYOSO, NEUQUEN , 1975 .

[3]  J. Carballido,et al.  New chelid turtles of the lower section of the Cerro Barcino formation (Aptian-Albian?), Patagonia, Argentina , 2011 .

[4]  James R. Zimbelman,et al.  Evaluation of paleohydrologic models for terrestrial inverted channels: Implications for application to martian sinuous ridges , 2009 .

[5]  J. Maizels.  Raised channel systems as indicators of palaeohydrologic change: a case study from Oman , 1990 .

[6]  David E. Eby,et al.  Exhumed Paleochannels in Central Utah—Analogs for Raised Curvilinear Features on Mars , 2007 .

[7]  J. Köykkä.  The sedimentation and paleohydrology of the Mesoproterozoic stream deposits in a strike–slip basin (Svinsaga Formation), Telemark, southern Norway , 2011 .

[8]  L. King,et al.  South African Scenery , 1963 .

[9]  R. Miller.  Drainage Lines in Bas-Relief , 1937, The Journal of Geology.

[10]  M. Slater,et al.  Vertical and lateral building of river sandstone bodies, Ebro Basin, Spain , 1979, Journal of the Geological Society.

[11]  S. Schumm.  PATTERNS OF ALLUVIAL RIVERS , 1985 .

[12]  C. W. Carlston,et al.  The relation of free meander geometry to stream discharge and its geomorphic implications , 1965 .

[13]  P. Vickers-Rich,et al.  Dinosaur remains from the Lower Cretaceous of the Chubut Group, Argentina , 2003 .

[14]  L. V. van Vliet,et al.  Parameterization of meander-belt elements in high-resolution three-dimensional seismic data using the GeoTime cube and modern analogues , 2007, Geological Society, London, Special Publications.

[15]  Roger M. H. Smith.  Morphology and Depositional History of Exhumed Permian Point Bars in the Southwestern Karoo, South Africa , 1987 .

[16]  S. Schumm.  River adjustment to altered hydrologic regimen - Murrumbidgee River and paleochannels, Australia , 1968 .

[17]  S. Ouchi.  Response of alluvial rivers to slow active tectonic movement , 1985 .

[18]  Marc B. Edwards,et al.  Paleochannel geometry and flow patterns determined from exhumed Permian point bars in north-central Texas , 1983 .

[19]  I. Brookes.  Palaeofluvial estimates from exhumed meander scrolls, Taref Formation (Turonian), Dakhla Region, Western Desert, Egypt , 2003 .

[20]  A. Miall.  The Geology of Fluvial Deposits: Sedimentary Facies, Basin Analysis, and Petroleum Geology , 1996 .

[21]  G. Williams.  River meanders and channel size , 1986 .

[22]  A. Bumby,et al.  Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2 1.9 Ga Waterberg Group, South Africa , 2006 .

[23]  W. K. Hamblin,et al.  Recognition of ancient sedimentary environments , 1972 .

[24]  C. C. Reeves.  Pliocene channel calcrete and suspenparallel drainage in West Texas and New Mexico , 1983, Geological Society, London, Special Publications.

[25]  J. Bridge.  Description and interpretation of fluvial deposits: a critical perspective , 1993 .

[26]  S. Schumm.  Speculations Concerning Paleohydrologic Controls of Terrestrial Sedimentation , 1968 .

[27]  E. Musacchio.  CAROFITAS DEL CRETACICO INFERIOR EN SEDIMENTITAS "CHUBUTENSES" AL ESTE DE LA HERRERIA, CHUBUT , 2013 .

[28]  T. Gardner.  Paleohydrology and Paleomorphology of a Carboniferous, Meandering, Fluvial Sandstone , 1983 .

[29]  Marcela I. Cosarinsky,et al.  Rhizolith balls from the Lower Cretaceous of Patagonia: Just roots or the oldest evidence of insect agriculture? , 2010 .

[30]  Gary Nichols,et al.  Processes, facies and architecture of fluvial distributary system deposits , 2007 .

[31]  M. Gibling.  Width and Thickness of Fluvial Channel Bodies and Valley Fills in the Geological Record: A Literature Compilation and Classification , 2006 .

[32]  J. Köykkä.  Precambrian alluvial fan and braidplain sedimentation patterns: Example from the Mesoproterozoic Rjukan Rift Basin, southern Norway , 2011 .

[33]  G. Cladera,et al.  Controles estratigráficos en la preservación de restos de vertebrados en la formación Cerro Barcino (Cenomaniano), provincia del Chubut , 2004 .

[34]  M. Gordon Wolman,et al.  Fluvial Processes in Geomorphology , 1965 .

[35]  Á. Marcuello,et al.  Exhumed channel sandstone networks within fluvial fan deposits from the Oligo‐Miocene Caspe Formation, South‐east Ebro Basin (North‐east Spain) , 2010 .

[36]  I. Rutherfurd,et al.  Pre-cutoff morphology of the lower Mississippi river , 1994 .

[37]  J. Costa.  Paleohydraulic reconstruction of flash-flood peaks from boulder deposits in the Colorado Front Range , 1983 .