Dissertation proposal
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25-09-2015, 09:16 PM
Dissertation proposal
I am trying to figure out a way to upload my dissertation proposal in the event anyone wants to see the complete picture of what I am doing for my doctorate. I don't know if this link will work or not. (I don' think this worked, I will have to find another way to upload it)
If it does, that should allow people to see my proposal (I am in the field this weekend collecting specimens for the Spinatrypa and facies sections)

Being nice is something stupid people do to hedge their bets
-Rick
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25-09-2015, 09:23 PM
RE: Dissertation proposal
I can't get it to upload, so I'll post the text and then the figures in order.

A multi-proxy study of the Late Devonian (Frasnian-Famennian) extinctions in northern Appalachia: geochemistry, sedimentology, stratigraphy, and paleobiology

A Research Proposal, submitted to the faculty of the Center for Integrative Geosciences, University of Connecticut, in partial satisfaction for the requirements of the Ph.D. degree
By
James Andrew Beard
B.S., 2010, University of Tennessee at Chattanooga, Chattanooga, TN
M.S., 2012, Syracuse University, Syracuse, NY

Advisory Committee


(Advisor: Dr. Andrew Bush)

(Co-advisor: Dr. Michael Hren)

(Committee member: Dr. Lisa Park Boush)
Introduction
The Lower and Upper Kellwasser extinction events (LKW and UKW) of the Frasnian-Famennian (F-F) boundary interval in the Late Devonian have received considerable attention over the last three decades, with little consensus on the trigger and kill mechanisms. Multiple hypotheses have been proposed, including bolide impact, sea level change/glacioeustasy, anoxia, eutrophication, ocean acidification, shutdown of the biological pump, climate warming or cooling, and volcanic outgassing (Geldsetzer et al., 1987; Joachimski and Buggisch, 1993; Murphy et al., 2000; Joachimski et al., 2001; McGhee, 2001; Stephens and Sumner, 2003; Bond et al., 2004; Chen et al., 2005; Knoll and Fischer, 2011; Finnegan et al., 2012; Bush and Pruss, 2013; McGhee, 2014). These triggers and kill mechanisms have been used to try and explain the selectivity of these extinctions and their coincidence with carbon and oxygen isotopic anomalies. The organisms that were most adversely affected include the atrypids and strophomenids among brachiopods, shallow water rugosids, and reef-building stromatoporoids (McGhee, 1982; Copper, 1986; Racki, 1998; Copper, 2002).
To gain insight into these global-scale questions, I seek to answer several questions in an understudied region, the northern Appalachians. What is the lateral extent to which these events can be traced out in northern Appalachia (Western New York, Northern and Central Pennsylvania)? How do facies change through the critical intervals spatially and temporally in northern Appalachia? Are the local extinctions and environmental/climatic changes correlative with the global observations? How do these events compare within the Appalachian basin? Can these events be traced into increasingly shallow water in Central/Southern Pennsylvania and West Virginia?
Background
F-F Isotopes: Stable isotopic studies have provided key insights into environmental changes in the F-F interval. Most isotopic studies have focused on δ13Ccarb and δ13Corg and these studies have found two characteristic ~4‰ positive excursions at the base of the LKW and UKW horizons (Joachimski and Buggisch, 1993; Murphy et al., 2000; Joachimski et al., 2001; Joachimski et al., 2002; Stephens and Sumner, 2003; Bond et al., 2004; Brand et al., 2004; Chen et al., 2005; van Geldern et al., 2006; Xu et al., 2012). The proposed triggers for these excursions are varied, as is the interpretation of their relationship to the extinction events, but anoxia is a common theme among them, with some δ34S measurements corroborating the presence anoxia for at least the UKW (Geldsetzer et al., 1987). A more detailed description of some of these studies is included in the following sections, and the values for δ13Corg, δ13Ccarb, and δ18Ocarb are provided in tables 1 and 2.
Carbon (Organic and Inorganic): Both the LKW and UKW event are marked by positive δ13C excursions in the organic and inorganic carbon reservoirs. The magnitude of the excursions is variable depending upon the temporal resolution of the study in question, but a 3-4‰ positive excursion for both the LKW and UKW is typical. The bulk of these studies have focused on more temporally condensed section deposited on carbonate platforms, with particular emphasis on Europe (Joachimski and Buggisch, 1993; Joachimski et al., 2001; Joachimski et al., 2002) and China (Chen et al., 2005; Xu et al., 2012) (Table 1). There are some studies from North America, but the data is more sparse and still not well sampled temporally (Murphy et al., 2000; van Geldern et al., 2006), (Table 1).
Joachimski and Buggisch (1993) focused on a carbonate platform from sites around Europe (Germany, France, Poland, and Austria) and reported a 2.5–3.5‰ positive excursion for the LKW and a 1–3‰ positive excursion for the UKW. Joachimski et al. (2001) returned to one of these sites (Poland) and found within the δ13Corg record for bulk organic matter only a 0.8‰ positive exucrsuon at the LKW and a 3.3‰ postive excursion for the UKW. This latter study also recovered values for organic biomarkers, with ranges from 0 to 0.5‰ for the LKW and 2 to 3.5‰ for the UKW. In general, their resolution of sampling for the LKW was poor, which resulted in a failure to capture the full extent of the LKW excursion. Joachimski et al. (2002) reported δ13Ccarb values from whole rock specimens and recovered a 3‰ and a 2-3‰ positive excursion for the LKW and UKW respecitvely (Germany). Murphy et al. (2000) focused on the deeper-water siliciclastic deposits of Western New York, offshore from my field area, and recovered a ~4‰ positive excursion for the LKW and a ~3.5‰ positive excursion for the UKW. On a carbonate platform in China, Chen et al. (2005) recovered values for the δ13Corg record that show a 1.2-2.6‰ and a 3-3.6‰ positive excursion for the LKW and UKW. The δ13Ccarb record from micritic cements shows only a 0.4-0.8‰ positive excursion for the LKW and a 2.2-2.8‰ positive excursion for the UKW. Xu et al. (2012), also from the same Chinese carbonate platform as Chen et al. (2005), recovered values for δ13Corg at the LKW that shows a 3.1-4‰ positive excursion, and a 3.6-3.7‰ positive excursion for the UKW. Xu et al. (2012) δ13Ccarb records exhibit a 2.1-2.4‰ and 2.1-3.1‰ positive excursion for the LKW and UKW respectviely.
Oxygen: The δ18O record for the LKW and UKW events is more sparse than for δ13C and also exhibits some conflicting information, which may represent diagenetic alteration of some of the reported data (Table 2).
Joachimski and Buggisch (2002) recovered δ18Oapatite values from conodonts within the limestones of Germany that exhibit a 1.2-1.6‰ and 1.0-1.1‰ postive excursion for the LKW and UKW respecitvely, indicating cooling within the LKW and UKW intervals of ~5°C. Values preceding the LKW average ~17.4-17.5‰, and values preceding the UKW (but after the LKW) average ~18.5-19.0‰, suggesting that the post-LKW interval was cooler than pre-LKW (Table 2). Le Houedec et al. (2013) measured δ18Oapatite from conodonts in France and Morroco, recovering a 0.88-1.23‰ positive excursion for the LKW and a 0.51-0.77‰ positive excursion for the UKW (3-5°C), consistient with the cooling from Joachimski and Buggisch (2002). However, Le Houedec et al. (2013) show post-LKW values being more depleted than pre-LKW, indicating that the post-LKW interval was warmer than the pre-LKW interval, (Table 2). Van Geldern et al. (2006) reported δ18Ocarb values from the literature across multiple localities in well-preserved brachiopods. For the interval of interest the localities reported are from Iowa and Manitoba in North America, and Spain, Russia, and China outside of North America. The LKW positve excursion averaged ~0.7‰ and the UKW positive excursion at 0.9‰ (~4°C), with the post-LKW interval also being more depleted than the pre-LKW interval, (Table 2). Chen et al. (2005) report δ18Ocarb values from whole rock specimens, but their data are conflicting, with one site showing depletion within the LKW and UKW intervals, and another site showing enrichment. The values reported in this study are therefore not considered in great detail as they most likely represent at least some degree of diagentic alteration, (Table 2).
Conclusions from the F-F isotope studies: The positive δ13C excursions seen for both the LKW and UKW indicate the sequestration of large quantities of organic matter, which is highly depleted with respect to 12C and therefore leaves the reservoir enriched. Carbon burial and drawdown in CO2 in the LKW and UKW intervals could result in climatic cooling, as indicated by some of the oxygen isotope records that suggest a cooling of 3-5°C (Joachimski and Buggisch, 2002; van Geldern et al., 2006; De Vleeschouwer et al., 2013), but the amount of CO2 drawdown is not well resolved, perhaps as a result elevated pCO2 for the Devonian in general (Berner, 2006; Xu et al., 2012; De Vleeschouwer et al., 2014).
Many authors suggest that anoxia played a major, if not primary, role in the LKW and UKW events (Joachimski and Buggisch, 1993; Murphy et al., 2000; Joachimski et al., 2002; Chen et al., 2005). Some propose the development and spread of anoxia, potentially enhanced through a warming climate or eutrophication (Murphy et al., 2000; De Vleeschouwer et al., 2013) or by weathering of fresh exposures of volcanogenic rock, such as intrusions of basalt emplaced around the same time (Chen et al., 2005). This latter hypothesis is plausible given that recent dates for the Viluy Traps to within the F-F interval (Ricci et al., 2013). There is no data to suggest that the deep ocean was anoxic, leading some researchers to conclude that the anoxia was limited to the shallow epicontinental basins, perhaps providing a deep water refuge for some organisms, like the cooler water rugose corals(Bond et al., 2004).
The majority of these stable isotopic studies have been in temporally condensed sections where the LKW and UKW may be separated stratigraphically by as little as ~2m and up to a maximum of 15-20 m, making it difficult to distinguish short-term events or even fully sample the excursions (Joachimski and Buggisch, 2002; Joachimski et al., 2002; Chen et al., 2005; Xu et al., 2012). These studies have also focused on carbonate platforms with limited macroinvertebrate information included, making it difficult to directly link the isotopic trends to the extinctions and environmental/climatic change within the same study.
Sea Level: Eustasy and sedimentary cycles have been studied various times over the last few decades, but some interpretational differences persist for the intervals bounding the Lower and Upper Kellwasser events (Johnson et al., 1985; Castle, 2000; Filer, 2002). The general agreement for the LKW is a period of transgression coinciding with the beginning of the LKW (approximately the Pipe Creek Shale in the proposed study area), but Johnson et al. (1985) indicates that the transgression is a prolonged event that persists until a regression preceding the UKW. Filer (2002) shows the same transgression coincident with the LKW, but also indicates a period of regression and eustatic fluctuation following it. Both indicate a relatively severe regressive event preceding the transgression coincident with the UKW (roughly coincident with the Dunkirk Shale in the proposed study area). The mechanism driving these eustatic cycles is still contentious. Some have argued that the sea level trends and the extinction events may be directly linked to glacioeustasy, but there exists no evidence of ice coverage at this time (Filer, 2002; McClung et al., 2013; McGhee, 2014). Modeling of orbital and climatic parameters gives at least tentative support to the hypothesis of glacioeustasy, with high elevation regions of polar Gondwana being capable of forming and storing year-round ice, even with elevated atmospheric concentrations of CO2 at ~2180ppm (Berner, 2006; De Vleeschouwer et al., 2014).
Milankovitch cyclicty has also been proposed to explain the lithologic variability, with estimates of ~800 kyr (two 400 kyr eccentricity cycles) separating the LKW from the UKW, and the duration of anoxia during the UKW lasting ~400 kyr (De Vleeschouwer et al., 2012; Da Silva et al., 2013; De Vleeschouwer et al., 2013; De Vleeschouwer and Parnell, 2014; De Vleeschouwer et al., 2014). These studies have focused on Europe for the LKW and UKW events, where interpretation of Milankovitch cyclicty has focused on carbonates. Castle (2000) and McClung et al. (2013) suggested the potential for orbital forcing to play a role in lithologic variation within the Appalachian Basin, but results become more complicated due to tectonic influence as well as disconformities within the sections during periods of subaerial exposure. It is therefore possible that the lithologic variability within my proposed study area represent orbital forcing and/or glacioeustasy, but differentiating between contributing factors may be complicated due to regional effects.
Paleobiology: The LKW and UKW were devastating for the diversity of atrypid and strophomenid brachiopods, atrypids being completely eliminated by the Famennian (Copper, 1986; Rong and Cocks, 1994; Copper, 1998; Racki, 1998). The shallow water rugose corals (Sorauf and Pedder, 1986; Oliver and Pedder, 1994) and ammonoids (for at least the UKW) (House, 2002) also see major losses in biodiversity. The atrypid and strophomenid brachiopods, as well as the rugose corals, are of particular interest because of their abundance in my study area, making it very easy to link changes in lithology and isotopic trends directly to the biostratigraphic record. The cause for these biotic crises remains contentious, with much work on the subject (primarily through geochemistry as discussed in the previous sections) having focused on the role of anoxia. However, some authors (Copper, 1986; McGhee, 2014) proposed that climatic cooling may have played a significant role based on the selectivity of the extinction; taxa that dominated at lower latitudes, and therefore in the warmest water, were preferentially selected for extinction. In the Middle Devonian, the atrypid and strophomenid orders were equally diverse across all latitudes but in the Frasnian both orders were more diverse at the lower latitudes and less diverse at the higher latitudes (Fig. 1), and they were the hardest hit among the brachiopods. In contrast, the brachiopod orders with no latitudinal bias (or better representation at the higher latitudes) were able to weather the F-F and end-Famennian extinctions into the Early Carboniferous (Fig. 1). At the higher latitudes during the Late Devonian, sampling becomes sparser, indicating a need for more and better information to be included into the PBDB through a literature survey. Also noticeably absent from the studies proposing cooling as a trigger, is clear evidence of glaciation, but this may be due to the removal of any glacial deposits associated with the end-Famennian glaciation during the Hangenberg event, or that cooling may not have been severe enough to induce glaciation (McGhee, 2014).

Geologic Setting and Stratigraphy of northern Appalachia
During the Late Devonian, the Appalachian Basin and the Catskill Delta Complex were situated at ~20-40°S, to the northwest of the uplifting Appalachian Mountains during the Acadian phase of orogenesis (Ver Straeten, 2009; Ver Straeten, 2013) (Fig. 2-3). The Catskill complex was a prograding siliciclastic wedge deposited in a foreland basin that thins westward (Fig. 3A), with depositional settings ranging from terrestrial to shallow marine to offshore marine from east to west (Fig. 3B) (Ver Straeten, 2009; Ver Straeten, 2013).
The sediments in my proposed study region of northern Appalachia in New York and Pennsylvania (Fig. 2C) were deposited in a fully marine portion of the Appalachian Basin during the late Frasnian and early Famennian (Pepper and de Witt, 1950a; Streib et al., 1981; Jacobi et al., 1994; Smith and Jacobi, 2001). The transition to terrestrial facies occurs further to the southeast in Pennsylvania during the F-F interval, and terrestrial sediments prograded into the study area later in the Famennian. Terminology for the stratigraphic units in this study varies across the Appalachian Basin, and even within Pennsylvania (Fig. 4 and Tables 3-7). In general the more offshore regions are better defined and studied (e.g., Western New York), with decreasing geochronologic and biostratigraphic information for the more onshore/terrestrially-influenced lithologies in Central Pennsylvania, where marine fossils are rare.
Bush et al. (2015) revised the correlations for late Frasnian and early Famennian formations in the proposed study area. They demonstrated that prior correlations (for instance: Smith and Jacobi, 2001) were incorrect between shallow marine sections in Central New York and offshore sections in Western New York, which were dated previously through conodont biostratigraphy (Over, 1997). Smith and Jacobi (2001), following many previous works, correlated a shale at the top of the Nunda Sandstone with the Pipe Creek Shale, despite the observation that this shale was much thinner and less organic-rich than its westward counterpart. Smith and Jacobi (2001) then correlated the Dunkirk Shale with a thinner shale at the top of the Wiscoy Formation. Bush et al. (2015) showed that these correlations were incorrectusing biostratigraphy, lithostratigraphy, and gamma-ray logs. The true Pipe Creek in central New York was actually the shale that had been previously correlated with the Dunkirk, and a thick organic-rich shale approximately 60 m above the “Dunkirk” of Smith and Jacobi (2001), called the Hume Shale, was actually the Dunkirk Shale. The issues surrounding these miscorrelations existed prior to Smith and Jacobi (2001), and are included in the official geologic map for the state of New York (Pepper and de Witt, 1950b; de Witt, 1993; Roen and De Witt, 2013).
My preliminary δ13Corg records corroborate the findings of Bush et al. (2015) by demonstrating that the timing of the excursion across the shale they defined as the Pipe Creek (LKW) is consistent with the excursion across the Pipe Creek seen in Western New York in Murphy et al. (2000). In Murphy et al. (2000) and in my results, the positive excursion begins at the base of the Pipe Creek Shale. If this shale were the Dunkirk, the excursion would be expected to begin in a thinner shale below the massive organic-rich shale, with the two separated by a coarser interval.

Proposed work
Research questions: Despite the amount of attention that the Kellwasser events have received, several questions persist. What were the primary drivers of extinction? What roles did anoxia, climate change, and eustasy play? Were the mechanisms similar for the LKW and the UKW? What was the timing of environmental/climatic change in relation to faunal turnover? In order to try and address these questions, as well as questions of more proximal interest, I will utilize multiple proxies across several sub-disciplines of geology.
Chapter 1 — Organic Carbon: For the initial phase of this project, I am focusing on bulk δ13Corg records through the LKW and UKW in NY and PA. Some samples were previously collected by Dr. Andrew Bush and colleagues, and I am selecting a subset of these that will provide a higher stratigraphic and temporal resolution than has been published for other studies (Joachimski and Buggisch, 2002; Joachimski et al., 2002; Chen et al., 2005; Xu et al., 2012). To date, four of these localities have been sampled, 1) Cameron, NY (CAM) 2) Tioga, PA (TGB) 3) Tioga, PA (TGA) 4) Big Creek in New York (BCP), with two awaiting initial analysis and one awaiting a duplicate analysis to ensure accuracy (Fig. 2C). Both Kellwasser events should be exposed along Wiscoy Creek, NY, according to Bush et al. (2015), and this section has just been sampled through the critical intervals as of September 2015. This section is particularly important because it is the type section of the Wiscoy Formation and the only section currently hypothesized to contain both the LKW and UKW in the same (relatively) continuous exposure. Three additional sites near Towanda, PA (TF, Laceyville, and Franklindale sections in Fig. 2C) have also been selected for sampling. These new sections will be sampled approximately every 0.5-1 m, with the denser sampling around the hypothesized positions of the extinction events/excursions.
Preliminary Results Chapter 1: Geochemical data for the Lower Kellwasser (LKW) event at the Cameron, NY (CAM) and Tioga, PA (TGB) localities demonstrate the plausibility of recovering primary records from the proposed study area (Fig. 5). At both localities, a ~4‰ positive δ13Corg excursion is recorded coincident with the onset of deposition of the Pipe Creek Shale (approximately the LKW), but the UKW is absent at both localities, which is to be expected given the absence of another organic-rich black shale at the top of each section.
The excursion differs in duration between the two localities. δ13Corg is variable but isotopically light (average of -27.2‰) at the base of the CAM section in the Wiscoy Formation,. The most variability is seen in the nearshore facies, which also houses the most highly depleted values within the coarser beds, perhaps indicative of mixing from isotopically depleted terrestrial input as distance to shoreline decreases. At the base of the Pipe Creek, around 23m, values shift from -27.2‰ to -24.3‰ and reach their maximum value of -23.0‰ at 28.48 m. The average value for the Pipe Creek is -23.0‰ over ~18m of total thickness. The top of the Pipe Creek is placed at the base of the coarse sandstone bed at ~41m where the δ13Corg becomes progressively more depleted, recovering to near pre-excursion values within the lower Hanover equivalent and Canaseraga Formations (average of -25.5‰). Once again, as the nearshore facies begin to return the variability increases towards the top of the section within the Canaseraga at ~85 m. The signal at TGB is similar to what is observed at CAM, but becomes more erratic within the Pipe Creek. In general, the Wiscoy sees variable but light δ13Corg values (average -25.9‰) that become progressively more depleted towards the upper Wiscoy, reaching a minimum near the top of the formation at -27.7‰. The positive excursion here is in the uppermost Wiscoy as the values shift from the minimum at -27.7‰ to -23.4‰. Curiously, the prolonged excursion seen at CAM is not observed at TGB as the isotopic trend recovers to near pre-excursion values within the Pipe Creek (average -26.6‰). The lower Hanover equivalent is variable about an average of -25.9‰ and the Canaseraga is only represented by two samples that average -25.3‰.
Chapter 2 — Carbonate: I will also attempt to measure δ18O and δ13C from well-preserved brachiopods that bound the shales of the LKW and UKW (few specimens are recovered from the shales, and any recovered tend to not retain their original calcitic mineralogy). The δ18O records can provide information on temperature trends associated with the LKW and UKW and/or secular variations in seawater composition, and numerous authors have used well-preserved brachiopod and bivalve shells to reconstruct Paleozoic climates (Rao and Green, 1983; Mii and Grossman, 1994; Veizer et al., 1999; Brand, 2004; Brand et al., 2004; Korte et al., 2005; Frank et al., 2008a; Frank et al., 2008b; Angiolini et al., 2009; Beard et al., 2015). Impunctate brachiopods will be selected if possible, which reduces the influence of cements infilling the shell. Shells must also be well preserved because diagenesis can alter primary isotopic signals. Thin section microscopy and scanning electron microscopy will be used to look for primary shell textures (Cusack et al., 2010). Major, minor, and trace element geochemistry will be used to assess preservation potential; specifically, Fe and Mn tend to be enriched during diagenesis because anoxic diagenetic fluids tend to be enriched in Fe and Mn (Morrison and Brand, 1986; Brand et al., 2003). If possible, a single species will be selected for analysis to minimize interspecies variability. The single species will ideally be abundant and posses a thick secondary layer, as the tertiary (outer) layer is often more depleted as a result of kinetic effects during growth (Cusack et al., 2010).
Chapter 3 — Facies Analysis: A facies analysis will accompany each of the sections sampled for geochemistry in order to assess environmental and/or eustatic change through the intervals of interest (a preliminary facies analysis of the CAM and TGB sections is included in Fig. 5). The inclusion of sedimentological data is intended to facilitate the development of a facies model that will allow reconstruction of local (Appalachian Basin) changes in sea level for comparison with eustatic reconstructions (Filer, 2002; De Vleeschouwer et al., 2013). This record of sea level and environmental change can provide a framework to assess the role of sea level, anoxia, and environmental change relative to the chemostratigraphic and biostratigraphic records. By analyzing facies at numerous sections, I plan to assess environmental change both spatially and temporally and, perhaps, provide an additional chronostratigraphic tool for correlating sections, particularly for the more nearshore sections to the south/southeast where biostratigraphic or chemostratigraphic information is weaker (Towanda and Franklindale in particular).
Facies are broken down into packages of lithologies, defined here as a coherent grouping of lithologies that are >0.25m thick. The facies criteria include: thickness of individual beds within the packages, the alternation of the lithology of beds within the package, and sedimentary structures. The facies being used in my preliminary investigations are based on interpretations by Plint (2010) and include: 1) Shale dominated strata where >80% of the beds are comprised of fissile shales and/or mudstones, perhaps with fine laminations but otherwise few sedimentary structures. Interpreted as offshore/inner-outer shelf. 2) Silty-shales with siltstone interbeds where the silty-shales comprise >50% of the package and the siltstones display hummocky cross-stratification or other evidence of being distal tempestites. Interpreted as lower shoreface-inner shelf transition. 3) Approximately equal contributions of shale/silty-shale, and siltstones with hummocky-cross stratification. Interpreted as lower shoreface. 4) Fine-grained sandstones with minor silty-shale interbeds and hummocky and swaley cross-stratification. Interpreted as lower to middle shoreface transition. 5) Fine-medium grained sandstones with hummocky and swaley cross-stratification and minor silt/mud. Interpreted as middle to upper shoreface. 6) Fine-medium grained sandstones, planar- or cross-bedded. Interpreted as upper shoreface. 7) Fine-medium grained sandstones with long waveform ripples. Interpreted as storm influenced upper shoreface. 8) Pebbly to conglomeratic sandstones with cross-beds, reverse grading, rip-up clasts, silty-shale interbeds, and pebbly oscillation ripples. Interpreted as transgressive shoreface lag deposits (Castle, 2000; McClung et al., 2013).
Preliminary Results Chapter 3: Tioga, PA (TGB): The base of the section begins in the storm-dominated phase of the Wiscoy Formation (facies 3) with a short period of progradation towards middle to lower shoreface (facies 4) that is overlain by a darker shale, the Pipe Creek Shale interpreted as an offshore shale (facies1). At ~11 m in the section is a large cuspate scour in the Pipe Creek (indicated in Fig. 6 by the dashed line), interpreted here as a channel cut that has reworked and mobilized the Pipe Creek further downslope out of the study area. Evidence for this appears in the conglomerate that overlies the Pipe Creek (the lowermost sand of the “Hammond Sandstone”) that exhibits pebbly flute casts preserved in the upper Pipe Creek, (facies 8) and is interpreted as a transgressive lag. The “Hammond Sandstone” above this transgressive lag is cross-bedded, contains shale rip-up clasts (Fig. 7), and is interpreted as lower to middle shoreface (facies 4). It is interbedded with silty shales (facies 2). It is within these silty shales in the “Hammond” that specimens of a Spinatrypa sp. (referred to later as Spinatrypa sp.A) that should go extinct at the LKW are found at this locality, perhaps suggesting that the extinction overlies the Pipe Creek instead of at its base as previously thought. The uppermost pebbly sandstones of the “Hammond” are symmetrically rippled. The lower Hanover equivalent is a storm-dominated facies (facies 3), similar to the upper Wiscoy. The Canaseraga Formation returns to more nearshore facies (facies 4-5) with thicker sandstones that exhibit long waveform symmetric ripples and cross-bedding with a slight reddish tint. The shales interbedded in the Canaseraga are still a bit of an enigma, as they do not resemble other shales from the proposed study area; they tend to have a reddish tint and foundered sandstone balls within them. At present, these shales are labeled as “facies 1” but most likely do not represent a similar depositional setting compared to the Pipe Creek, and are perhaps a more nearshore shale deposit (lagoonal or estuarine?).
Cameron, NY (CAM): The base of the Wiscoy starts stratigraphically further down than at TGB in the nearshore facies (facies 3.5-4). These nearshore facies give way to the storm dominated facies (facies 3 then 2) before onset of deposition of the Pipe Creek (facies 1). The Pipe Creek is approximately double the thickness at CAM compared to TGB (~11.5m at Tioga compared to ~18 m at CAM), providing at least tentative support for the removal of some of the Pipe Creek at TGB. It is worth noting that the apparent extinction for the LKW occurs before the onset of Pipe Creek deposition at this locality, but this may reflect the Signor-Lipps effect whereby the Wiscoy Fauna persists stratigraphically further than we were able to successfully sample. Thinner siltstone layers periodically interrupt the Pipe Creek facies as the shale transitions from black to grey (facies 2). The Pipe Creek briefly returns to thicker siltstones/silty shales towards the top that are truncated by a sharp contact between the last shale of the Pipe Creek and the overlying sandstone of the lower Hanover equivalent, representing a transition from facies 3 to 4. The lower Hanover equivalent returns to a similar depositional system as the upper Wiscoy (facies 2-3) with storm-dominated interbedded silts, shales, and sands. The Canaseraga is reminiscent of the nearshore facies seen at the base of the section in the Wiscoy and the Canaseraga at TGB (facies 3-4).
Chapter 4 — Spinatrypa species identification: In the Wiscoy Formation in the southern/central New York region of the study area, there are multiple (2-3) morphologically distinct specimens of Spinatrypa that have traditionally been lumped into the species Spinatrypa hystrix (Hall, 1843) or misidentified. The type specimens of S. hystrix are exterior molds housed at the American Museum of Natural History in New York City that preserve remnants of the spines but do not show much of the three-dimensional structure, such as the existence or prominence of a fold or sulcus. It is therefore possible that one of the Wiscoy species is S. hystirx. Examination of the type specimens will be sought for comparison. These species of Spinatrypa all apparently go extinct at the LKW event with a new species originating after the LKW but that then goes extinct at the UKW (S. planosulcata). It is therefore an important component of my research to better understand these species and properly define the ways in which they can be distinguished from one another, especially in order to make comparisons with extinctions outside the basin and within my study area.
Preliminary results Chapter 4: The first of the potential species is a larger form (Spinatrypa sp. A, ~35 mm in length and ~37 mm wide, Table 8 and Figure 8) whose length to width ratio is nearly 1 and occurs in muddy-silty substrates in interbedded within the “Hammond” overlying the Pipe Creek Shale. The specimen is often flattened post-mortem, but demonstrates the presence of a minor sulcus at the edge of the ventral valve. The dorsal valve appears to exhibit a minor fold and a strongly convex shape (but this may reflect post-mortem compression of the shell as the most highly curved specimen has a L/W >1). The ventral valve is convex near the umbo but begins to flatten out towards the extremities of the shell. The shell is lamellose with strong growth banding and approximately 10-11 costae that are coarsely spaced. No other species at this time seems to exhibit these characteristics (Stainbrook, 1945a; Cooper and Dutro, 1982), so this may be a new species.
A second morphological variant (Spinatrypa sp. B, Fig. 9) is typically smaller (~21 mm in length and ~25 mm wide) with a nearly equal length to width ratio (~0.83), (Table 9 and Figure 9). The shell is uniplicate or may exhibit a moderate fold and sulcus with a convex dorsal valve, a weakly convex ventral valve, and its maximum width near the median of the shell, away from the hinge. The fold is defined by 2-3 costae; the costae split very near the hinge and extend to the edge of the shell. The sulcus is defined by 1-2 costae that extend from the hinge to the edge of the shell, flanked by 2 costae on the edge of the sulcus. This specimen is similar to that of a New Mexican species, S. compacta (Cooper and Dutro, 1982), but may be Hall’s S. hystrix.
The third potential species (Spinatrypa sp. C, Table 10, Fig. 10) is very similar to Spinatrypa sp. B in size (20 mm in length and 27 mm wide) but its L/W ratio and its shape is slightly different (0.75 L/W and more elongate along its width), and exhibits a stronger fold than S. sp. B. The dorsal fold is also defined by 2-3 costae with the central costae (if present) being less prominent than the two flanking it and may cause the fold to be sulcated, and a prominent sulcus on the ventral valve defined by 1-2 costae, if 2 they split from 1 very near the umbo. The fold is very pronounced with near vertical edges of the sulcus and a strong arch within the fold, shown with the red dashed lines in Fig. 10 G and H. This specimen also has well-defined cardinal extremities that define the maximum width of the shell near the hinge if preserved. This species is similar to specimens described as variants of the Iowan species, S. trulla and S. trulla decorticata, but may be morphologically distinct enough to warrant a new species assignment (Stainbrook, 1945b; Cooper and Dutro, 1982).

Significance of the Study
In order to fully understand the impacts and implications of major biodiversity losses through time, better resolution is needed in order to differentiate between correlations and causations within the rock record. The F-F is one such event where the correlation of organic-rich shales and limestones associated with anoxia at both the LKW and UKW extinction horizons is purported to be causal. The correlation of anoxic deposition with the timing of the LKW and UKW extinctions may not be causally linked however, as proposed by some (Joachimski and Buggisch, 1993; Murphy et al., 2000; Joachimski et al., 2002; Chen et al., 2005; Xu et al., 2012; De Vleeschouwer et al., 2013), and some of the original hypotheses, (such as: Copper, 1986), suggesting climatic cooling may make more sense given the selectivity of the extinctions as well as our latest sampling within the horizon immediately overlying the anoxic shale of the Pipe Creek at the Tioga, PA section (TGB).
Without attributing the extinction events to the correct mechanism(s), every assessment that follows is suspect. For instance, given the selectivity of the extinction, why did the brachiopods, the atrypids and strophomenids in particular (Copper, 1986; Rong and Cocks, 1994; Copper, 1998; Racki, 1998), and shallow water rugose corals (Sorauf and Pedder, 1986; Oliver and Pedder, 1994) suffer the greatest losses at the LKW with the ammonoids showing no apparent extinction at the LKW but an extinction at the UKW (House, 1985; House, 2002) (along with the remaining atrypids)? If we infer that anoxia is the primary driver of extinction, then we would necessarily conclude that it is these groups that were the most sensitive to changes in [O2]. But this does not explain any of the other observed trends or counter evidence, such as the apparent selectivity of the extinctions with latitude such that low latitude faunas suffered the greatest biodiversity losses (Fig. 1). Was anoxia somehow more pronounced at the lower latitudes? Did anoxia only develop within the low latitude epicontinental basins, leaving the deep ocean well oxygenated? How does one provide a mechanism for the development and spread of anoxia that is restricted to only a certain set of limiting conditions that mirrors an apparent selection against warm-adapted species? This also contradicts studies, like those of Boyer and Droser (2009) that show that some brachiopod species are tolerant of low-O2 conditions and that settings in epicontinental basins would rarely have been fully anoxic. So, how does one use anoxia as the primary driver of extinction when anoxia would have been short-lived in favor of dysoxia, the groups most adversely affected were more tolerant of dysoxic conditions, and when selective signatures suggest cold-adapted species faired better than warm-adapted species?
It seems more likely that the spread and development of anoxic/dysoxic settings in the epicontinental basins was not a primary driver of extinction, but perhaps played a supporting role in the suppression of origination rates or recovery. Climatic change seems more likely as the primary extinction driver, with the onset of cooling selecting against warm-adapted (low latitude dominant) species. The δ13C record provides support for the mechanism driving this climatic cooling where the positive excursion represents burial of organic matter, thus reducing atmospheric pCO2, facilitating a drawdown in a major greenhouse gas and resulting in a cooling event of 4-5°C (De Vleeschouwer et al., 2014).
Important impications for proposed work: 1) The ability to better resolve timing and mechanisms directly related to the extinction events. 2) A more thorough analysis using multiple proxies for environmental and climatic change, coupled to a temporally expanded study area that has the ability to provide some much needed clarity about the F-F extinction events. 3) Better analysis and identification of Spinatrypa species through the critical interval, including the resolution of taxonomic uncertainties that have persisted for over a century.

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25-09-2015, 09:27 PM
RE: Dissertation proposal
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25-09-2015, 09:36 PM
RE: Dissertation proposal
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I have run out of space for attachments No so I can't post the pictures of species C or the tables.

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26-09-2015, 02:42 AM
RE: Dissertation proposal
Get em out of there and use imgur. Wink

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26-09-2015, 08:43 PM
RE: Dissertation proposal
What, no Table of Contents? Laugh out load I would hate to put mine on here, it's 185 pages. Yuck.

"If we are honest—and scientists have to be—we must admit that religion is a jumble of false assertions, with no basis in reality.
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27-09-2015, 06:08 AM
Dissertation proposal
(26-09-2015 08:43 PM)The Organic Chemist Wrote:  What, no Table of Contents? Laugh out load I would hate to put mine on here, it's 185 pages. Yuck.

Organic chemistry would be a bit longer, but the proposal doesn't have to have a T of C in this case. It's set up more like a journal submission.

My dissertation will have to have a T of C though.

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29-09-2015, 07:16 AM
RE: Dissertation proposal
(27-09-2015 06:08 AM)TheBeardedDude Wrote:  
(26-09-2015 08:43 PM)The Organic Chemist Wrote:  What, no Table of Contents? Laugh out load I would hate to put mine on here, it's 185 pages. Yuck.

Organic chemistry would be a bit longer, but the proposal doesn't have to have a T of C in this case. It's set up more like a journal submission.

My dissertation will have to have a T of C though.

I was just giving you a hard time. Big Grin

"If we are honest—and scientists have to be—we must admit that religion is a jumble of false assertions, with no basis in reality.
The very idea of God is a product of the human imagination."
- Paul Dirac
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29-09-2015, 10:23 PM (This post was last modified: 29-09-2015 10:30 PM by Ted Tucker.)
RE: Dissertation proposal
BD,best of luck with your dissertation proposal! You are now published in the Journal of the T.A.

Evolutionary Science and Geology are two of my favorite subjects, as the amateur armchair scientist enthusiast that I am. I just can't seem to read fast enough to keep up. I just finished a course in Geology from the American Museum of Natural History. Something about the deep geological time and platonic movement as it ties to the evolutionary history of life leaves me with awe.

I look forward to reading the outcome of your research.

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." -Albert Einstein
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