The Origin of the Geodes of the Keokuk Beds

The presence of great numbers of geodes of varying size and degree of development in the Keokuk beds of the Central Mississippi Valley has long been known to geologists, but their origin has been, from the earliest times, a disputed question, and, although there has been considerable speculation upon the subject, no theory of their formation has been, as yet, widely held

The Lithogenesis of the Sediments

There are few lines of investigation in geology which promise more fruitful returns than the lithogenesis of the sediments. The sedimentary rocks have from the first been sadly neglected although the igneous and metamorphic groups have been systematically and more or less intensively studied both in the field and in the laboratory. Even the megascopic characters of the sediments have for the most part been indefinitely and vaguely described and petrographic examinations have until recently rarely been made. Descriptive terms have been indiscriminately used and such important features as mud cracks and many others equally as significant have in many cases been wholly overlooked. Moreover, until within the last ten years few serious attempts were made to determine the conditions of deposition of the clastic sediments. It is little wonder then that the application of more refined methods of study to these rocks bids fair to revolutionize the fields of physical stratigraphy and paleogeography

Pinnacle features at the base of isolated carbonate buildups marking point sources of fluid offshore Northwest Australia

We investigated pinnacle features at the base of late Oligocene–Miocene isolated carbonate buildups using three-dimensional seismic and borehole data from the Browse Basin, Northwest Australia. Brightened seismic reflections, dim spots, and other evidence of fluid accumulation occur below most pinnacle features. An important observation is that all pinnacles generated topography on successive late Oligocene–Miocene paleoseafloors, therefore forming preferential zones for the settlement of reef-building organisms by raising the paleo-seafloor into the photic zone. Their height ranges from 31 m to 174 m, for a volume varying from 33 km3 to 11,105 km3. Most of the pinnacles, however, are less than 2000 km3 in volume and present heights of 61–80 m. As a result of this work, pinnacles are explained as the first patch reefs formed in association with mud volcanoes or methanogenic carbonates, and they are considered as precluding the growth of the larger isolated carbonate buildups. We postulate that pinnacle features above fluidflow conduits demonstrate a valid seep-reef relationship, and we propose them to be refined diagnostic features for understanding fluid flow through geological time

A Study of the Cherst of the Osage Series of the Mississippian System

The presence of a considerable amount of chert in the Burlington and Keokuk limestone members of the Osage series has been the cause of frequent comment, but no critical study of the material has ever been made. The chert attains its maximum development in the upper division of the Burlington limestone known as the Montrose chert. But nodules and inconstant seams of the same material appear, also, in the lower levels of the Burlington and frequently characterize the Keokuk limestone. In the latter formation, however, the chert is found at no definite level and is entirely wanting at some localities. The present investigation was confined mainly to a study of the Montrose chert, although some attention was given to the chert from other horizons

The Salem Limestone and Its Stratigraphic Relation in Southeastern Iowa

While making a study of the Keokuk beds in southeastern Iowa during the field season of 1911, the writer was attracted by certain irregularities at the contact of those beds with the overlying strata. The Keokuk, instead of being followed always by the Warsaw, which is the normal order, was found to be succeeded above sometimes by a dense, white, fine-grained, non-fossiliferous limestone, and sometimes by a fossiliferous magnesian limestone or by an arenaceous phase into which it grades laterally

The Western Interior Geosyncline and Its Bearing on the Origin and Distribution of the Coal Measures

Late studies of the Mississippian formations of southeastern Iowa for the Iowa Geological Survey have shown that these formations were tilted to the southwestward and partly truncated in late Mississippian time. There is convincing evidence that this tilting was related to deformation over a wide area in southern Iowa, southeastern Nebraska, eastern Kansas and north western Missouri which outlined a southwestwardly pitching geosyncline in which the Coal Measures of the Western Interior coal field were deposited. This geosyncline was shallow in early Pennsylvanian time and probably did not greatly exceed 700 feet in depth at the close of the Cherokee stage. At the present time, however, it is approximately 2400 feet deep at the deepest known point which is at McFarland, Kansas. An important part of the deepening is believed to have been brought about by subsidence during the post-Cherokee stages of the Pennsylvanian

Relevance of unilateral and bilateral sexual polyploidization in relation to intergenomic recombination and introgression in Lilium species hybrids

Sexual polyploids were induced in diploid (2n = 2x = 24) interspecific F1 hybrids of Longiflorum × Asiatic (LA) and Oriental × Asiatic (OA) Lilium hybrids by backcrossing to Asiatic (AA) parents as well as by sib-mating of the F1 LA hybrids. A majority of the BC1 progenies were triploid and the progenies from sib-mating were tetraploid or near tetraploids. Genomic in situ hybridization (GISH) technique was applied to assess the intergenomic recombination in the BC1 populations of LA and OA hybrids obtained after unilateral sexual polyploidization. A total of 63 LA (LA × AA and AA × LA) and 53 OA hybrids were analysed. LA hybrids were originated through the functioning of 2n gametes either as 2n eggs or 2n pollen while those of OA hybrids originated through functional 2n pollen of diploid OA genotype. In both type of crosses, a majority of the progenies had originated through First Division Restitution (FDR) mechanism of functional 2n gamete either with or without a cross over. However, there were nine LA- and four OA-genotypes where Indeterminate Meiotic Restitution (IMR) was the mechanism of 2n gamete formation. Based on GISH, total amount of introgression of Longiflorum and Oriental genome into Asiatic genome was determined. Most of the BC progenies exhibited recombination and the amount of recombination was higher in LA hybrids as compared to OA hybrids. Intergenomic recombination was also determined cytologically in the 16 plants of sib-mated LA hybrids where both parents had contributed 2n gametes. Based on these results the nature of interspecific lily hybrids obtained from uni- and bilateral sexual polyploidization leading to allotriploid and allotetraploid formation is discussed in the context of introgression and intergenomic recombinatio

Hilbert functions of schemes of double and reduced points

It remains an open problem to classify the Hilbert functions of double points in P2. Given a valid Hilbert function Hof a zero-dimensional scheme in P2, we show how to construct a set of fat points Z⊆P2of double and reduced points such that HZ, the Hilbert function of Z, is the same as H. In other words, we show that any valid Hilbert function Hof a zero-dimensional scheme is the Hilbert function of a set a positive number of double points and some reduced points. Fo r some families of valid Hilbert functions, we are also able to show that His the Hilbert function of only double points. In addition, we give necessary and sufficient conditions for the Hilbert function of a scheme of a double points, or double points plus one additional reduced point, to be the Hilbert function of points with support on a star configuration of lines

The Ste. Genevieve Formation and Its Stratigraphic Relations in Southeastern Iowa

In his report on the geology of Lee county Keyes described a fine-grained, compact limestone at the top of the St. Louis formation, resembling lithographic stone in texture. Gordon reported a similar limestone characterized by Spirifer littoni (=Spirifer pellaensis Weller) and Pugnax ottumwa at the same horizon in Van Buren County. Bain subsequently recognized this member in Keokuk County and named it the Pella because of its typical development at the town of this name in the neighboring county of Marion. This name has been adopted by Savage in his geology of Henry County and by Miller in the Marion county report

SNP markers retrieval for a non-model species: a practical approach

<p>Abstract</p> <p>Background</p> <p>SNP (Single Nucleotide Polymorphism) markers are rapidly becoming the markers of choice for applications in breeding because of next generation sequencing technology developments. For SNP development by NGS technologies, correct assembly of the huge amounts of sequence data generated is essential. Little is known about assembler's performance, especially when dealing with highly heterogeneous species that show a high genome complexity and what the possible consequences are of differences in assemblies on SNP retrieval. This study tested two assemblers (CAP3 and CLC) on 454 data from four lily genotypes and compared results with respect to SNP retrieval.</p> <p>Results</p> <p>CAP3 assembly resulted in higher numbers of contigs, lower numbers of reads per contig, and shorter average read lengths compared to CLC. Blast comparisons showed that CAP3 contigs were highly redundant. Contrastingly, CLC in rare cases combined paralogs in one contig. Redundant and chimeric contigs may lead to erroneous SNPs. Filtering for redundancy can be done by blasting selected SNP markers to the contigs and discarding all the SNP markers that show more than one blast hit. Results on chimeric contigs showed that only four out of 2,421 SNP markers were selected from chimeric contigs.</p> <p>Conclusion</p> <p>In practice, CLC performs better in assembling highly heterogeneous genome sequences compared to CAP3, and consequently SNP retrieval is more efficient. Additionally a simple flow scheme is suggested for SNP marker retrieval that can be valid for all non-model species.</p