Evidence for the ~ 1.4 Ga Picuris orogeny in the central Colorado Front Range

We present the first evidence for sedimentation and new evidence for penetrative deformation and metamorphism in the central Colorado Front Range associated with the ~ 1.48–1.35 Ga Picuris orogeny. This orogeny has recently been recognized in New Mexico, Arizona and southern Colorado and may be part of a larger active accretionary margin that includes the ~ 1.51–1.46 Ga Pinware and Baraboo events, in eastern Canada and central US respectively, that preceded the amalgamation of the Rodinian supercontinent. We demonstrate that in addition to ~ 1.4 Ga reactivation of northeast-trending Paleoproterozoic shear zones, regional folding occurred in an area south of Mt. Evans, away from these shear zones. Detrital zircon from one quartzite yielded U–Pb laser ablation inductively coupled mass spectrometry (LAICPMS) major age populations of ~ 1.81–1.61 Ga and ~ 1.49–1.38 Ga, and minor ones of ~ 1.90 Ga and ~ 1.56 Ga. The Paleoproterozoic and ~ 1.49–1.38 Ga populations have numerous local and regional sources. The ~ 1.56 Ga age population may represent a minor exotic population as recognized in Defiance, Arizona the Yankee Joe and Blackjack Formations in Arizona, the Four Peaks area in Arizona, and the Tusas and Picuris Mountains in New Mexico. Alternatively it may be a result of mixing between zircon age domains reflecting the older and younger populations, or Pb loss from 1.81 to 1.61 Ga zircon. In-situ LA-ICPMS U–Pb analysis on monazite from four biotite schist samples yielded ~ 1.74 Ga and ~ 1.42 Ga age populations, and separate populations that show ~ 1.68–1.47 Ga and ~ 1.39–1.33 Ga age spreads. The ~ 1.74 Ga and ~ 1.68–1.47 Ga populations may be detrital or metamorphic. Monazite ages between ~ 1.6 Ga and ~ 1.5 Ga may be due to the mixing of age domains or Pb loss, because metamorphism during that time has not been recognized in Laurentia. The ~ 1.42 Ga and ~ 1.39–1.33 Ga populations are most likely metamorphic and consistent with the age of the ~ 1.48–1.35 Ga Picuris orogeny. The evidence for ~ 1.4 Ga sedimentation, and especially regional folding and metamorphism in the central Colorado Front Range indicate that the impact and extent of the Picuris orogeny in the southwestern U.S. are larger than previously thought

On the occurrence of amphibolite-facies sapphirine, spinel, phlogopite, anorthite, and corundum in the Wet Mountains, Colorado, USA

The Wet Mountains, southern Colorado, expose Mesoproterozoic metamorphic and magmatic rocks that record the early deformational history of the west–central continental USA and growth of Laurentia. Of particular petrological interest are halogen-enriched metamorphic rocks adjacent to the San Isabel A-type granite, situated in the southern Wet Mountains, which contain sapphirine, spinel, phlogopite, anorthite, and corundum. Conventional thermobarometry and phase diagram-based thermodynamic modeling indicates peak pressure–temperature (P–T) conditions of metamorphism within the upper amphibolite facies (∼750–770 °C) at middle-crustal pressures (∼6–7 kbar), and in-situ U-Pb geochronology of monazite constrains peak metamorphism to c. 1340–1320 Ma. These sapphirine-hornfels units are younger than metamorphic lithologies elsewhere in the southern Wet Mountains (c. 1430 Ma), but only slightly post-date the timing of intrusion of the granite itself (1362 ± 7 Ma). These rocks are thus interpreted to be of contact metamorphic origin, with high F contents in mica and amphibole interpreted to record metasomatism in the middle crust by halogen-rich fluids expelled by the San Isabel granite. However, as the temperature of emplacement and crystallization of the granite likely did not greatly exceed 800–850 °C, these rocks document an unusual occurrence of normally granulite-facies and (ultra)high-temperature metamorphic minerals stabilizing at lower grade. Thus, caution must be used when using such parageneses as field indicators of geodynamic settings associated with extreme heat flow, such as continental rifting and/or voluminous emplacement of dry, mafic magma

Detrital Zircon Record of Magmatism and Sediment Dispersal Across the North American Cordilleran Arc System (28–48°N)

As zircon U-Pb geochronology has become a leading method in sediment provenance studies and basin analysis over the past 20 years, the volume of detrital zircon data made available in published literature has enabled researchers to go beyond source-to-sink provenance studies to explore increasingly complex geologic problems. In this review, we utilize the growing body of detrital zircon data acquired from Jurassic-Paleocene forearc and foreland basin strata of the North American Cordillera to investigate the Mesozoic to earliest Cenozoic evolution of the arc and its associated basins between 28°N and 48°N. Our compilation includes 830 detrital zircon samples (101,898 individual ages) from 70 studies published between 2000 and 2020. For comparative purposes, we also compile 1307 igneous zircon U-Pb ages that characterize the magmatic history of the arc. We place primary emphasis on detrital zircon ages between 251 and 56 Ma that we infer to be uniquely derived from magmatic sources in the arc. Informed by existing knowledge of magmatic, structural, and sedimentological processes that acted on the orogen, we investigate spatial and temporal trends in these “arc-derived zircon” to establish a detrital record of arc magmatism, investigate source-to-sink relationships between the arc and adjacent basins, and discuss controls on sediment dispersal across the orogen. Our review shows that compilations of detrital zircon data from the Cordilleran forearc and foreland basin systems are excellent proxies for arc magmatism because the basins are enriched in arc-derived zircon and compilations provide space- and time-integrated records of crystallization ages. The compiled detrital zircon data support a history of continuous arc magmatism throughout Mesozoic and earliest Cenozoic time, characterized by low-volume magmatism from Triassic-Early Jurassic time (~251–174 Ma) and episodic higher-volume magmatism from Middle Jurassic-Late Cretaceous time (~174–66 Ma). These trends elucidate the initiation and timing of magmatic events at the orogen-scale and corroborate our understanding of cyclic arc behavior. Detrital zircon distributions are spatially and temporally variable both within and across basins, which we discuss relative to topographic development of the orogen and attendant responses of sediment dispersal systems. Detrital zircon distributions in the forearc signal rapid transfer of sediment from the arc to basins dominantly via fluvial processes. In contrast, detrital zircon distributions across the foreland reflect the presence of topographic barriers in the hinterland region of the arc that effectively isolated parts of the foreland. The presence of hinterland topography in turn highlights the important role of ash-fall events in delivering arc-derived zircon to the foreland, underscoring the need to consider ash-fall processes in paleodrainage reconstructions. These broad regional trends, and in general the close linkage between orogenic process and sediment dispersal, emerge from our compilation because it averages out much of the local variability observed in studies of more limited geographic or temporal extent

A Stratigraphic Approach to Inferring Depositional Ages From Detrital Geochronology Data

With the increasing use of detrital geochronology data for provenance analyses, we have also developed new constraints on the age of otherwise undateable sedimentary deposits. Because a deposit can be no older than its youngest mineral constituent, the youngest defensible detrital mineral age defines the maximum depositional age of the sampled bed. Defining the youngest “defensible” age in the face of uncertainty (e.g., analytical and geological uncertainty, or sample contamination) is challenging. The current standard practice of finding multiple detrital minerals with indistinguishable ages provides confidence that a given age is not an artifact; however, we show how requiring this overlap reduces the probability of identifying the true youngest component age. Barring unusual complications, the principle of superposition dictates that sedimentary deposits must get younger upsection. This fundamental constraint can be incorporated into the analysis of depositional ages in sedimentary sections through the use of Bayesian statistics, allowing for the inference of bounded estimates of true depositional ages and uncertainties from detrital geochronology so long as some minimum age constraints are present. We present two approaches for constructing a Bayesian model of deposit ages, first solving directly for the ages of deposits with the prior constraint that the ages of units must obey stratigraphic ordering, and second describing the evolution of ages with a curve that represents the sediment accumulation rate. Using synthetic examples we highlight how this method preforms in less-than-ideal circumstances. In an example from the Magallanes Basin of Patagonia, we demonstrate how introducing other age information from the stratigraphic section (e.g., fossil assemblages or radiometric dates) and formalizing the stratigraphic context of samples provides additional constraints on and information regarding depositional ages or derived quantities (e.g., sediment accumulation rates) compared to isolated analysis of individual samples

A geochronological review of magmatism along the external margin of Columbia and in the Grenville-age orogens forming the core of Rodinia

A total of 4344 magmatic U-Pb ages in the range 2300 to 800 Ma have been compiled from the Great Proterozoic Accretionary Orogen along the margin of the Columbia / Nuna supercontinent and from the subsequent Grenvillian collisional orogens forming the core of Rodinia. The age data are derived from Laurentia (North America and Greenland, n = 1212), Baltica (NE Europe, n = 1922), Amazonia (central South America, n = 625), Kalahari (southern Africa and Dronning Maud Land in East Antarctica, n = 386), and western Australia (n = 199). Laurentia, Baltica, and Amazonia (and possibly other cratons) most likely formed a ca. 10 000-km-long external active continental margin of Columbia from its assembly at ca. 1800 Ma until its dispersal at ca. 1260 Ma, after which all cratons studied were involved in the Rodinia-forming Grenvillian orogeny. However, the magmatic record is not smooth and even but highly irregular, with marked peaks and troughs, both for individual cratons and the combined data set. Magmatic peaks typically range in duration from a few tens of million years up to around hundred million years, with intervening troughs of comparable length. Some magmatic peaks are observed on multiple cratons, either by coincidence or because of paleogeographic proximity and common tectonic setting, while others are not. The best overall correlation, 0.617, is observed between Baltica and Amazonia, consistent with (but not definitive proof of) their being close neighbours in a SAMBA-like configuration at least in Columbia, and perhaps having shared the same peri-Columbian subduction system for a considerable time. Correlation factors between Laurentia and Baltica, or Laurentia and Amazonia, are below 0.14. Comparison between the Grenville Province in northeastern Laurentia and the Sveconorwegian Province in southwestern Fennoscandia (Baltica) shows some striking similarities, especially in the Mesoproterozoic, but also exhibits differences in the timing of events, especially during the final Grenville-Sveconorwegian collision, when the Sveconorwegian evolution seems to lag behind by some tens of million years. Between the other cratons, the evolution before and during the final Grenvillian collision is also largely diachronous. After 900 Ma, magmatic activity had ceased in all areas investigated, attesting to the position of most of them within the stable interior of Rodinia.publishedVersio

Change in diet, physical activity, and body weight among young-adults during the transition from high school to college

<p>Abstract</p> <p>Background</p> <p>The freshmen year of college is likely a critical period for risk of weight gain among young-adults.</p> <p>Methods</p> <p>A longitudinal observational study was conducted to examine changes in weight, dietary intake, and other health-related behaviors among first-year college students (n = 186) attending a public University in the western United States. Weight was measured at the beginning and end of fall semester (August – December 2005). Participants completed surveys about dietary intake, physical activity and other health-related behaviors during the last six months of high school (January – June 2005) in August 2005 and during their first semester of college (August – December 2005) in December 2005.</p> <p>Results</p> <p>159 students (n = 102 women, 57 men) completed both assessments. The average BMI at the baseline assessment was 23.0 (standard deviation (SD) 3.8). Although the average amount of weight gained during the 15-week study was modest (1.5 kg), 23% of participants gained ≥ 5% of their baseline body weight. Average weight gain among those who gained ≥ 5% of baseline body weight was 4.5 kg. Those who gained ≥ 5% of body weight reported less physical activity during college than high school, were more likely to eat breakfast, and slept more than were those who did not gain ≥ 5% of body weight.</p> <p>Conclusion</p> <p>Almost one quarter of students gained a significant amount of weight during their first semester of college. This research provides further support for the implementation of education or other strategies aimed at helping young-adults entering college to achieve or maintain a healthy body weight.</p

The Freshman 15: A Critical Time for Obesity Intervention or Media Myth?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88020/1/ssqu823.pd

Characteristics of Suicide Attempts in Anorexia and Bulimia Nervosa: A Case–Control Study

Objective: Compared to other eating disorders, anorexia nervosa (AN) has the highest rates of completed suicide whereas suicide attempt rates are similar or lower than in bulimia nervosa (BN). Attempted suicide is a key predictor of suicide, thus this mismatch is intriguing. We sought to explore whether the clinical characteristics of suicidal acts differ between suicide attempters with AN, BN or without an eating disorders (ED). Method: Case-control study in a cohort of suicide attempters (n = 1563). Forty-four patients with AN and 71 with BN were compared with 235 non-ED attempters matched for sex, age and education, using interview measures of suicidal intent and severity. Results: AN patients were more likely to have made a serious attempt (OR = 3.4, 95 % CI 1.4–7.9), with a higher expectation of dying (OR = 3.7,95 % CI 1.1–13.5), and an increased risk of severity (OR = 3.4,95 % CI 1.2–9.6). BN patients did not differ from the control group. Clinical markers of the severity of ED were associated with the seriousness of the attempt. Conclusion: There are distinct features of suicide attempts in AN. This may explain the higher suicide rates in AN. Higher completed suicide rates in AN may be partially explained by AN patients ’ higher desire to die and their more severe and lethal attempts

Eating disordered behaviours in portuguese athletes: the influence of personal, sport, and psychological variables

Objective: This study describes eating disordered behaviours in a sample of Portuguese elite athletes and analyses the impact of personal and sports factors on those eating disordered behaviours. Method: Two hundred and ninety athletes (51.7% males) practicing collective (64.8%) and individual sports have been included. The evaluation protocol included the Eating Disorder Examination Questionnaire; the Sport Condition Questionnaire; the Sport Anxiety Scale; the Task and Ego Orientation in Sport Questionnaire; the Cognitive Evaluation of Sport–Threat Perceptions; and the Self-Presentation Exercise Questionnaire. Results: Females, athletes with a higher body mass index, and those with a desire to weigh less, reported more eating disordered behaviours. No relation with sports variables was found. Finally, a higher prevalence of eating disorders behaviour was predicted by lower satisfaction in terms of body shape and physical appearance, higher anxiety and impression motivation. Conclusion: Personal characteristics of athletes, as well as their body satisfaction, anxiety, impression motivation and threat perception, and coach comments on their weight, represent dimensions that could raise the risk for eating disorders