The eastern Serranía del Interior foreland thrust belt in Venezuela consists of south-vergent thrusts that juxtapose Cretaceous and Paleogene passive margin units with less deformed Neogene basin strata. Apatite fission-track (AFT) ages, mainly from Cretaceous strata, are reset with distinct populations of grain ages that define two different cooling paths (CP). A number of samples have two reset ages that are apparently defined by apatite of different track retentiveness and they therefore record slightly different cooling events. CP1 has significant scatter, but populations of grain ages range from ca. 35–18 Ma, and peak ages decrease from north to south. Previous work estimated a total shortening of 115 km in the Serranía del Interior (Hung, 1997), and a two-stage model for the tectonic evolution of the eastern Serranía del Interior can be inferred. Stage 1 (45–20 Ma) involves in-sequence piggyback folding and imbricate thrusting propagating toward the south. Stage 2 (20–12 Ma) involves envelopment thrusting that doubled the thickness of the thrust sheets. Shortening within the main part of the Serranía del Interior thrust belt ceased at 12 Ma. CP2 is defined by low-retentive apatite. AFT peak ages are southward-younging between 13 and 3 Ma. Cooling ages of these low-retentive grains are only recognized in the northern part of the thrust belt near the El Pilar fault, and therefore these young cooling ages may represent reworking of the thrust belt due to transpression along the plate boundary. Deformation of the Serranía del Interior prior to Eocene and older collision of the Caribbean plate with South America is probably related to the convergence of the North and South American plates, which has been relatively constant since 50 Ma, but has been dominated by dextral transpression since late Miocene.

Fundamental aspects of detrital zircon fission-track analysis in provenance and exhumation studies include etching of fission tracks in zircon, decomposition of grain-age distributions, detection of major bedrock age components, and reproducibility of results. In this study, we present new detrital zircon fission-track data of sediment samples from eight Italian rivers draining the European Alps and previously published data from the Rhône delta in southeastern France. These samples are used to demonstrate that variable etching rates in detrital zircon, which have been shown elsewhere to necessitate a multi-etch procedure during sample preparation, are not a significant problem for zircons from the Alps. Etching response in zircon is a function of radiation damage, principally caused by α-decay. Spontaneous fission-track density can be used as a proxy for total radiation damage. We use spontaneous track density, fission-track cooling age, and uranium content to define a “window of countability” for detrital zircon. We also show that detrital zircon fission-track results are reproducible by comparing results from modern sediments from the same river drainage. The results also compare well with the known distribution of bedrock cooling ages in each drainage area. On a regional scale, our data illustrate that a few samples can provide an overview of the fission-track age pattern of a whole orogen, which is useful for exhumation and provenance studies.