Properties, origin and nomenclature of rodlets of the inertinite maceral group in coals of the central Appalachian basin, U.S.A.

Resin rodlets, sclerenchyma strands and woody splinters, which are collectively called rodlets, were studied by chemical, optical petrographic, and scanning-electron microscopic (SEM) techniques. A study was made of such rodlets from the bituminous coal beds of the central Appalachian basin (Pennsylvanian; Upper Carboniferous) of the United States. Comparisons were made with rodlets from coal beds of the Illinois basin, the Southern Anthracite Field of Pennsylvania, the St. Rose coal field of Nova Scotia, and European and other coal fields. In order to determine their physical and chemical properties, a detailed study was made of the rodlets from the Pomeroy coal bed (high volatile A bituminous coal; Monongahela Formation; Upper Pennsylvanian) of Kanawha County, West Virginia. The origin of the rodlets was determined by a comparative analysis of a medullosan (seed fern) stem from the Herrin (No. 6) coal bed (high volatile C bituminous coal; Carbondale Formation) from Washington County, Illinois. Rodlets are commonly concentrated in fusain or carbominerite layers or lenses in bituminous coal beds of the central Appalachian basin. Most of the rodlets examined in our study were probably derived from medullosan seed ferns. The three types of rodlets are distinguished on the basis of cellularity, morphology and fracture.The resin rodlets studied by us are noncellular and appear to be similar in properties and origin to those found in coal beds of the Middle and Upper Pennsylvanian of the Illinois basin. The resin rodlets extracted from the Pomeroy coal bed exhibit high relief and high reflectance when polished and viewed in reflected light; they are opaque in transmitted light. In cross section, the resin rodlets are oval to round and have diameters ranging from 60 to 450 μm. Many are solid, but some have vesicles, canals or cavities, which are commonly filled with clay, probably kaolinite. Typically, they have distinct fracture patterns (“kerfs”) in longitudinal and cross sections and many are characterized by dense (probably oxidized) rims. The orientation and amounts of void space and mineralization of resin rodlets in coal have resulted in much confusion in their recognition and classification. The resin rodlets are petrographically recognized as sclerotinites of the inertinite maceral group. We here propose that resin rodlets be assigned to the maceral variety of sclerotinites termed “resino-sclerotinite” because of their presumable resinous origin. Other investigators have confused some fusinitized resin rodlets with fungal masses, which have different morphological properties and which probably have different chemical properties. We here propose that such fungal masses be assigned to the maceral variety of sclerotinites termed “fungo-sclerotinite.”The sclerenchyma strands examined in our study are cellular, thick-walled, and crescent-shaped in cross section. They exhibit high reflectance and high relief and belong to semifusinite and fusinite of the inertinite maceral group. Sclerenchyma strands are commonly associated with resin canals in Medullosa and related seed-fern genera, which are common in coal balls of the Illinois basin. We here propose adoption of the maceral varietal terms “sclerenchymo-fusinite” and “sclerenchymo-semifusinite” for these bodies.The woody splinters in the Pomeroy coal bed are cellular and thin-walled and have scattered pits as much as a few microns in diameter. They are dark brown to black in transmitted light and commonly have a lower reflectance than the resino-sclerotinite and sclerenchymo-fusinite of the Pomeroy coal. The woody splinters belong to semifusinite and fusinite of the inertinite maceral group. The maceral varietal terms “xylemo-semifusinite” and “xylemo-fusinite” are here proposed for these bodies.Elemental chemical data for the resin rodlets of the Pomeroy coal bed of the central Appalachian basin indicate that resin rodlets have significantly lower atomic H/C and O/C ratios than do sclerenchyma strands and woody splinters. The lower atomic H/C and O/C ratios of the resin rodlets correlate with the highest reflectance. In the coal ball medullosan seed-fern stem from the Herrin (No. 6) coal bed of the Illinois basin, the reflectances of the resin rodlets, woody splinters and sclerenchyma strands are similar and comparable to those of associated vitrinite in the coal ball stem and in the attached coal. However, resin rodlets and sclerenchyma strands in the attached coal have significantly higher reflectances, similar to those of the Pomeroy coal.     

Magma type and tectonic setting discrimination using immobile elements

Five minor and trace elements have been variously combined to produce a set of binary diagrams in addition to total alkali-SiO₂ diagrams, that discriminate between fresh tholeiitic and alkali basalts. These diagrams are TiO₂-Zr, TiO₂-Y/Nb, P₂O₅-Zr, TiO₂-Zr/P₂O₅, and Nb/Y-Zr/P₂O₅. A clear discrimination between alkaline and tholeiitic basalts can be obtained, although no meaningful separation can be made between the broad groups of oceanic and continental basalts, of either magma type, on the diagrams. As these elements (Ti, P, Zr, Y and Nb) are generally considered immobile during alteration processes, it should be possible to distinguish the magma type of ancient basic volcanics that have been subjected to submarine weathering, spilitization and low-grade metamorphism.     

Some evidence of organized flow over natural waves

Measurements of the flow characteristics at 2 m over unobstructed wave surfaces on Lake Michigan were made using an anemometer-bivane as a velocity sensor. During one 40-min period of measurement, significant energy concentration was observed at the frequency of dominant surface waves in the vertical and cross wind spectra. Cross spectra between the surface elevation and vertical motions in the flow indicate that the surface lags the vertical motions by about 55 ° at the frequency of dominant waves.     

Tracing ground water input to base flow using sulfate (S, O) isotopes

Sulfate (S and O) isotopes used in conjunction with sulfate concentration provide a tracer for ground water contributions to base flow. They are particularly useful in areas where rock sources of contrasting S isotope character are juxtaposed, where water chemistry or H and O isotopes fail to distinguish water sources, and in arid areas where rain water contributions to base flow are minimal. Sonoita Creek basin in southern Arizona, where evaporite and igneous sources of sulfur are commonly juxtaposed, serves as an example. Base flow in Sonoita Creek is a mixture of three ground water sources: A, basin ground water with sulfate resembling that from Permian evaporite; B, ground water from the Patagonia Mountains; and C, ground water associated with Temporal Gulch. B and C contain sulfate like that of acid rock drainage in the region but differ in sulfate content. Source A contributes 50% to 70%, with the remainder equally divided between B and C during the base flow seasons. The proportion of B generally increases downstream. The proportion of A is greatest under drought conditions.     

CM carbonaceous chondrite falls and their terrestrial alteration

The CM carbonaceous chondrites provide unique insights into the composition of the protoplanetary disk, and the accretion and geological history of their parent C‐complex asteroid(s). Of the hundreds of CMs that are available for study, the majority are finds and so may have been compromised by terrestrial weathering. Nineteen falls have been recovered between 1838 and 2020, and there is a hint of two temporal clusters: 1930–1942 and 2009–2020. Falls are considered preferable to finds to study because they should be near pristine, and here this assumption is tested by investigating their susceptibility to alteration before recovery and during curation. CMs falling on the land surface are prone to contamination by organic compounds from soil and vegetation. Where exposed to liquid water prior to collection, minerals including oldhamite can be dissolved and most fluid mobile elements leached. Within days of recovery, CMs adsorb water from the atmosphere and are commonly contaminated by airborne hydrocarbons. Interaction with atmospheric water and oxygen during curation over year to decadal timescales can produce Fe‐oxyhydroxides from Fe,Ni metal and gypsum from indigenous gypsum and oldhamite. Relationships between the petrologic (sub)types of pre‐1970 falls and their terrestrial age could be due to extensive but cryptic alteration during curation, but are more likely a sampling bias. The terrestrial history of a CM fall, including circumstances of its collection and conditions of its curation, must be taken into account before it is used to infer processes on C‐complex parent bodies such as Ryugu and Bennu.     

Winchcombe: An example of rapid terrestrial alteration of a CM chondrite

Winchcombe is a CM chondrite that fell in England on February 28, 2021. Its rapid retrieval was well characterized. Within two polished sections of Winchcombe, terrestrial phases were observed. Calcite and calcium sulfates were found in a sample recovered from a field on March 6, 2021, and halite was observed on a sample months after its recovery from a driveway on March 2, 2021. These terrestrial phases were characterized by scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy. Calcite veins crosscut the fusion crust and therefore postdate it. The calcite likely precipitated in the damp environment (sheep field) where the meteorite lay for six days prior to its retrieval. The sulfates occur on the edges of the sample and were identified as three minerals: gypsum, bassanite, and anhydrite. Given that the sulfates occur only on the sample's edges, including on top of the fusion crust, they formed after Winchcombe fell. Sulfate precipitation is attributed to the damp fall environment, likely resulted from sulfide-derived H₂S reacting with calcite within the meteorite. Halite occurs as euhedral crystals only on the surface of a polished section and exclusively in areas relatively enriched in sodium. It was likely produced by the interaction of the polished rock slice with the humid laboratory air over a period of months. The sulfates, fusion crust calcite, and halite all post-date Winchcombe's entry into the Earth's atmosphere and showcase how rapidly meteorite falls can be terrestrially altered.     

Dating Palaeolithic sites in southwestern Crete,Greece

Discussions of dispersals of early hominins from Africa assume that Southwest Asia and the Arabian Peninsula were the primary passageways for migrations to Eurasia. The Mediterranean is usually viewed as a barrier to early hominin movements because pre‐sapiens hominins were thought to lack the technical means or the cognitive skills to construct boats. The discovery of early Palaeolithic artefacts in an archaeological survey on the Greek island of Crete challenges this view. Here we show that Palaeolithic artefacts in the Plakias region in southwestern Crete are associated with geological contexts that can be dated to the late Middle or early Late Pleistocene. Because Crete has been separated from the mainland throughout the Pleistocene, the presence of Pleistocene age artefacts there suggests that early hominins were able to cross open water. Copyright © 2011 John Wiley & Sons, Ltd.     

Measuring snow accumulation and ablation dynamics during rain-on-snow events: innovative measurement techniques

Rain-on-snow (ROS) is the primary generator of peak flow events in mountainous coastal regions of North America. Uncertainty remains as to the role of forest canopy interception leading up to and during ROS events. Much of this uncertainty can be attributed to a lack of suitable techniques to collect data during ROS, due in part to the dynamic nature of climatic conditions, particularly related to snow accumulation and melt. We supplemented a meteorological network with non-weighing snow melt lysimeters, suspended spring scales to measure snow throughfall and an automated time lapse photography network to monitor state of precipitation (rain vs. snow), snow accumulation/ablation, canopy interception and unloading of snow from the canopy. Image analysis software allowed for the extraction of data from images. Rapid loading and unloading of snow from the canopy, closely linked to changes in temperature, was observed using this approach. We were also able to continuously monitor throughfall snow water equivalent using low cost suspended spring scales. This experimental design allowed us to capture information previously unavailable without direct observation. Copyright © 2008 John Wiley & Sons, Ltd.