Dating of the Valsequillo volcanic deposits: Resolution of an ongoing archaeological controversy in Central Mexico

Mark, Darren F.; González, Silvia; Huddart, David; Böhnel, Harald

doi:10.1016/j.jhevol.2010.02.009

Cited by 18 publications

(8 citation statements)

References 15 publications

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“…Placing these deposits into a chronological sequence has been hampered by limited dating control. However, the Xalnene Ash marker is evident in sections throughout the basin and recent work (Renne et al ., ; Mark et al ., ) assigns this tephra to the period around 1.3 Ma and provides a robust geochronological marker for the sequences investigated in our study.…”

Section: Introductionmentioning

confidence: 80%

Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment

Metcalfe¹,

Leng

Kirby³

et al. 2016

J Quaternary Science

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The Valsequillo Basin in Central Mexico has been of interest due to the presence of megafaunal remains and evidence for early human occupation, but research has been controversial. It has been suggested that extensive and deep lakes characterized the Early Pleistocene environment but sediment exposure is highly fragmentary and reliable dating has been difficult. Here we report, for the first time, Early Pleistocene palaeoenvironmental reconstructions using stable isotopes, diatoms, tephra and pollen. We studied several stratigraphic sections of mainly non-volcanic rocks, containing the 1.3-Ma Xalnene Ash as a stratigraphic marker. The isotope and other proxy data show that topographically low points in the basin were occupied by spring-fed, shallow water lakes during the Early-Mid Pleistocene, with a trend to drier conditions. The basin was a dynamic volcaniclastic environment during this period, with the production of the Toluquilla volcanic sequence and other rhyolitic-dacitic volcanic ashes interbedded with the lake sediments at the sections studied. There is no evidence from the sections for extensive and deep lakes before or after deposition of the Xalnene Ash. Wetter conditions in the basin during the Early Pleistocene would have made it attractive for megafauna.

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Section: Introductionmentioning

confidence: 80%

Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment

Metcalfe¹,

Leng

Kirby³

et al. 2016

J Quaternary Science

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“…All Ar isotope data were corrected for backgrounds, mass discrimination and reactor-produced nuclides, and were processed using standard data reduction protocols (e.g. Mark et al 2010aMark et al ,b, 2011a and reported according to the criteria of Renne et al (2009). The atmospheric argon isotope ratios of Lee et al (2006), which have been independently verified by Mark et al (2011b), were employed.…”

Section: Fluid Inclusion Analysismentioning

confidence: 99%

Petroleum generation and migration in the Cambro-Ordovician Laurentian margin succession of NW Scotland

Parnell

Bowden

Mark

2017

JGS

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“…Specifically, we dated a shear with coexisting sericite and molybdenite and a shear containing sericite only from the Sheep Dip vein, and molybdenite and sericite from separate shears cutting vein (106-16). Muscovite within three wall-rock clasts hosted by two different gold-bearing veins (DAL 49 and DAL 6) were targeted for in situ UVLAMP (e.g., Mark et al, 2010b) 40 Ar/ 39 Ar dating (Fig. 15).…”

Section: Samples For Radioisotopic Datingmentioning

confidence: 99%

“…The Re and Os fractions were analyzed for their isotope compositions using negative Thermal ionization mass spectrometry (N-TIMS, Creaser et al, 1991;Volkening et al, 1991) 40 Ar/ 39 Ar dating were prepared as doubly polished fluid inclusion wafers using the evolved approaches of Mark et al (2005Mark et al ( , 2006Mark et al ( , 2008. Sericite for incremental step-heating was prepared using the methodology outlined in Mark et al (2010b). Briefly, samples were crushed gently in a mortar and pestle and subjected to magnetic separation.…”

Section: Re-os Datingmentioning

confidence: 99%

Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland: Implications for Genesis and Classification

et al. 2016

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The Caledonian orogenic belt of northern Britain hosts some significant quartz vein-hosted gold deposits. However, as in orogenic belts worldwide, the relationship between gold mineralization and regional tectonics, magmatism, and metamorphism is a matter of debate. This is primarily due to the absence of precise temporal constraints for the mineralization. Here we report high-precision 40 Ar/ 39 Ar and Re-Os ages for the largest known gold deposit at Curraghinalt (2.7 Moz) in Northern Ireland and use these ages to constrain the regional geologic setting of the gold mineralization and establish a genetic model. The gold resource is contained in a suite of quartz sulfide veins hosted by Neoproterozoic (Dalradian) metasediments, which have been thrust over an Ordovician island arc (Tyrone Igneous Complex). Previous studies recognized two generations of gold sulfide mineralization and we have identified a third in microshears that cut the veins. In the absence of precise geochronological data, mineralization ages from Ordovician to Carboniferous have been proposed. We have dated muscovite (40 Ar/ 39 Ar) in quartz vein-hosted clasts of Dalradian wall rock to 459.3 ± 3.4 Ma (all 40 Ar/ 39 Ar and Re-Os ages herein are reported at the 2σ confidence level including all sources of uncertainty), an age that we interpret as representing the regional cooling path and which provides a maximum age constraint for all gold mineralization. This is consistent with the quartz veins postdating the end of main-stage deformation in the Grampian event of the Caledonian orogeny (ca. 465 Ma). Molybdenite (Re-Os) and sericite (40 Ar/ 39 Ar) from the newly identified gold-bearing microshears (third generation of gold mineralization) yield indistinguishable Re-Os models and 40 Ar/ 39 Ar ages, with a combined age of 455.8 ± 3.0 Ma. The radioisotope ages and field evidence temporally constrain gold mineralization at Curraghinalt to the lower Late Ordovician. Data show that the gold mineralization was emplaced during the Grampian event of the Caledonian orogeny. The ca. 10 Ma maximum possible mineralization interval (462.7-452.8 Ma) for all three episodes of gold emplacement is postpeak metamorphism and main deformation, coinciding with a period of rapid uplift and extensional tectonics following orogenic collapse. While previous studies have suggested the involvement of magmatic fluids in the deposition of the primary gold resource, the absence of magmatism throughout most of the mineralization interval and the nature of the geologic setting suggest that crustal orogenic fluids should also be considered. Overall Curraghinalt displays most of the characteristics of orogenic gold deposits but also some important differences, which may be explained by the geologic setting. The timing of mineralization at Curraghinalt broadly coincides with the shift from compressional to extensional tectonics. The extensional regime, rapid uplift, and a crustal profile comprising metasediments overlying a still hot island arc were ideal for creating large and lo...

show abstract

Dating of the Valsequillo volcanic deposits: Resolution of an ongoing archaeological controversy in Central Mexico

Cited by 18 publications

References 15 publications

Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment

Early–Mid Pleistocene environments in the Valsequillo Basin, Central Mexico: a reassessment

Petroleum generation and migration in the Cambro-Ordovician Laurentian margin succession of NW Scotland

Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland: Implications for Genesis and Classification

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