Geologic Story of the Lower Wabash Valley with Empahsis on the New Harmony Area

Indiana Geological Survey Occasional Paper 27The lower Wabash Valley--complex physiographic wonder: capricious (or misunderstood?) phenomenon; tireless geologic agent; artery, resource, playground, and home for prehistoric and modern man alike--what are its origins, how does it gain its boundless energy, and of what legacy does its physiography speak

A Real Time Microprocessor Based Digital Filter Implementation

A major break-through in the real-time digital simulation of dynamic models has occurred with the introduction of the Intel 2920 digital signal processing chip. The problems and potentials for this new device are demonstrated by implementing an elliptic function digital low pass filter via the bilinear z-transform approach. The software implementation is presented. Debugging and software verification are accomplished via manufacturer\u27s simulation software tools. The hardware performance is verified in the laboratory. The results of these efforts point to much promise for wide scale applications, however, problems associated with performance indicate early version chip problems

Adventures with Fossils

Indiana Geological Survey Circular 6Many laymen write to the Indiana Geological Survey and ask: “Please send me books and maps on fossils and where they can be found.” Some write on tablet paper in the labored fifth-grade hand of a school child; others write on linen in the neatly feminine and classic lines that are surely those of a school teacher; still others type on expensive letterheads that show the nature of their professions. This circular is written for all of them but especially for those of school age. It is for school teachers, scoutmasters, parents, and other counselors of children. It is a beginner’s guide to fossils, most useful to collectors in Indiana. It is for the curious everywhere who do not write to me, but who seek a hobby, avocation, or beginning knowledge to a profession. It is for all who are interested and seek, through fossils, one means to the Truth.Indiana Department of Conservatio

A Field Guide and Recollections The David Dale Owen Years to the Present

One hundred and fifty years ago marked the beginnings of a remarkable geologic odyssey funded by the State of Indiana. The legislature of this then pioneer state appropriated less and $2,000 annually for David Dale Owen to conduct a geological survey of the state. David Dale Owen accomplished much more than perhaps even the modern state legislature has yet realized

J06587-5558 -- A Very Unusual Polarised Radio Source

We have found a peculiar radio source in the field of one of the hottest known clusters of galaxies 1E0657-56. It is slightly extended, highly polarised (54% at 8.8GHz) and has a very steep spectrum, with alpha ~ -1 at 1.3 GHz, steepening to ~ -1.5 at 8.8GHz (S \propto nu^alpha). No extragalactic sources are known with such high integrated polarisation, and sources with spectra as steep as this are rare. In this paper, we report the unusual properties of the source J06587-5558 and speculate on its origin and optical identification.Comment: 5 pages, 6 figures, accepted by MNRAS letter

The Silurian Formations of Northern Indiana

Indiana Geological Survey Bulletin 32The Silurian rocks in northern Indiana include, in ascending order, the Brassfield Limestone (lower Silurian), the Salamonie Dolomite, the Louisville Limestone, and the Wabash Formation, all of the Niagaran Series (middle Silurian), and the Salina Formation (middle? and upper Silurian). Some of these names are new or newly applied in this area. The oldest exposed Silurian rocks (Brassfield) are found in the southeastern part of the area, and they are highest on the major positive structural feature of the area, which is the northwest extension of the Cincinnati Arch. Generally younger rocks are found exposed northwestward, but the Salina Formation interrupts this pattern and is exposed in two areas centered in Howard and Cass Counties and in Jasper County. A disconformity appears to separate Silurian from older rocks, and the upper part of the Richmond Group (upper Ordovician) possibly is absent from parts of northwestern Indiana. The Ordovician Silurian boundary can be identified readily by conodont faunas, and no variation of the regular order of succession of named lower Silurian units has been observed. Thus there is no evidence favoring the classic idea of a barrier between northern and southern parts of the State. The Brassfield Limestone is 6 to 100 feet thick and consists of mostly noncherty partly glauconitic carbonate rocks. The formation corresponds only to the lower part of what commonly has been called the Brassfield in subsurface studies. As thus restricted, the Brassfield in its different areas is equivalent to part of the Edgewood Limestone and the lower part of the Kankakee Dolomite of northeastern Illinois and the lower part of what has been called the Cataract Formation in northern Indiana and southern Michigan. The Salamonie Dolomite (new name; lower Niagaran) is 95 to 275 feet thick, partly argillaceous and cherty in its lower part, and pure vuggy dolomite in its upper part. This formation is equivalent approximately (1) in its lower and middle parts to the Osgood Formation and the Laurel Limestone through the Cedarville Dolomite of Preble County, Ohio, (3) to most of the Kankakee and Joliet Dolomites of northeastern Illinois, and (4) to some of the so-called Brown Niagaran and White Niagaran rocks and much of the undifferentiated Niagaran rocks of the Michigan Basin. The Waldron Formation (new surname), about 15 feet thick, consists of nodular argillaceous dolomite; the Louisville Limestone, about 60 feet thick, consists variably of argillaceous and fossil fragmental rocks. These formations, of middle Niagaran age, are absent from the area that generally corresponds to the northern two tiers of Indiana counties and where the combined thickness of the underlying Brassfield and Salamonie rocks is greater than 300 feet. In this area the Salina Formation overlies the Salamonie Dolomite. The Waldron and the Louisville correspond to the Waukesha Limestone and possibly to the lower part of the Racine Dolomite of northeastern Illinois. The Wabash Formation (new name; upper Niagaran) is about 150 to more than 200 feet thick and consists of reef-bearing argillaceous and cherty carbonate rocks. It includes the Mississinewa Shale and Liston Creek Limestone Members (new ranks) in their type areas in north- central Indiana. The term Huntington Lithofacies (no status in systematic nomenclature) is given to reef, biohermal, and bank lithologies, and the name Fort Wayne Bank is applied to the basin-fringing accumulation of vuggy biohermal and biostromal dolomites that extend from near Fort Wayne to Lake Michigan. The Wabash Formation terminates northward in its bank phase against the Salina Formation, generally along the southern part of the northern two tiers of Indiana counties. It corresponds mostly to the Racine Dolomite of northeastern Illinois and to the Guelph Dolomite of areas north and east of Indiana. The Salina Formation (Niagaran? and lower Cayugan) consists variably of laminated, shaly, cherty, or pure carbonate rocks. This formation is 500 feet thick in northeastern Indiana but wedges out southwestward in two fingerlike projections that apparently are controlled structurally. These projections lie in the Logansport Sag and in the Jasper Sag (new name), where Salina and Wabash rocks are juxtaposed. The Salina includes the Kokomo and Kenneth Limestone Members (new ranks) and other, unassigned rocks. The Salina Formation in Indiana corresponds mostly to the A unit and partly to higher units of that formation as understood in Michigan. Possibly the Salina in its areas of great thickness in Indiana and in Michigan has partial age equivalence with Wabash rocks and rocks as old as the Waldron, but not necessarily in areas having close proximity.Indiana Department of Conservatio

Probing High Redshift Radiation Fields with Gamma-Ray Absorption

The next generation of gamma-ray telescopes may be able to observe gamma-ray blazars at high redshift, possibly out to the epoch of reionization. The spectrum of such sources should exhibit an absorption edge due to pair-production against UV photons along the line of sight. One expects a sharp drop in the number density of UV photons at the Lyman edge E_{L}. This implies that the universe becomes transparent after gamma-ray photons redshift below E (m_{e}c^2)^{2}/E_{L} 18 GeV. Thus, there is only a limited redshift interval over which GeV photons can pair produce. This implies that any observed absorption will probe radiation fields in the very early universe, regardless of the subsequent star formation history of the universe. Furthermore, measurements of differential absorption between blazars at different redshifts can cleanly isolate the opacity due to UV emissivity at high redshift. An observable absorption edge should be present for most reasonable radiation fields with sufficient energy to reionize the universe. Ly-alpha photons may provide an important component of the pair-production opacity. Observations of a number of blazars at different redshifts will thus allow us to probe the rise in comoving UV emissivity with time.Comment: ApJ accepted version, minor changes. 19 pages, 5 figure

Reionization and the large-scale 21 cm-cosmic microwave background cross correlation

Of the many probes of reionization, the 21 cm line and the cosmic microwave background (CMB) are among the most effective. We examine how the cross-correlation of the 21 cm brightness and the CMB Doppler fluctuations on large angular scales can be used to study this epoch. We employ a new model of the growth of large scale fluctuations of the ionized fraction as reionization proceeds. We take into account the peculiar velocity field of baryons and show that its effect on the cross correlation can be interpreted as a mixing of Fourier modes. We find that the cross-correlation signal is strongly peaked toward the end of reionization and that the sign of the correlation should be positive because of the inhomogeneity inherent to reionization. The signal peaks at degree scales (l~100) and comes almost entirely from large physical scales (k~0.01 Mpc). Since many of the foregrounds and noise that plague low frequency radio observations will not correlate with CMB measurements, the cross correlation might appear to provide a robust diagnostic of the cosmological origin of the 21 cm radiation around the epoch of reionization. Unfortunately, we show that these signals are actually only weakly correlated and that cosmic variance dominates the error budget of any attempted detection. We conclude that the detection of a cross-correlation peak at degree-size angular scales is unlikely even with ideal experiments.Comment: 15 pages, 4 figures, submitted to MNRA

The Sunyaev-Zeldovich Effect at 1 and 2 mm towards ROSAT Clusters

An observing campaign was devoted to the search for the Sunyaev-Zeldovich (S-Z) effect towards X-ray ROSAT Clusters in the millimetric spectral domain. A double channel (1.2 and 2 {\it mm}) photometer was installed at the focus of the 15m Swedish ESO Submillimeter Telescope (SEST) in Chile in september 1994 and 1995 and observations of the targets S1077, A2744, S295 and RXJ0658-5557 were gathered. Detections were found for A2744 at 1 {\it mm} and in both channels (at 1.2 and 2 {\it mm}) towards RXJ0658-5557. For the first time there is evidence for the S-Z enhancement and both the latter and the decrement were detected on the same source. We discuss astrophysical and systematic effects which could give origin to these signals.Comment: 6 pg Latex file (style file included) including 1 ps figure, XVIth Moriond Astrophysics Meeting "The Anisotropies of the Cosmic Microwave Background", Les Arcs, Savoie-France, March 16-23 199

Radio Signatures of HI at High Redshift: Mapping the End of the ``Dark Ages''

The emission of 21-cm radiation from a neutral intergalactic medium (IGM) at high redshift is discussed in connection with the thermal and ionization history of the universe. The physical mechanisms that make such radiation detectable against the cosmic microwave background include Ly_alpha coupling of the hydrogen spin temperature to the kinetic temperature of the gas and preheating of the IGM by the first generation of stars and quasars. Three different signatures are investigated in detail: (a) the fluctuations in the redshifted 21-cm emission induced by the gas density inhomogeneities that develop at early times in cold dark matter (CDM) dominated cosmologies; (b) the sharp absorption feature in the radio sky due to the rapid rise of the Ly_alpha continuum background that marks the birth of the first UV sources in the universe; and (c) the 21-cm emission and absorption shells that are generated on several Mpc scales around the first bright quasars. Future radio observations with projected facilities like the Giant Metrewave Radio Telescope and the Square Kilometer Array may shed light on the power spectrum of density fluctuations at z>5, and map the end of the "dark ages", i.e. the transition from the post-recombination universe to one populated with radiation sources.Comment: LateX, 19 pages, 5 figures, significantly revised version to be published in the Ap