Pennsylvanian

Patterns of sedimentary trace-metal variation can provide information not only about benthic redox conditions, but also about other water-mass properties in ancient marine depositional systems. Trace metals such as Mo, U, V, and Re display conservative concentration profi les in the global ocean but varying concentration profi les in modern anoxic silled basins (e.g., the Black Sea, Cariaco Basin, and Framvaren Fjord) as a consequence of enhanced sedimentary uptake, water-mass mixing, microbial cycling, and other processes. Because basinspecifi c patterns of aqueous trace-metal concentrations can be recorded by the sediment, chemostratigraphic studies of ancient anoxic marine facies have the potential to provide information about the degree of water-mass restriction as well as secular changes in aqueous chemistry and basin hydrography. In the Upper Pennsylvanian Hushpuckney and Stark shales of midcontinent North America, strong positive covariation among major trace metals supports extraction from a water mass of unmodifi ed "normal" seawater chemistry with control of sedimentary trace-metal uptake primarily by benthic redox variation.

The cauline and leaf cushion morphology of Lepidophloios trees from lower and middle Pennsylvanian, American coal swamps
are described and compared with other Carboniferous specimens. More than one hundred specimens were anatomically studied from twenty-six localities in ten coals extending stratigraphically from the Magoffin Member, Breathitt Formation, Pottsville Group in the Appalachian Coal Province to the "Baker" Coal Member, Lisman Formation in the upper Desmoinesian Series of the midcominent Interior Coal Provinces. With few exceptions the stems are referable to one species along this entire stratigraphic range. The two previously described American species of Lepidophloios, L. kansanus (C. FELIX) EGGERT and L. pachydermatikos ANDREW & MURDY are placed in synonymy with Lepidophloios hallii (EVERS) comb. nov. which was originally described as a species of Lepidodendron. An emended diagnosis of Lepidophloios hallii is given and two taxa based on partially preserved specimens without leaf cushions are transferred from Lepidodendron to Lepidophloios as L. wilsonii (ANDREWS & BAXTER) comb. nov. and L. johnsonii (ARNOLD) comb. nov. on the basis of their cauline anatomy.
          The mature tree of Lepidophloios hallii attained a height of 10-20 m. A reconstruction of the crown suggests upright, compact, infrequent isotomous branching consistent with the lack of secondary supportive tissues in the branches. Most of the crown support was derived from the thick outer cortex. Cones were borne laterally in the upper crown and / or terminally on ultimate divisions of the crown. Specimens attributed to Lepidophloios kansanus are from the main trunk and lower part of the crown; those described as Lepidophloios pachydermatikos represent the middle and upper crown. There is no secondary xylem and very little periderm in these crown branches. Transitions between the two have been established and provide further documentation of positional differences in the tree of pith zonation, stelar dimensions, presence or absence of secondary growth and lateral branches, and depth of periderm initiation. Periderm development in Lepidophloios hallii originated from a bifacial phellogen. The size and degree of imbrication of leaf cushions are related to total size of the primary body and position on the cauline systems, hence to vegetative determinate growth. There is no evidence of continued leaf cushion expansion concomitant with secondary development of the stem. Leaf cushion morphology and their cuticles are very similar to those of Lepidophloios laricinus STERNBERG which is based on compressions and impressions.
          The most similar anatomically preserved European species to Lepidophloios hallii are L. harcoztrtii (WITHAM) SEWARD & HILL
and L. fuliginosus (WiLLIAMSON) SEWARD. All of these Upper Carboniferous species differ anatomically and morphologically
from the European Lepidophloios Wuenchianus (CARRUTHERS) SEWARD & HILL and L. scottii GORDON, primar ily from the Lower Carboniferous, and from the American L. johnsonii from the lower Pennsylvanian. These two groups of species, L. harcourtii and L. wuenchianus, overlap stratigraphically in the Namurian and Westphalian A. The L. w uenchiantts group is not known from coal swamp environments. The L. harcourtii group constitutes a major vegetationa! component of Euramerican coal swamps, with L. hallii stratigraphicall y complementing L. harcourtii and L. fuliginosus prior to and during the middle Pennsylvanian (Desmoinsian Series or U.S.G.S. interval C).

This Atlas of Permo-Carboniferous Paleogeographic Maps shows the changing paleogeography from the Early Mississippian (Tournasian, 352.3 Ma) to the Early Permian (Kungurian, 273.1 Ma).  The maps are from volume 4 of the PALEOMAP PaleoAtlas for ArcGIS (Scotese, 2014). Absolute age assignments are from Gradstein, Ogg & Smith (2008). 

The following maps are included in the Atlas of Permo-Carboniferous Paleogeographic Maps:

Map 53  Early Permian (Kungurian, 273.1 Ma) Highstand Systems Tract
Map 54  Early Permian (Artinskian, 280 Ma) Maximum Flooding Surface 
Map 55  Early Permian (Sakmarian, 289.5 Ma) Maximum Flooding Surface
Map 56  Early Permian (Asselian, 296.8 Ma) Sakmarian Supersequence Boundary & Maximum Flooding Surface
Map 57  Late Pennsylvanian (Gzhelian, 301.2 Ma) Asselian Supersequence Boundary & Maximum Flooding Surface
Map 58  Late Pennsylvanian (Kasimovian, 305.3 Ma) Maximum Flooding Surface
Map 59  Middle Pennsylvanian (Moscovian, 309.5) Transgressive Systems Tract
Map 60  Early Pennsylvanian (Bashkirian, 314.9 Ma) Bashkirian Supersequence Boundary & Maximum Flooding Surface
Map 61  Late Mississippian (Serpukhovian, 323.2 Ma) Maximum Flooding Surface
Map 62  Middle Mississippian (late Visean, 332.5 Ma) Highstand Systems Tract
Map 63  Middle Mississippian (early Visean, 341.1 Ma) Maximum Flooding Surface
Map 64  Early Mississippian (Tournasian, 352.3 Ma) Maximum Flooding Surface


This work should be cited as
Scotese,  C.R., 2014.  Atlas of Permo-Carboniferous Paleogeographic Maps (Mollweide Projection), Maps 53 – 64, Volumes 4, The Late Paleozoic, PALEOMAP Atlas for ArcGIS, PALEOMAP Project, Evanston, IL.

These maps (rectilinear projection) are from the PALEOMAP PaleoAtlas for ArcGIS (Scotese, 2013a-f).  This is a digital atlas of plate tectonic, paleogeographic, and paleoclimatic reconstructions designed for use with the GIS software, ArcMap (ESRI).  Table 1 lists the various types of maps that comprise the PALEOMAP PaleoAtlas.  The maps included in this folio are highlighted in bold text (Table 1).
The last map in each folio is a rectilinear graticule that can be overlain on the maps to provide a geographic reference frame.  A rectilinear projection was used because it can be easily georeferenced in ArcMap and transformed into a variety of other map projections.  The rectilinear map projection can also be directly “wrapped” onto a spherical projection, like the oneused by Google Earth. A set of Google Earth paleoglobes has made from the maps in this folio. These Google Earth paleoglobes can be downloaded at: www.globalgeology.com. 
If the map you need is missing, or if there doesn’t seem to be a map folio for the exact time interval of interest, please contact me ([email protected]). Table 2 lists all the time intervals that comprise the PALEOMAP PaleoAtlas for ArcGIS. The PaleoAtlas contains one map for every stage in the Phanerozoic, as well as 6 maps for the late Precambrian.  Eventually, Map Folios, like this one, will be published for every time interval in the PALEOMAP PaleoAtlas.  The following section is a brief description of the maps that makeup the Map Folio.

This map folio should be referenced as:
Scotese, C.R., 2013. Map Folio 57, Late Pennsylvanian (Gzhelian 301.2 Ma), PALEOMAP PaleoAtlas for ArcGIS, volume 4, Late Paleozoic Paleogeographic, Paleoclimatic and Plate Tectonic Reconstructions, PALEOMAP Project, Evanston, IL.

During construction work between 2010 and 2012 a large road cut in Flöha enabled collection of a diverse middle
Pennsylvanian flora embedded in pyroclastic deposits. Fossil plants consisting of sphenopsids, ferns, lycopsids and gymnosperms, confirm and delimit the stratigraphic age of the Flöha-Formation as Bolsovian, which is in accordance with the radiometric age of 310±2 Ma obtained from the plant-bearing horizon. Several plants were detected for the first time from the Flöha-Formation, such as various sphenopterid, mariopterid and neuropterid pteridophylls, calamitalean and cordaitalean fructifications and woods, sphenophyllalean leaves and strobili, zygopterid and psaroniaceous ferns. Preservational forms comprise compression-impression types, casts and also permineralised
stems. The pyroclastics at the outcrop were described as being of the palaeorhyolite type Schweddey and consist of more or less welded lapilli-containing, poorly sorted ash tuffs, whose origin is attributed to a pyroclastic density current. This palaeorhyolite was compared with other palaeorhyolites in the region and is best understood as a separate volcanic emplacement event - distinct in space and time from other palaeorhyolites.
Our results and considerations thus challenge the Permian stratigraphic age of the fossil ferns (Tubicaulis, Zygopteris)
described by Cotta (1832) from the Gückelsberg quarry at Flöha.

The Carboniferous, the time of Earth’s penultimate icehouse and widespread coal formation,
was dominated by extinct lineages of early-diverging vascular plants. Studies of nearest living
relatives of key Carboniferous plants suggest that their physiologies and growth forms differed
substantially from most types of modern vegetation, particularly forests. It remains a matter of
debate precisely how differently and to what degree these long-extinct plants influenced the
environment. Integrating biophysical analysis of stomatal and vascular conductivity with
geochemical analysis of fossilized tissues and process-based ecosystem-scale modeling yields a
dynamic and unique perspective on these paleoforests. This integrated approach indicates that
key Carboniferous plants were capable of growth and transpiration rates that approach values
found in extant crown-group angiosperms, differing greatly from comparatively modest rates
found in their closest living relatives. Ecosystem modeling suggests that divergent stomatal
conductance, leaf sizes and stem life span between dominant cladeswouldhave shifted the balance
of soil–atmosphere water fluxes, and thus surface runoff flux, during repeated, climate-driven,
vegetation turnovers. This synthesis highlights the importance of ‘whole plant’ physiological
reconstruction of extinct plants and the potential of vascular plants to have influenced the Earth
system hundreds of millions of years ago through vegetation–climate feedbacks

This paper deals with compression fossils of two Late Carboniferous herbaceous lycopods, New fertile material of
Selaginellites gutbieri (G6ppert, 1837) Kidston, 1911 was collected from its type locality Oelsnitz (Westphalian D; Erzgebirge- Basin). The three-dimensionally preserved strobili clearly show micro- and megasporangia. In addition a sterile large-leaved form is described from the Westphalian D of the Saar Basin.

—Taxonomic analysis is provided for a Middle Pennsylvanian macrofloral assemblage collected from clastic wetland deposits in Clay County, Indiana, on the eastern margin of the Illinois Basin. Adpressed plant fossils were recovered from four distinct beds in the lowermost Staunton Formation, positioned above the Minshall Coal (uppermost Brazil Formation), part of a succession deposited near the Atokan-Desmoinesian boundary. The assemblage of 22 fossil-taxa is dominated by pteridosperms (including Neuropteris flexuosa, Macroneuropteris scheuchzeri, Alethopteris densinervosa, Neuropteris ovata, Eusphenopteris neuropteroides, and Neuropteris missouriensis) with lesser cordaitaleans (Cordaites spp. indet.) and sphenopsids (particularly Sphenophyllum cuneifo-lium). Lycopsids are uncommon, and ferns are rare. In contrast, the microfloral assemblage from the Minshall Coal and overlying clastic units is dominated by lycopsid and tree fern spores. Comparisons with established biozonation schemes yield different ages depending on the regional biostratigraphic framework used: (1) latest Bolsovian (Radiizonates difformis Biozone, American microfloras); (2) latest Bolsovian or earliest Asturian ('Neuropteris' rarinervis Biozone, Appalachian Basin macrofloras); or (3) earliest Asturian (Linopteris obliqua Biozone, European macrofloras). The placement and correlation of the Bolsovian-Asturian and Atokan-Desmoinesian boundaries, which have traditionally been equated by palynology, are evaluated in the context of this discordance. Several revised stratigraphic scenarios are proposed for this interval in the Illinois Basin, which is being increasingly recognized as a time of significant environmental change throughout Euramerica. Homotaxial comparisons with European macro-floral assemblages indicate that, of the 18 biological taxa recorded, between 14 and 17 (78–94%) also are common in coeval wetland deposits in Europe. The similarities exemplify the spatial conservatism and low diversity of wetland plant communities over vast areas of tropical Euramerica, a manifestation of the intrinsically stressful conditions that characterize such habitats, and indicates that neither the Laurentian Shield nor the Appalachian-Variscan Mountains were an insurmountable barrier to plant dispersal during the Middle Pennsylvanian.

Premise of research. The Late Paleozoic Ice Age was the last extensive pre-Pleistocene ice age. It includes many climate changes of different intensities, permitting examination of many and varied biotic responses. The tropical Pennsylvanian Subperiod, usually visualized as one vast wetland coal forest, in fact also was dominated, periodically, by seasonally dry vegetation that, in turn, covered most of the central and western Pangean supercontinent. Equatorial wetland and dryland biomes oscillated during single glacial-interglacial cycles. This recognition changes understanding of the Coal Age tropics; examination of their spatiotemporal patterns indicates that these vegetation types responded differently to global environmental disturbances and long-term trends and points to potentially different underlying controls on evolutionary histories of their component lineages.

Fossil plants have been collected and described from strata near the Pennsylvanian-Permian boundary in three
areas of San Juan County, Utah. Collections made near Indian Creek east of Canyonlands National Park comprise
mainly tree fern foliage and sphenopsids from one stratigraphic level, and large logs of conifers with rare conifer
foliage from a higher level. A site on Lime Ridge west of Bluff, Utah, yielded abundant large branches of walchian
conifers together with calamitaleans and cordaitalean foliage. Sites in Valley of the Gods State Park, west of Lime
Ridge, produced mainly stems, with variable occurrences of foliage. Most of the stems are calamitalean or the
large tree fern Caulopteris, but a single medullosan pteridosperm specimen also was found, as were several small
fragments of the lycopsid Sigillaria. Tree fern foliage, Pecopteris, rare neuropterid foliage, and fragments of leafbearing
conifer branches also were identified. Thus, our collections contain a mixture of plants adapted to seasonally
dry conditions (conifers and possibly cordaitaleans) and those requiring wet substrates (calamitaleans, tree
ferns, lycopsids and pteridosperms). Red beds, dune sands, loess, and gypsum indicate aridity, on average, but with
intervals of more humid conditions. The combination implies an arid eolian depositional system traversed at times
by streams sourced on the Uncompahgre highland.

The black shale submember of core shales of Pennsylvanian Kansas-type cyclothems is highly enriched in redox-sensitive trace elements (TEs) relative to the overlying gray shale submember as well as to many other modern and ancient organic-rich deposits. Controls on trace-element behavior in the black shale can be inferred from trace-element enrichment factors (EFs, relative to gray shale) and the relationship of TEs to total organic carbon (TOC). Most TEs conformed to one of two patterns:

The Pennsylvanian portion of the Late Paleozoic Ice Age was characterized by stratigraphic
repetition of chemical and siliciclastic rocks in the equatorial regions of the Pangean
interior. Known as ‘‘cyclothems’’, these stratigraphic successions are a 105 yr-record of
glacial waxing and waning, superimposed on longer term, 106 yr intervals of global
warming and cooling and a still longer term trend of increasing equatorial aridity. During
periods of maximum ice–minimum sea level, the interior craton was widely exposed.
Epicontinental landscapes were initially subjected to dry subhumid climate when first
exposed, as sea level fell, but transitioned to humid climates and widespread wetlands
during maximum lowstands. During interglacials (ice-minima) seasonally dry vegetation
predominated. The wetland and seasonally dry biomes were compositionally distinct and
had different ecological and evolutionary dynamics.

PREMISE OF THE STUDY: Noeggerathiales are an extinct group of heterosporous shrubs and trees that were widespread and diverse during the Pennsylvanian– Permian Epochs (323–252 Ma) but are of controversial taxonomic affi nity. Groups proposed as close relatives include leptosporangiate ferns, sphenopsids, progymnosperms, or the extant eusporangiate fern Tmesipteris. Previously identifi ed noeggerathialeans lacked anatomical preservation, limiting taxo-nomic comparisons to their external morphology and spore structure. We here document from the upper Permian of China the fi rst anatomically preserved noeggerathialeans, which enhance the perceived distinctiveness of the group and better indicate its systematic affi nity. METHODS: We describe in detail the newly discovered, anatomically preserved heterosporous strobilus Dorsalistachya quadrisegmentorum , gen. et sp. nov., and redescribe its suspected foliar correlate, the pinnate leaf Plagiozamites oblongifolius. KEY RESULTS: Plagiozamites possesses an omega (Ω)-shaped vascular trace and prominent cortical secretory cavities—a distinctive anatomical organization that is echoed in the newly discovered strobili. Dorsalistachya strobili bear highly dissected sporophylls alternately in two vertical rows, suggesting that they are homologs of leaf pinnae. If so, the " strobilus " is strictly a pseudostrobilus and consists of sporangium-bearing units that are one hierarchical level below true sporophylls. The " sporophylls " bear four microsporangia on the lower (abaxial) surface, occasionally interspersed with short longitudinal rows of megasporangia. A single functional megaspore develops within each winged megasporangium, suggesting adaptation for dispersal as a single unit. CONCLUSIONS: Dorsalistachya presents a unique combination of reproductive features that amply justifi es establishment of a new family, Dorsalistachyaceae. Noeg-gerathiales represent a distinct taxonomic Order of free-sporing plants that most resembles early-divergent eusporangiate ferns and the more derived among the extinct progymnosperms. By the early Permian, noeggerathialeans had attained levels of reproductive sophistication similar to the most derived among the Pa-leozoic sphenophytes and lycophytes, but their heterosporous life history may have contributed to their extinction during the Triassic climatic aridifi cation.

As part of an on-going multidisciplinary investigation of the Bristol Coalfield we present a detailed account of assemblages of megaspores and large pollen grains from the mid-Bolsovian to late Asturian Warwickshire Group (Winterbourne, Pennant Sandstone and Grovesend formations). The megaspore assemblages show certain similarities to those from the well documented, and partly coeval, sequence in the nearby Forest of Dean Coalfield. However, the Bristol Coalfield megaspore assemblages are generally less diverse. We consider the palaeoecological implications of the megaspore assemblages and conclude that differing depositional settings had different vegetational successions (including differences in the composition and diversity of megaspore-producing plants). A consideration of megaspore biostratigraphy suggests that the uppermost Pennant Sandstone Formation may be of early Asturian age, suggesting that the postulated gap between the Pennant Sandstone Formation and overlying Grovesend Formation is smaller than previously suggested. We also report the first European occurrence of the large enigmatic pteridosperm pollen grain Parasporites maccabei.

Patterns of sedimentary trace-metal variation can provide information not only about benthic redox conditions, but also about other water-mass properties in ancient marine depositional systems. Trace metals such as Mo, U, V, and Re display conservative concentration profi les in the global ocean but varying concentration profi les in modern anoxic silled basins (e.g., the Black Sea, Cariaco Basin, and Framvaren Fjord) as a consequence of enhanced sedimentary uptake, water-mass mixing, microbial cycling, and other processes. Because basinspecifi c patterns of aqueous trace-metal concentrations can be recorded by the sediment, chemostratigraphic studies of ancient anoxic marine facies have the potential to provide information about the degree of water-mass restriction as well as secular changes in aqueous chemistry and basin hydrography. In the Upper Pennsylvanian Hushpuckney and Stark shales of midcontinent North America, strong positive covariation among major trace metals supports extraction from a water mass of unmodifi ed "normal" seawater chemistry with control of sedimentary trace-metal uptake primarily by benthic redox variation.

The biogeographic distribution of foraminifers and their belonging to either the southern or northern margins of the Paleo-Tethys are used here for paleogeographic reconstructions of Iran during the Carboniferous. Lower Carboniferous foraminiferal assemblages from northern and central Iran show a cosmopolitan character and affinities to both the southern and northern borders of the Paleo-Tethys. Hence, in the Early Carboniferous Iran occupied an intermediate southern latitude position, forming part of Gondwana. This conclusion is consistent with the Late Ordovician to Early Carboniferous drift history of Iran based on paleomagnetic data. In the Late Carboniferous, the foraminiferal affinities of northern and central Iran with the northern part of Paleo-Tethys suggest that Iran separated from Gondwana and moved northwards to a lower latitude. This separation is also evidenced by the Upper Carboniferous coal-bearing sandstones of the Sardar Formation and sandstones with high degree of chemical weathering, which would indicate warm and humid conditions. Considering the composition of foraminiferal fauna along with the evidence of magmatic activities in northwest Iran, it can be inferred that the commencement of the Neo-Tethys opening and continental break-up in Iran occurred sometime in the Late Carboniferous, which contradicts the previous claims that the separation of Iran from Gondwana occurred in Permian and/or Triassic times.

The black shale submember of core shales of Pennsylvanian Kansas-type cyclothems is highly enriched in redox-sensitive trace elements (TEs) relative to the overlying gray shale submember as well as to many other modern and ancient organic-rich deposits. Controls on trace-element behavior in the black shale can be inferred from trace-element enrichment factors (EFs, relative to gray shale) and the relationship of TEs to total organic carbon (TOC). Most TEs conformed to one of two patterns:

The Hushpuckney Shale Member of the Swope Formation (Missourian Stage, eastern Kansas) is the core shale of a Kansastype cyclothem, formed during the late transgressive to early regressive phases of a Late Pennsylvanian glacio-eustatic cycle. Coeval high-frequency climato-environmental dynamics of the Midcontinent Seaway are preserved in the KGS Orville Edmonds No. 1A study core as centimeter-scale variation in major components (organic carbon, authigenic sulfides and phosphate, detrital siliciclastics), organic macerals, trace-element redox proxies (Mo, U, V, Zn), and ichnofabric features. Benthic O 2 levels declined sharply from the base of the black shale (0 cm), went sulfidic at f4 cm, and reached a redox minimum at f21 cm; above this level, redox potential gradually rose, fluctuating between sulfidic and nonsulfidic conditions from f35 cm to the black shale/gray shale contact at 52 cm. Onset of dysoxic conditions at that contact allowed establishment of a benthic community of soft-bodied organisms comprised of deep-tiered tracemakers tolerant of low-O 2 conditions (Trichichnus), and shallow-tiered tracemakers favoring ''soupground'' (Helminthopsis) or ''firmground'' substrates (the Zoophycos -Phycosiphon -Schaubcylindrichnus -Planolites association). Most geochemical records exhibit a ''low-order'' cycle spanning the full 52 cm thickness of the black shale submember, reflecting a dominant glacio-eustatic control. The base and top of the black shale submember record lateral migration of the pycnocline across the Midcontinent Shelf during the transgressive and regressive phases, respectively. The maximum flooding surface (MFS) is at f17 -23 cm, an interval containing the euxinic peak and characterized by high concentrations of illite (representing a cratonic siliciclastic flux) and terrestrial organic macerals, the product of transient increases in humidity, weathering rates, and the export of coal-swamp vegetation associated with the interglacial highstand of the Swope cyclothem. Although a transgressive ''surface of maximum starvation'' (SMS) cannot be confidently identified, a phosphate-rich ''regressive condensation surface'' at f28 -34 cm records pycnoclinal weakening due to increased aridity associated with renewed southern hemisphere icesheet growth; a correlative shift in dominance from terrestrial-to marine-derived organic macerals reflects increased upwelling of nutrient-rich deepwaters and enhanced primary productivity. Penecontemporaneous paleogeographic and -climatic factors (e.g., semirestricted circulation, monsoonal precipitation) predisposed the Midcontinent Seaway toward sensitivity to high-frequency climato-0009-2541/$ -see front matter D (J.C. Hower).

The use of molybdenum isotope data (δ 98 Mo) from organic-rich shales to draw inferences concerning marine paleoredox conditions at a global scale is predicated upon the assumptions of (1) a residence time of Mo in seawater much greater than the ocean mixing time, and (2) quantitative removal of Mo from a strongly euxinic ([H 2 S] aq > 11 μM) water column to the sediment, thus preserving the seawater δ 98 Mo signature. In this study we analyze Mo isotopic variation in the Hushpuckney Shale, a 73-cm-thick unit representing the late transgressive to early regressive stages of a glacio-eustatic cyclothem (Swope Formation) deposited in the Late Pennsylvanian Midcontinent Sea (LPMS) of North America. The Hushpuckney can be subdivided into four stratigraphic zones of distinctive geochemical character. Zones I and III, which accumulated under weakly euxinic conditions, acquired relatively high δ 98 Mo values (+0.9 to +1.1‰), whereas Zone II, which accumulated under intensely euxinic conditions, acquired lower δ 98 Mo values (~+0.6‰). Zone IV, which accumulated under suboxic conditions in the water column, acquired the heaviest δ 98 Mo values (+1.1 to + 1.8‰). These results contrast with the pattern of redox -δ 98 Mo covariation in modern marine environments, in which the heaviest δ 98 Mo values are found in the most intensely euxinic facies. We evaluate three different hypotheses to account for the Mo isotopic patterns of the Hushpuckney Shale. One hypothesis, seawater-freshwater mixing, is rejected owing to isotopic mass balance considerations. A second hypothesis is a local control on δ 98 Mo by water-column redox cycling of Mn, with particulate Mnoxyhydroxides adsorbing isotopically light Mo and transferring it to the sediment, a process that was most active during deposition of Zone II. The significance of this scenario is that euxinic black shales may not reliably record global seawater δ 98 Mo in areas where a Mn-particulate shuttle is operative. A third hypothesis is based on rapid secular variation of the Mo isotope composition of Late Pennsylvanian global seawater. In order to account for δ 98 Mo trends within the Hushpuckney Shale, seawater δ 98 Mo must have varied by~1.2‰ at a~100-kyr timescale, which would have been possible only if the residence time of Mo in Late Pennsylvanian seawater was b 100 kyr. Although both the second and third hypotheses are viable based on the present limited δ 98 Mo dataset, we discuss how each model might be tested through additional Mo isotope data.

This volume presents eight articles on the Pennsylvanian-Permian geology and paleontology of the
Robledo Mountains in Doña Ana County, southern New Mexico. The reported research resulted from a federally-
funded study of the trace fossils in and around the Prehistoric Trackways National Monument (PTNM). We
divide the overview by the main topics addressed—stratigraphy, sedimentology, paleobotany, micropaleontology,
biostratigraphy and ichnology―and draw attention to the most significant research results. These indicate that the
identification of glacio-eustatically driven sedimentary cyclicity in the Robledos Lower Permian strata, paralleling
that seen in mid-continent and Appalachian basin cyclothems of Pennsylvanian age, is problematic. There may
be some kind of allocyclic signature in the Robledo sections, but autocyclic drivers clearly were important forces
in the local Early Permian sedimentary history. The red-bed fossil assemblages in the PTNM were early fit into
a rather simple model of intertidal flat depositional environments, but studies here indicate much greater depositional
complexity, and identify what are likely a mosaic of local paleonenvironments and taphonomic settings in
which the trace fossils and red-bed plant assemblages accumulated. The Early Permian geological record indicates
episodically increasing seasonality and climatic dryness around the equatorial regions of central and western
Pangea, a trend that began in the late Middle Pennsylvanian. During this period of warming, terrestrial floras
became increasingly heterogeneous spatially, and the Robledo paleofloras fit that pattern. Precise and extensive
age data for the Hueco Group section based on non-fusulinid and fusulinid foraminiferans indicate that the base
of the Leonardian (Artinskian) is very close to the base of the Robledo Mountains Formation. This means the
upper part of the local Hueco section is Leonardian, not Wolfcampian as long supposed.

Sonapteris gen. nov. is established for two new species S. barthelii sp. nov. and S. pilsensis sp. nov. from the Bolsovian and Westphalian D of the Pilsen Basin, Czech Republic. Sonapteris barthelii sp. nov. and S. pilsensis sp. nov. were studied palynologically and morphologically. Both species are based on fertile specimens, which show branching systems bearing fertile organs, annulate sporangia and spores of a botryopterid type. Sonapteris gen. nov. is assigned to the family Botryopteridaceae. Whereas S. barthelii shows great similarities to the lower Carboniferous species B. antiqua, S. pilsensis does not show superficial similarities to any botryopterid species in general view. The anatomy of both new species remains unknown, and so it is impossible to place them in the genus Botryopteris Renault. In situ spores isolated from S. barthelii belong to the dispersed genus Leiotriletes-Granulatisporites-type. Different stages of maturity were observed in the spores isolated from S. pilsensis. The first type consists of laevigate spores closely comparable to several species of the dispersed genus Calamospora (relatively immature forms); the second, intermediate type consists of scabrate, microgranulate to microverrucate spores that can be correlated with the dispersed genera Verrucosisporites, Apiculatisporis or Planisporites; and the third (fully matured) type consists of clavate, baculate to spinate spores that belong to the dispersed genus Raistrickia. Such ontogenetic stages of botryopterid spores are described for the first time and they resemble similar maturity stages of spores of Senftenbergia plumosa. Sonapteris barthelii may represent a liana-like or epiphytic kind of fern, that grew on Psaronius trunks with Pecopteris tuffitica-type fronds. However, the general habit of S. barthelii remains unknown. D

Carbonate mounds are widespread in many places around the world and are especially well exposed in the Cantabrian Mountains, northern Spain. This study focuses on the composition and growth dynamics of two large mound complexes well exposed near the village of Puebla de Lillo, 70 km northeast of León, and evaluates the impact of sea level, accommodation, and siliciclastic input on mound growth.

This work presents a new age framework for the main Bashkirian glacio-eustatic transgression in Argentina, including the first absolute age for the Jejenes Formation, San Juan Province, based on radiometric dating of a crystal-rich tuff, supported by palynological and palaeofloristic studies, and presented within a revised palaeogeographic setting. The Jejenes Formation represents the glacial to postglacial fill of the Quebrada Grande palaeofjord carved in the Eastern Precordillera. The succession has been subdivided into five stages, the youngest of which suggests a previously unrecognised glacial event for this locality. Six productive levels for palynology were found within proglacial strata, and in the base and top of the succeeding interglacial stage. Palynoassemblages are characterized by poorly preserved trilete spores and monosaccate pollen grains along with a large amount of terrestrial phytoclasts. Main species indicating the Raistrickia densa-Convolutispora muriornata SubZone (DMa SZ) are Vallatisporites ciliaris, Cristatisporites rollerii, C. stellatus, C. chacoparanensis, C. inconstans and monosaccates such as Circumplicatipollis plicatus. This DMa SZ is estimated as Serpukhovian/Bashkirian and characterizes the glacial-related Guandacol Formation and equivalents units of the western Paganzo Basin. A tuffaceous level in the proglacial unit, bearing platyspermic seeds, plant remains and palynomorphs, yielded first-cycle volcanic zircons that were analysed by SHRIMP. An absolute age of 321.3 ± 5.3 Ma confirms a Bashkirian age for the main postglacial transgression in the Paganzo Basin, and offers a novel calibration for the palynoassemblages of DMa SZ that occurs elsewhere in Western Argentina.

The first record of microforaminiferal linings from the early Pennsylvanian of Argentina is presented as consisting of Trochospiral Type I, Planospiral Type II and cf. Uniserial indet. (sensu Stancliffe) forms while associated with acritarchs, prasinophytes, freshwater algae, spores and pollen grains. Microforaminiferal linings and associated microflora were obtained from the well core YCF.CO3 borehole (interval of 850–851.5 metres below drill floor), which comprises the lower part of the Ordóñez Formation (Chacoparaná Basin). This association documents the development of estuarine or shallow marine environments in the western part of the basin during the Pennsylvanian (Bashkirian?). The origin of these environments was associated with the final phases (transgressions) of the Carboniferous glaciation of Gondwana, documented in the diamictites of the Ordóñez Formation.

We document body fossils of the xiphosurid (horseshoe crab) Euproops danae Meek and Worthen from
lacustrine black shale of the Missourian interval of the Beeman Formation near Alamogordo, New Mexico. These xiphosaurids,
associated with conchostracans, bivalves, microconchids, fish scales and a paleoflora, are from a likely freshwater lake
deposit. This is the first report of E. danae from the western USA and the first documentation of xiphosurid body fossils in the
Pennsylvanian of New Mexico.

The Late Pennsylvanian Midcontinent Sea (LPMS) of North America, which existed during glacioeustatic highstands of the late Paleozoic ice age, was an immense (>1 × 10 6 km 2) cratonic interior sea exhibiting large-scale estuarine circulation, with a low-salinity surface plume overlying a high-salinity, anoxic, deep water mass. As in river estuaries, these conditions resulted in trapping and recycling of nutrients and organic-reactive elements (e.g., trace metals such as Mo, U, and Zn) in the subpycnoclinal water mass, leading to total organic carbon (TOC) to 40% and peak trace metal enrichment factors (EFs) of 540 (Mo), 73 (U), and 75 (Zn) in the black shale facies of the Hushpuckney Shale. Trace metal EFs increase gradually from distal (Oklahoma) to proximal (Iowa) areas of the Midcontinent Shelf before decreasing abruptly in the Illinois Basin, located to the east of the Mississippi River Arch (MRA). Owing to similar productivity (TOC) and redox (Fe T /Al) proxy values on both sides of this arch, the large differences in trace metal EFs are interpreted to reflect divergent deep-water chemistries; specifically, much larger aqueous trace metal inventories on the Midcontinent Shelf than in the Illinois Basin. This condition implies that (1) deep waters of the Midconti-nent Shelf and Illinois Basin were physically separated by the MRA, demonstrating its existence as a positive bathymetric feature during the Late Pennsylvanian, and (2) the saltwater wedge to the west of the MRA functioned as a nutrient trap in which organic-reactive trace metals were strongly concentrated through water-column recycling.

Late Pennsylvanian seep limestones (ca. 300 Ma) enclosed in the Ganigobis shales in southern Namibia formed by microbial activity. The process that induced carbonate precipitation was the anaerobic oxidation of methane. The presence of 13C-depleted pentamethylicosane (PMI) (–113‰) and a mixture of crocetane and phytane (–112‰) in concert with similarly 13C-depleted pseudohomologous series of regular isoprenoids reveals that methanotrophic archaea oxidized methane anaerobically at the ancient seep site. Biphytane and a C39 pseudohomologue are other archaeal molecular fossils with δ13C values of –99‰ and –97‰, respectively. The former presence of sulfate reducing bacteria as the syntrophic partners of methanotrophic archaea in the anaerobic oxidation of methane is indicated by isotopically depleted iso- and anteiso-alkanes. These compounds most probably derive from non-isoprenoidal monoethers and diethers, synthates of sulfate-reducing bacteria. These fi ndings show that anaerobic oxidation of methane is at least 300 m.y. old, extending the record of this process for ~140 m.y. As the molecular fossils of archaea and bacteria are preserved in a product of their own metabolic activity (i.e., methane-derived carbonates with δ13C values as low as –51‰), the syngenicity of molecular fossils and enclosing deposits is unambiguous. This reveals that microbially formed rocks can represent excellent archives for studying past biogeochemical processes

In this study, we identify endolithic microbial borings preserved as fluid inclusions in Pennsylvanian and Permian brachiopods from the subsurface of western Kansas. Endolithic microbial boring is a new biologically controlled mode of formation for inclusion vacuoles. The microborings are preserved as three types of linear, curved, and branched arrays of tubular fluid inclusions, each with a distinct diameter. Each of the thousands of microborings observed in 60 brachiopod fragments has changed shape by forming calcite partitions that have divided the original tubules into separate aligned fluid inclusions. On average, only 35% of the original lengths of the microborings are preserved as fluid inclusions; values range from less than 5% to about 85%. Enlarged diameters of inclusions, variable vapor-to-liquid ratio in paired inclusions, and low salinities of inclusions indicate that closed-system necking down is one of the mechanisms responsible for alteration of the microborings. Preservation of parallel walls, fillings with luminescent calcite and high salinity of included fluid indicate that open-system cementation is the other mechanism responsible for alteration of the microborings. As most inclusions have leaked and refilled or stretched during thermal re-equilibration, these fluid inclusions are not particularly reliable as records of diagenetic history. The linear arrays of fluid inclusions that remain after alteration of the original microboring are excellent as trace fossils of microbial activity. The record preserved here indicates how fluid-inclusion techniques can be applied to identify and determine the timing of entrapment of microbial trace fossils in ancient Earth and extraterrestrial materials.

Filtration models make several predictions concerning the distribution of crinoids among benthic habitats: (1) generally, higher energy shoreward settings should contain crinoid assemblages dominated by taxa with dense mesh filtration fans; (2) generally, lower energy offshore settings should be dominated by crinoids with open mesh filtration fans; (3) diversity should be highest in nearshore settings, which generally contain low energy microhabitats within high energy settings where both dense fan and open fan forms can co-occur, whereas offshore assemblages should be dominated by open fan taxa; thus, open fan forms should be more eurytopic than dense fan forms. Also, previous empirical models for crinoid distribution patterns note that nearshore assemblages are dominated by large forms whereas offshore assemblages are dominated by small forms. Filtration fan morphology and body size interact significantly to determine how and where crinoids feed and thus are used here as criteria for distinguishing late Paleozoic crinoid guilds. The distribution patterns of crinoid taxa and guilds among the benthic paleocnvironments of the Upper Pennsylvanian (Missourian) Stanton Formation were used to test the predictions of the filtration models.

Coordinated stasis is a pattern of long-term, multispecies evolutionary and ecological stability bounded by rapid turnover events. One class of models proposed to explain the paleoecological pattern of biofacies stability, typified by ecological locking, states that biotas within habitats become integrated into ecological units that, through population and community-level processes, rebound and persist through short-term disturbances. This high frequency community resilience allows the units to persist through geologic time, tracking their preferred habitats during transgressions and regressions. Because species are tightly woven into the fabric of the ecosystem, there is little opportunity for speciation; this also buffers them against extinction. This ecological locking by ecosystem homeostatic processes produces long intervals of regionally stable biofacies in the fossil record. In these models, the primary structuring mechanisms are at the local, community level, controlled by species autecology, species interactions, and local disturbance regime.

The first record of microforaminiferal linings from the early Pennsylvanian of Argentina is presented as consisting of Trochospiral Type I, Planospiral Type II and cf. Uniserial indet. (sensu Stancliffe) forms  while associated with acritarchs, prasinophytes, freshwater algae, spores and pollen grains. Microforaminiferal linings and associated microflora were obtained from the well core YCF.CO3 borehole (interval of 850–851.5 metres below drill floor), which comprises the lower part of the Ordóñez Formation (Chacoparaná Basin). This association documents the development of estuarine or shallow marine environments in the western part of the basin during the Pennsylvanian (Bashkirian?). The origin of these environments was associated with the final phases (transgressions) of the Carboniferous glaciation of Gondwana, documented in the diamictites of the Ordóñez Formation.

Abstract The accuracy of the radiometric ages for the Pennsylvanian-Permian section of the Parana Basin has been progressively increased in the past two decades, allowing a better chronostratigraphic calibration to the related biozones. Most of these new ages are from levels containing spore-pollen associations assigned to the Vittatina costabilis Zone (VcZ), which is revised in detail herein. Unlike previous biostratigraphic proposals, we verified that VcZ is positioned between the Gzhelian and the Artinskian, documenting the Pennsylvanian-Permian transition. A new palynological characterization is proposed for this palynozone, including (i) changes in the definition of its lower and upper limits and (ii) the invalidation of its subzones. Although spores and monosaccate pollen grains are dominant in the VcZ, gymnospermic taeniate bisaccate and polyplicate pollen grains become progressively more abundant up section, representing new plant groups mainly linked to gymnosperms and allied groups. The VcZ documents the first appearance of certain Gondwana taxa of stratigraphic value, such as Converrucosisporites confluens and several species of Vittatina. The stratigraphical distribution of the VcZ is redefined based on previous and unpublished data. In general, the zone is well developed along the basin, but it is better represented between Santa Catarina and Sao Paulo States. No palynostratigraphic changes were consistently observed throughout the palynozone, which is recognized into two lithostratigraphical units of distinct paleoclimatic nature: the upper Itarare Group and the Rio Bonito Formation. Considering that earliest appearance of the Glossopteris in Parana Basin is recorded within the upper Itarare Group from levels bearing palynological associations assigned to the VcZ, a Pennsylvanian age is evidenced for this plant group, which only became dominant across the Gondwana areas in Permian times.

The Late Pennsylvanian Midcontinent Sea (LPMS) of North America, which existed during glacioeustatic highstands of the late Paleozoic ice age, was an immense (>1 × 10 6 km 2) cratonic interior sea exhibiting large-scale estuarine circulation, with a low-salinity surface plume overlying a high-salinity, anoxic, deep water mass. As in river estuaries, these conditions resulted in trapping and recycling of nutrients and organic-reactive elements (e.g., trace metals such as Mo, U, and Zn) in the subpycnoclinal water mass, leading to total organic carbon (TOC) to 40% and peak trace metal enrichment factors (EFs) of 540 (Mo), 73 (U), and 75 (Zn) in the black shale facies of the Hushpuckney Shale. Trace metal EFs increase gradually from distal (Oklahoma) to proximal (Iowa) areas of the Midcontinent Shelf before decreasing abruptly in the Illinois Basin, located to the east of the Mississippi River Arch (MRA). Owing to similar productivity (TOC) and redox (Fe T /Al) proxy values on both sides of this arch, the large differences in trace metal EFs are interpreted to reflect divergent deep-water chemistries; specifically, much larger aqueous trace metal inventories on the Midcontinent Shelf than in the Illinois Basin. This condition implies that (1) deep waters of the Midcontinent Shelf and Illinois Basin were physically separated by the MRA, demonstrating its existence as a positive bathymetric feature during the Late Pennsylvanian, and (2) the saltwater wedge to the west of the MRA functioned as a nutrient trap in which organic-reactive trace metals were strongly concentrated through water-column recycling.

The black shale submember of core shales of Pennsylvanian Kansas-type cyclothems is highly enriched in redox-sensitive trace elements (TEs) relative to the overlying gray shale submember as well as to many other modern and ancient organic-rich deposits. Controls on trace-element behavior in the black shale can be inferred from trace-element enrichment factors (EFs, relative to gray shale) and the relationship of TEs to total organic carbon (TOC). Most TEs conformed to one of two patterns: (1) Mo, U, V, Zn, and Pb exhibited moderate EFs and strong covariation with TOC in samples having < 10 wt.% TOC but large EFs and weak covariation with TOC in samples having >10 wt.% TOC; and (2) Cu, Ni, Cr, and Co exhibited low EFs and moderate to strong covariation with TOC in all samples. These patterns are inferred to represent different responses to benthic redox conditions. The first pattern is characteristic of TEs of ''strong euxinic affinity'', i.e., those taken up in solid solution by Fe-sulfide or involved in other reactions catalyzed by free H 2 S, and resident mainly in authigenic phases, whereas the second pattern is characteristic of TEs of ''weak euxinic affinity'', i.e., those not strongly influenced by the presence of free H 2 S and resident mainly in the organic carbon or detrital fractions of the sediment. These inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples: euxinic conditions were considered to have existed if at least two of four ''redox-indicator'' trace elements (Mo, U, V, Zn) showed euxinic levels of enrichment, and nonsulfidic anoxic conditions were inferred otherwise. The validity of the procedure is indicated by (1) agreement among all four ''redox indicators'' for a large majority of samples (69% of 185); (2) among samples yielding a mixed redox signal, a systematic sequence of TE enrichment (V ! Zn ! Mo ! U); and (3) for TEs of ''weak euxinic affinity'', reduced variance among samples representing each redox facies. Sequential enrichment may be a response to differential redox thresholds for accumulation (e.g., V) or postdepositional remobilization of trace elements (e.g., U) and may provide a basis for finer assessment of redox conditions in low-oxygen paleoenvironments than permitted by simple classification schemes. The multiproxy procedure for redox-facies analysis developed in this study is likely to be more reliable than widely used single-proxy indicators based on trace elements (e.g.

The biogeographic distribution of foraminifers and their belonging to either the southern or northern margins of the Paleo-Tethys are used here for paleogeographic reconstructions of Iran during the Carboniferous. Lower Carboniferous foraminiferal assemblages from northern and central Iran show a cosmopolitan character and affinities to both the southern and northern borders of the Paleo-Tethys. Hence, in the Early Carboniferous Iran occupied an intermediate southern latitude position, forming part of Gondwana. This conclusion is consistent with the Late Ordovician to Early Carboniferous drift history of Iran based on paleomagnetic data. In the Late Carboniferous, the foraminiferal affinities of northern and central Iran with the northern part of Paleo-Tethys suggest that Iran separated from Gondwana and moved northwards to a lower latitude. This separation is also evidenced by the Upper Carboniferous coal-bearing sandstones of the Sardar Formation and sandstones with high degree of...

The Pennsylvanian portion of the Late Paleozoic Ice Age was characterized by stratigraphic repetition of chemical and siliciclastic rocks in the equatorial regions of the Pangean interior. Known as ''cyclothems'', these stratigraphic successions are a 10 5 yr-record of glacial waxing and waning, superimposed on longer term, 10 6 yr intervals of global warming and cooling and a still longer term trend of increasing equatorial aridity. During periods of maximum ice-minimum sea level, the interior craton was widely exposed. Epicontinental landscapes were initially subjected to dry subhumid climate when first exposed, as sea level fell, but transitioned to humid climates and widespread wetlands during maximum lowstands. During interglacials (ice-minima) seasonally dry vegetation predominated. The wetland and seasonally dry biomes were compositionally distinct and had different ecological and evolutionary dynamics.

Kreischeria wiedei Geinitz 1882 (Arachnida: Trigonotarbida) aus dem Oberkarbon (Westfal D) von Zwickau wird im Rahmen vorliegender Studie neu untersucht. Die Familie KreischeriidaeHaase 1890 wird mit einer emendierten Diagnose reinstalliert. Vorläufig werden die ArtenAnzinia thevenini (Pruvost 1919),Gondwanarachne argentinensis Pinto &Hünicken 1980,Hemikreischeria geinitzi (Thévenin 1902),Pseudokreischeria pococki Gill 1924 undPseudokreischeria varia Petrunkevitch 1949 zu den Kreischeriidae gestellt. Kreischeria wiedei Geinitz 1882 (Arachnida: Trigonotarbida) from the Upper Carboniferous (Westphalian D) of Zwickau, Germany is redescribed. The family KreischeriidaeHaase 1890 is reinstated and rediagnosed to accomodate this species. We provisionally refer the speciesAnzinia thevenini (Pruvost 1919),Gondwanarachne argentinensis Pinto &Hünicken 1980,Hemikreischeria geinitzi (Thévenin 1902),Pseudokreischeria pococki Gill 1924 andPseudokreischeria varia Petrunkevitch 1949 to Kreischeriidae too.

Carboniferous coal-forming swamps are an excellent system in which to evaluate the
effects of regional to global climatic changes on ecosystem structure and dynamics.
Stressful physical conditions restrict the access of most species, creating semiclosed
conditions in which the signal-to-noise ratio should be high. We examine patterns of
change in coal-swamp systems during the Pennsylvanian at three levels: landscapes,
habitats within landscapes, and species within habitats. The timing and extent of turnover
at these three levels suggest a hierarchial organization, in the sense that patterns at one
level emerge from interactions among elements at a lower level, and can have subsequent
reciprocal effects on the dynamics at that lower level.
Changes in the species composition of coals, and in the dominance-diversity structure
they define, occur continuously throughout the Pennsylvanian. However, there are distinct
breakpoints that allow us to recognize five basic organizational themes. Bach of these
breakpoints corresponds to an independently inferred change in regional or global climate.
Examination of species-level turnover patterns reveals highest values at the landscapelevel
breakpoints, suggesting at rust that climate change may be affecting species turnover,
which then scales upward directly into landscape changes. Estimation of the
relationship between species turnover and habitat patterns, however, suggests an intermediate
level of organization. Species turnover throughout the Westphalian occurs mostly
within habitats and on strongly ecomorphic themes; species of the same or closely related
and morphologically similar genera tend to replicate each other through time. It is the
proportion of habitats that changes at the landscape-breakpoint boundaries, and habitats
contain the ecomorphic elements that give the landscape its apparent dominance-diversity
structure.
At the Westphalian-Stephanian boundary, high levels of extinction eliminated sufficient
numbers of species that Westphalian ecomorphic patterns were destroyed and a new set of species-habitat dynamics was established. In combination with replacement patterns
during the Westphalian, the extinction suggests that biotic interactions among species
assist in creating a "fabric" or multiniche system that helps constrain the ecomorphic nature
of species replacements, whether such replacements occur through evolution within or
migration into the system. Loss or decline of a species creates a vacant niche, whose limits
are partially defined by the remaining biota. Major disruption of this system by extrinsically
induced extinction permits the system to reestablish the interaction fabric based on
the biologies of the new suite of species.

Evidence of denitrification has been reported from some older marine systems, but it is unclear whether denitrification rates varied during pre-Quaternary glacial cycles. Here we present ratios of organic carbon to nitrogen and nitrogen isotope data from the Upper Carboniferous black shales of the North American mid-continent. In these cyclic deposits, we find evidence of variations in the intensity of denitrification in the eastern tropical Panthalassic Ocean associated with glacially driven sea-level changes. Sedimentary δ 15 N increases during the interval of rapid sea-level rise in each cycle, indicative of intensified denitrification, before returning to background levels as sea level stabilized during the interglacial phase. Nearly identical patterns of denitrification have been observed in the eastern tropical Pacific during the Quaternary period. We therefore conclude that ice ages have produced similar oceanographic conditions and nitrogen cycle dynamics in these regions over the past 300 million years.