Complex Structure and Stratigraphy of Lower Slices of the Taconic Allochthon Near Middle Granville, New York

The Precambrian (?) to medial Ordovician rocks of the Taconic Allochthon are characterized by argillaceous and arenaceous sediments with lesser associated carbonates, carbonate breccias, and cherts of predominantly deep-water aspect. These allochthonous rocks tectonically overlie an autochthonous to parautochthonous coeval sequence of dominantly shallow marine clastics and carbonates of the Champlain and Vermont Valley sequences. Facies, thickness, sedimentologic, and paleontologic considerations suggest that these coeval sequences represent a carbonate shelf continental rise pair of the east-facing early Paleozoic Atlantic-type margin of North America. This margin formed by the opening of an ocean in latest Precambrian time. The stratigraphy of the shelf suggests that it experienced a complex transgressive-regressive history which is recorded on the rise by marked changes in type of sediment and mode of sedimentation. This Atlantic-type margin was destroyed in the medial Ordovician by eastward subduction and consequent collision beneath the Ammonoosuc volcanic arc. This resulted in the progressive east to west stacking of the rise sequence and subsequent obduction onto the shelf. Obduction involved an exceedingly complex deformation history of folding and imbrication of the shelf, Allochthon and Grenville basement. The stratigraphy of the study area varies considerably across strike. Regions of different, though comparable stratigraphy occur in thrust bonded slices. In the west a stratigraphy closely similar to that defined by Jacobi (1977) is observed. All units, including Bomoseen, Truthville, Browns Pond, Mettawee, Hatch Hill-West Castleton, Poultney, Indian River, Mount Merino, and Pawlet are present. A central region with a similar stratigraphy is recognized, but characterized by less carbonate, thinner and commonly more fine-grained quartzites, which among other aspects suggests that it represents a somewhat more distal (easterly) facies. To the east, the sequence is Bullfrog Hollow Lithozone, Poultney, Indian River (?), Mount Merino (?), and Pawlet. The name Bullfrog Hollow Lithozone is introduced for the basal, apparently thick sequence of purple, green and gray slates and argillites, with associated minor thin quartzites. A thin gray slate with interbedded quartzite and black calcareous quartz wacke lies within the Bullfrog Hollow and is tentatively correlated with the Browns Pond. A new name is used because direct correlations with the Truthville and Mettawee slates of western regions was not possible and other names, such as Bull, St. Catherine, or Mettawee were considered inappropriate because of misuse, poor definition, or the inclusion of untis not observed in this area. Pawlet and Poultney are usually in stratigraphic contact, but locally Indian River and/or Mount Merino are also observed. The Poultney-Pawlet contact appears to be a disconformity. Pawlet and Bullfrog Hollow are locally juxtaposed, but their contact is everywhere interpreted to be structural. Structurally, the study area is quite complex. Four phases of tectonic deformation associated with at least three generations of thrust faults are recognized. Earlier, pre-tectonic, syndepositional deformation features (DO) are also recognized. The earliest tectonic deformation (Dl) is only locally recognizable. It involves macroscopic isoclinal and initially recumbent folds (Fl) and axial surface-parallel thrusts (T1). F1 folds and T1 thrusts are refolded by prominent west-verging, asymmetric, overturned folds (F2) with an axial surface slaty cleavage (S2). Thrusting (T2) parallel or somewhat less steep than F2 axial surfaces imbricates and dismembers the F2 folds. These structures pre-date the Giddings Brook Thrust. Mesoscopic refolding of D2 and earlier structures by F3 folds which are associated with an axial surface crenulation cleavage (S3) is observed, but is not macroscopically significant. A third generation of thrusts (T3) that dip significantly less steeply east than F2 axial surfaces are prominent in this area and may be temporally associated with F3 folds, but this cannot be proven. T3 thrusts may be of the same age as the Giddings Brook Thrust. Rare vertical kink bands (F4) represent the fourth tectonic deformation and are not considered to be significant to the regional structure

Stable isotope‐based paleoaltimetry,

Abstract The quantitative estimation of paleoaltitude has become an increasing focus of Earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts, as well as the influence of mountain belt growth on regional and global climate. The general observation of decreasing δ 18 O and δ 2 H values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation. These studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming. In this review we provide a theory behind the application of stable isotope-based approaches to paleoaltimetry. We apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations. Examples of the application of paleoaltimetry techniques to Himalaya-Tibet and the Andes are discussed with implications for processes that cause surface uplift

A Cretaceous‐Eocene depositional age for the Fenghuoshan Group, Hoh Xil Basin: Implications for the tectonic evolution of the northern Tibet Plateau

The Fenghuoshan Group marks the initiation of terrestrial deposition in the Hoh Xil Basin and preserves the first evidence of uplift above sea level of northern Tibet. The depositional age of the Fenghuoshan Group is debated as are the stratigraphic relationships between the Fenghuoshan Group and other terrestrial sedimentary units in the Hoh Xil Basin. We present new radiometric dates and a compilation of published biostratigraphic data which are used to reinterpret existing magnetostratigraphic data from the Fenghuoshan Group. From these data, we infer an 85–51 Ma depositional age range for the Fenghuoshan Group. U‐Pb detrital zircon age spectra from this unit are compared to age spectra from Tibetan terranes and Mesozoic sedimentary sequences to determine a possible source terrane for Fenghuoshan Group strata. We propose that these strata were sourced from the Qiangtang Terrane and may share a common sediment source with Cretaceous sedimentary rocks in Nima Basin. Field relationships and compiled biostratigraphic data indicate that the Fenghuoshan and Tuotuohe Groups are temporally distinct units. We report late Oligocene ages for undeformed basalt flows that cap tilted Fenghuoshan Group strata. Together, our age constraints and field relationships imply exhumation of the central Qiangtang Terrane from the Late Cretaceous to earliest Eocene, followed by Eocene‐Oligocene deformation, and shortening of the northern Qiangtang and southern Songpan‐Ganzi terranes. Crustal shortening within the Hoh Xil Basin ceased by late Oligocene time as is evident from flat‐lying basaltic rocks, which cap older, deformed strata. Key Points The Fenghuoshan Group was deposited from late Cretaceous to early Eocene time The Fenghuoshan Group was likely sourced from the central Qiangtang Terrane Crustal shortening of the Hoh Xil Basin occurred from Eocene to Oligocene timePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/1/ts02.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/2/fs02.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/3/tect20113.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/4/ts06.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/5/fs06.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/6/ts03.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/7/fs03.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/8/ts07.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/9/fs07.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/10/fs04.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/11/ts04.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/12/fs01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/13/ts08.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/14/ts01.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/15/fs05.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106814/16/ts05.pd

Kinematics and dynamics of the east pacific rise linked to a stable, deep-mantle upwelling

Earth’s tectonic plates are generally considered to be driven largely by negative buoyancy associated with subduction of oceanic lithosphere. In this context, mid-ocean ridges (MORs) are passive plate boundaries whose divergence accommodates flow driven by subduction of oceanic slabs at trenches. We show that over the past 80 million years (My), the East Pacific Rise (EPR), Earth’s dominant MOR, has been characterized by limited ridge-perpendicular migration and persistent, asymmetric ridge accretion that are anomalous relative to other MORs. We reconstruct the subduction-related buoyancy fluxes of plates on either side of the EPR. The general expectation is that greater slab pull should correlate with faster plate motion and faster spreading at the EPR. Moreover, asymmetry in slab pull on either side of the EPR should correlate with either ridge migration or enhanced plate velocity in the direction of greater slab pull. Based on our analysis, none of the expected correlations are evident. This implies that other forces significantly contribute to EPR behavior. We explain these observations using mantle flow calculations based on globally integrated buoyancy distributions that require core-mantle boundary heat flux of up to 20 TW. The time-dependent mantle flow predictions yield a long-lived deep-seated upwelling that has its highest radial velocity under the EPR and is inferred to control its observed kinematics. The mantle-wide upwelling beneath the EPR drives horizontal components of asthenospheric flows beneath the plates that are similarly asymmetric but faster than the overlying surface plates, thereby contributing to plate motions through viscous tractions in the Pacific region

Seafloor Spreading, Sea Level, and Ocean Chemistry Changes

High Cretaceous ocean crust production rates have been causally linked to high global sea level and global CO_2 due to increased outgassing. However, recent studies have questioned the empirical basis for high Cretaceous global seafloor spreading rates, high Cretaceous sea level (230-320 m above present), and the relationship between geochemical fluxes and spreading rates. Although this topic has been discussed at several recent international meetings, there has been little opportunity for the protagonists in the debate of constant versus variable global seafloor spreading rates to interact. However, a group of tectonophysicists, stratigraphers, and geochemists recently met at Rutgers, The State University of New Jersey (Piscataway N.J.) to discuss global seafloor spreading changes and their possible relationships to sea level and geochemical variations

lxodes dammini (Acari, Ixodidae) and Borrelia burgdorferi in Iowa

A statewide study to evaluate the presence, distribution and abundance of the deer tick, Ixodes dammini, and the spirochete, Borrelia burgdorfen, in Iowa was initiated in 1989. Six hundred and seventy-one tick collections were received from health professionals, conservation employees and concerned citizens. Additional ticks were obtained by flagging, small mammal trapping and deer checks in selected areas of Iowa. Nine I. dammini were collected in 1989 from seven counties in the eastern half of the state. Six of these were tested for B. burgdorferi and all were negative. Flagging, small mammal trapping and deer checks in eastern Iowa failed to produce I. dammini in 1989. However, in May 1990 and dammini female collected by a turkey hunter in Allamakee Co. tested positive for B. burgdoiferi. Subsequent flagging in this area yielded I. dammini adults, 19% of which were infected. Additionally, I. dammini larvae and nymphs were collected from Peromyscus leucopus. This is the first evidence of I. dammini establishment and B. burgdoiferi presence in Iowa

Self-similar scaling and evolution in the galaxy cluster X-ray Luminosity-Temperature relation

We investigate the form and evolution of the X-ray luminosity-temperature (LT) relation of a sample of 114 galaxy clusters observed with Chandra at 0.1<z<1.3. The clusters were divided into subsamples based on their X-ray morphology or whether they host strong cool cores. We find that when the core regions are excluded, the most relaxed clusters (or those with the strongest cool cores) follow an LT relation with a slope that agrees well with simple self-similar expectations. This is supported by an analysis of the gas density profiles of the systems, which shows self-similar behaviour of the gas profiles of the relaxed clusters outside the core regions. By comparing our data with clusters in the REXCESS sample, which extends to lower masses, we find evidence that the self-similar behaviour of even the most relaxed clusters breaks at around 3.5keV. By contrast, the LT slopes of the subsamples of unrelaxed systems (or those without strong cool cores) are significantly steeper than the self-similar model, with lower mass systems appearing less luminous and higher mass systems appearing more luminous than the self-similar relation. We argue that these results are consistent with a model of non-gravitational energy input in clusters that combines central heating with entropy enhancements from merger shocks. Such enhancements could extend the impact of central energy input to larger radii in unrelaxed clusters, as suggested by our data. We also examine the evolution of the LT relation, and find that while the data appear inconsistent with simple self-similar evolution, the differences can be plausibly explained by selection bias, and thus we find no reason to rule out self-similar evolution. We show that the fraction of cool core clusters in our (non-representative) sample decreases at z>0.5 and discuss the effect of this on measurements of the evolution in the LT relation.Comment: 21 pages, 15 figures. Submitted to MNRAS. Comments welcom

The genetic architecture of breast papillary lesions as a predictor of progression to carcinoma

Intra-ductal papillomas (IDP) are challenging breast findings because of their variable risk of progression to malignancy. The molecular events driving IDP development and genomic features of malignant progression are poorly understood. In this study, genome-wide CNA and/or targeted mutation analysis was performed on 44 cases of IDP, of which 20 cases had co-existing ductal carcinoma in situ (DCIS), papillary DCIS or invasive ductal carcinoma (IDC). CNA were rare in pure IDP, but 69% carried an activating PIK3CA mutation. Among the synchronous IDP cases, 55% (11/20) were clonally related to the synchronous DCIS and/ or IDC, only one of which had papillary histology. In contrast to pure IDP, PIK3CA mutations were absent from clonal cases. CNAs in any of chromosomes 1, 16 or 11 were significantly enriched in clonal IDP lesions compared to pure and non-clonal IDP. The observation that 55% of IDP are clonal to DCIS/IDC indicates that IDP can be a direct precursor for breast carcinoma, not limited to the papillary type. The absence of PIK3CA mutations and presence of CNAs in IDP could be used clinically to identify patients at high risk of progression to carcinoma

CRUZ, MARUJA [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201