Geology, Thermal Maturation, and Source Rock Geochemistry in a Volcanic Covered Basin: San Juan Sag, South-Central Colorado

AAPG Bulletin ◽  
1997 ◽  
Vol 81 (1997) ◽  
Author(s):  
Robbie Rice Gries, J. L. Clayton, a
2021 ◽  
Vol 124 ◽  
pp. 104773
Author(s):  
Yoav O. Rosenberg ◽  
Itay J. Reznik ◽  
Harold J. Vinegar ◽  
Shimon Feinstein ◽  
Yuval Bartov

2017 ◽  
Vol 112 ◽  
pp. 59-74 ◽  
Author(s):  
Yoav O. Rosenberg ◽  
Alexander Meshoulam ◽  
Ward Said-Ahmad ◽  
Lubna Shawar ◽  
Guy Dror ◽  
...  

2017 ◽  
Vol 10 ◽  
pp. 83 ◽  
Author(s):  
Erik Johnson Marsh

<p>La cerámica más temprana marca un hito en la historia humana de los Andes del sur. Este trabajo propone una aproximación de la edad de la cerámica más temprana mediante modelos cronológicos basados en la estadística bayesiana. En estos, se comparan 84 fechados radiocarbónicos y de termoluminiscencia de 49 sitios que abarcan dos áreas en Argentina dentro de las provincias de San Juan y Mendoza y tres áreas del norte semi-árido, centro y centro-sur de Chile. Los datos analizados indican un patrón llamativo de fechas similares en cuatro de las cinco áreas, con medianas entre 2100 y 2180 cal. AP (2250-1920, 68% probabilidad, límites iniciales), aunque algunos de los rangos de error son amplios. Se destaca la similitud de las fechas en una macrorregión que se extiende a lo largo de 1000 kilómetros (norte-sur) entre las 30° a 39°S y que contiene una gran variedad de ambientes. La coincidencia temporal resulta aún más llamativa porque el límite sur de agricultura en el continente Sudamericano se encuentra en estas áreas. Este trabajo pretende incentivar el interés de los investigadores en la excavación y el fechado de contextos relevantes y estimular las discusiones sobre la naturaleza de la adopción inicial de la cerámica en los Andes del sur.</p><p><br /><strong>Abstract</strong></p><p><br />The earliest pottery marks a milestone in the human history of the southern Andes. This paper proposes an approximation of the date of the earliest pottery using Bayesian chronological models. Models of 84 radiocarbon and thermoluminescence dates from 49 sites are compared among five areas in Argentina (the provinces of San Juan and Mendoza) and Chile (the semi-arid north, central, and south central). Although there are still few data, they show an intriguing pattern of very similar dates with medians between 2100–2180 cal BP (2250–1920, 68% probability, starting boundaries) in four of the areas, though some error ranges are large. The similarity of the dates is striking considering that the macro-region extends over one thousand kilometers (north–south) from 30° to 39°S and includes a diverse range of environments. The contemporaneity is even more notable because these areas include the continent’s southern limit of agriculture. It is hoped this will encourage researchers to more carefully assess this period when excavating and dating relevant contexts as well as encourage discussions on the nature of the initial adoption of ceramics in the southern Andes.</p>


2010 ◽  
Vol 33 (1) ◽  
pp. 19 ◽  
Author(s):  
Fernando J. Gomez ◽  
Ricardo A. Astini

The La Laja Formation is a key unit regarding the hypothesis of the Argentine Precordillera as a Laurentia-derived allochtonous terrane in the south central Andes. Together with the Cerro Totora Formation it comprises the oldest unit exposed at the base of the Lower Paleozoic carbonate platform of the Precordillera. According to previous work these units record the rifting-drifting history of this terrane exotic to Gondwana. The La Laja Formation contrasts with the rest of the overlying units of the Cambro-Ordovician carbonate platform by being partly mixed carbonate-siliciclastic. A detailed facies analysis of the five recognized members in the reference section at Quebrada La Laja (Sierra Chica de Zonda, San Juan Province) allow the recognition of 19 microfacies grouped into four main environmentally significant associations: 1) a storm-influenced, deep subtidal environment with variable influx of fine siliciclastic sediments; 2) shallow subtidal, 3) mixed shallow subtidal and 4) shallow subtidal to intertidal occasionally with well developed high-frequency tidal flat cycles. No deeper basinal or slope facies were found. In contrast, the unit largely records shallow-marine facies with some evidence of subaerial exposure. Medium to coarse, calcareous, feldspar-rich sandstones and sandy limestones characterize the El Estero Member. The base of the Soldano Member shows profuse development of cyclicity with capping oolitic shoals. This member and the upper Juan Pobre Member contain deeper subtidal intervals, below the storm weather wave base, with high percentages of fine terrigenous material represented by shaly marls and nodular limestones. Skeletal-rich and oolite-rich storm beds are recorded within them. Relative shallowing to subaerial environments recorded within the Rivadavia and Las Torres members, with the development of ribbon limestones, intraclastic rudstones, microkarstic surfaces and exposure breccias. Herringbone cross-bedded oolite shoals are common at the top of the uppermost Las Torres Member. The transition into the overlying Zonda Formation is represented by an abrupt rearrangement of the depositional systems and development of meter-scale microbial-rich peritidal cycles. Several orders of superposed cyclicity are recorded within the La Laja Formation. Larger-scale cycles ('Grand Cycles') are inferred from alternating members with important amounts of siliciclastics, whereas meter-scale cycles indicate higher frequency superposed mechanisms. Altogether these show a complex depositional history linking environmental and tectono-eustatic signatures.


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