Paleopedology of the Late Triassic Middle Passaic Formation, Newark Supergroup, Pottstown, Pa

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PALEOPEDOLOGY OF THE LATE TRIASSIC MIDDLE PASSAIC FORMATION, NEWARK SUPERGROUP, POTTSTOWN, PA

A Thesis Submitted to the Temple University Graduate Board

In Partial Fulfillment Of the Requirements for the Degree Master of Science

By Steven Booty August 2013

______Dr. Dennis O. Terry, Jr., Advisor

______Dr. Allison R. Tumarkin-Deratzian

______Dr. David E. Grandstaff ABSTRACT

Cyclic stratigraphy has been recognized in the Newark Basin for many years.

Each package, referred to as a Van Houten Cycle (VHC), generally has three divisions: shallow lake, deep lake, and subaerial exposure. Van Houten (1964) first proposed that

Milankovitch orbital forcing was responsible for the manifestation of these ~21 kyr cycles. Although root traces have been observed in VHCs by others, no detailed paleopedological analysis has been performed that examines the relationship between individual VHCs, orbital forcing, and paleosol development.

The Middle Passaic Formation of Late Triassic age is continuously exposed for over 30 meters along a railroad cut that follows Manatawny Creek near Pottstown, PA.

Six VHCs were identified at this location and the upper most three were selected for detailed study due to their strong development. Three Van Houten Groups (VHGs), consisting of VHC Division 3, Division 1, and Division 2 respectively, were formed in order to group paleosol profiles (Division 3) with stratigraphically adjacent lacustrine units (Divisions 1 and 2) since the lakes directly affect the paleosurface through inundation and erosion.

Petrographic analysis suggests that soils in this section only developed to the degree of Entisols or Protosols. Voids are lined with chalcedony and cored with calcite indicating diagenetic alteration. Molecular weathering ratio calculations proved unreliable due to diagenetic alteration of the strata. Magnetic susceptibility was measured on two intervals of the section, but is not well-suited to fractured, massive rock due to signal attenuation.

Paleosol development is greater in instances where the overlying lake is poorly developed. Paleosols that are associated with a shallow lake or no lake likely have more time to develop than paleosols associated with deep lakes as the precipitation filling the lake would saturate the soil, hindering pedogenesis. The VHCs’ ~21 kyr interval forces time to be the limiting factor for pedogenesis in this section, ending in either sedimentation or inundation. However, time is also tied to climate as it modulates from relatively moist to relatively drier within a VHC. Orbital forcing is the ultimate controlling factor in soil formation since time, climate, insolation, and precipitation are all interrelated and influenced by it. Relief is independent of orbital forcing and a possible control on soil formation within the Basin. Soils that formed distal from the bounding fault may not have been subject to inundation due to their higher elevation.

Further research is needed to establish paleocatenary relationships of soil within the

Newark Basin.

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ACKNOWLEDGMENTS

There are a lot of thanks to give regarding this project. Some people may require their own page, but I’ll try to paraphrase.

Thanks to the Colebrookedale Railroad, especially Beanie, for allowing us on their land.

I would like to thank all the professors for pushing me to make observations, not interpretations. DT, thank you for showing me the wonderful world of paleopedology and getting me started with fieldwork… and this project. It was puns of fun being your advisee. May the peanut butter joke forever live in infamy. G, when you weren’t making fun of New Jersey I suppose you may have taught me a thing or two about isotopes.

Your straightforward advice was always worth the “Well, no…” that surely followed whatever question I had. But I got there! Allison… kitty! Also thank you for providing me background information for this project and helping me (and the rest of us) teach fossils to the evolutions kids. And sarcasm is cool or whatever.

To my fellow graduate students: I literally could not have done this without you.

Andrew, Joe, and Justin, you were all there from day one, dealing with herp, derp, kee, and other things I say that make no sense. Good on you guys, good on you. Thanks to

Logan, your curiosity is surpassed by no one else I know. Keep on Logan-ing! Thanks to the chemistry kids: especially Mongo and Kate – always making sure I’m not hearing colors. Thanks to Nick for being a dog. Here is where I would thank Oest. Thank you

Jesse for making this awkward and thanks to Stevie Pee and Dr. Myer for all the XRD help. Bill, thank you for being my ped-head mentor over these past two years. You’ve helped me with my thesis more than these three sentences could possibly cover.

Prrrrrrrttttttttt...

I must give an extra special thanks to Shelah for making sure everything went as smooth as CST administrative malarkey would allow, and for always keeping the coffee pot full.

Also thanks to Jim and Donald for keeping the department together.

Thanks to the undergraduates that helped me with this project, either directly or indirectly. Danni, thanks for making thin sections like a boss. Leslee, tank you for keeping me from freaking out, and helping out when you could. Supreme thanks to Matt

Enos for helping me with my field work, even when it was on weekends or got boring.

Last, but not least, I want to thank my family for understanding/putting up with my decision to further my education and for their support.

TABLE OF CONTENTS

Page ABSTRACT ………………………………………………………………………. ii ACKNOWLEDGMENTS ...……………………………………………………….. iv LIST OF FIGURES ………………………………………………………………... viii LIST OF TABLES …………....…………………………………………………… x

CHAPTER 1. INTRODUCTION …………………………………………………………….. 1

2. BACKGROUND ……………………………………………………………… 8 2.1 Field Site ………………………………………………………………. 8 2.2 Background Geology ………………………………………………….. 8 2.3 Previous Work ………………………………………………………… 14 2.3.1 Newark Basin ……………………………………………….. 14 2.3.2 Paleosols …………………………………………………………….. 19

3. METHODS ……………………………………………………………………. 22 3.1 Field Work ……………………………………………………………. 22 3.1.1 Paleopedological Analysis ………………………………….. 22 3.1.2 Magnetic Susceptibility …………………………………….. 23 3.2 Laboratory Analysis …………………………………………………... 23 3.2.1 Depth Ranks ………………………………………………… 23 3.2.2 Soil Micromorphology ……………………………………… 23 3.2.3 Clay Mineralogy …………………………………………….. 24 3.2.4 X-Ray Fluorescence ………………………………………… 24

4. RESULTS ……………………………………………………………………... 26 4.1 Lower Van Houten Group …………………………………………….. 26 4.2 Middle Van Houten Group ……………………………………………. 31 4.3 Upper Van Houten Group …………………………………………….. 34 4.4 Clay Mineralogy ………………………………………………………. 35 4.5 Molecular Weathering Ratios …………………………………………. 38

5. DISCUSSION …………………………………………………………………. 47 5.1 Agents of Soil Formation ……………………………………………... 47 5.1.1 Climate ……………………………………………………… 47 5.1.2 Organisms …………………………………………………… 48 5.1.3 Parent Material ……………………………………………… 50 5.1.4 Relief ………………………………………………………... 51 5.1.5 Time …………………………………………………………. 53

5.2 Molecular Weathering Ratios …………………………………………. 54 5.3 Magnetic Susceptibility ……………………………………………….. 54 5.4 Diagenesis ……………………………………………………………... 55 5.5 Lake Facies and Marl Units ……………………………………………. 57 5.6 Orbital Forcing ………………………………………………………... 61 5.7 Modern-Day Comparisons ……………………………………………. 64 5.8 Implications …………………………………………………………… 65

6. CONCLUSIONS ……………………………………………………………… 67

REFERENCES CITED ……………………………………………………...... 69

APPENDICES Appendix A. X-Ray Fluorescence Instrument Error Based On Bhvo Analyses …………………………………………………………………... 76 Appendix B. Composition Of Samples From Paleosols And Lacustrine Sediments In Weight Percent Of Oxides And Minor Elements (ppm)……. 77 Appendix C Magnetic Susceptibility Data ………………………………… 79

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LIST OF FIGURES

Page

Fig. 1 – Geologic map of the Newark Basin……………………………………….. 2

Fig. 2 – Comparison of Triassic and modern day rift basins in Eastern Africa……. 3

Fig. 3 – The Van Houten Cycle model……………………………………………... 5

Fig. 4 – Exposures of various Triassic facies in the Newark Basin………………... 6

Fig. 5 – Aerial view of Pottstown, PA……………………………………………… 9

Fig. 6 – The Newark Basin as it was in the Late Triassic and today……………….. 11

Fig. 7 – Drill core data from the Newark Basin Coring Project……………………. 12

Fig. 8 – Cartoon representation of the three basic Milankovitch cycles…………… 17

Fig. 9 – Graphical representation of the hierarchy of sedimentary cycles…………. 18

Fig. 10 – Cross section of the Newark Basin Coring Project………………………. 20

Fig. 11 – Measured section of the exposure at Pottstown, PA…………………….. 27

Fig. 12 – Van Houten Cycle-scale measured section of the exposure at Pottstown.. 28

Fig. 13 – Photomicrographs of Unit 16…………………………………………….. 32

Fig. 14 – Photomicrographs of Unit 17…………………………………………….. 33

Fig. 15 – Photograph of Unit 19 and photomicrograph of clay fabric…………… 36

Fig. 16 – Photomicrographs of features within Unit 19……………………………. 37

Fig. 17 – Photomicrographs of Unit 20 and polished slabs from Units 29 and 30… 39

Fig. 18 – Photographs of various units within the middle Van Houten Cycle……... 40

Fig. 19 –.Photographs and photomicrographs of Unit 28………………………….. 41

Fig. 20 – Photomicrographs of Unit 30…………………………………………….. 42

Fig. 21 – X-Ray diffractogram of profiles………………………………………….. 43

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Fig. 22 – Molecular weathering ratios of each of the selected paleosols…………... 44

Fig. 23 – Bioturbation features within the study section…………………………… 49

Fig. 24 – Schematic drawings of the various basin types…………………………... 52

Fig. 25 – Photomicrographs of Unit 21…………………………………………….. 60

Fig. 26 – Photomicrographs of Unit 30…………………………………………….. 62

LIST OF TABLES

Page

Table 1 – Depth Ranks …………………………………………………………… 23

Table 2 – Description of Units …………………………………………………… 30

Table 3 – Molecular Weathering Ratios …………………………………………. 45

CHAPTER 1

INTRODUCTION

Divergent tectonics during the Late Triassic led to the formation of a series of rift basins stretching hundreds of kilometers along the East Coast of North America and the

West Coast of Africa (Smoot, 1991; Schlische, 1993; Olsen and Kent, 1996; El-Tabakh and Schreiber, 1998; El-Tabakh et al., 1997). The Proto-Appalachian Mountains shed much of their sediment into these basins and into the Atlantic Basin over tens of millions of years (Smoot and Olsen, 1988; Smoot, 1991), creating a sequence of strata that provides one of the longest, and most detailed records of continental climate change in the world (Arguden and Rodolfo, 1986; Olsen et al., 1996). At approximately 7,000 meters in thickness, the Newark Basin is the thickest of the exposed Triassic half grabens and is consequently the most studied of all the Early Mesozoic basins (Fig. 1; Arguden and Rodolfo, 1986; Schlische, 1992, 1993; Olsen et al., 1996). Modern analogues for these depositional environments can be seen in the East African Rift Valleys as they are of similar size and shape (Fig. 2; Olsen, 1986a; Smoot and Olsen, 1988; Schlische, 1993;

Whiteside et al., 2011; Harris et al., 2013).

McLaughlin (1933) was the first to document the cyclic nature of lacustrine sediments in the Newark Basin, and Van Houten (1964) was the first to hypothesize that cyclic lacustrine and mudstone deposition in the strata of the Hartford Rift Basin, CT, which is a northern analogue to the Newark Basin, was due to orbital forcing. These cycles were recognized in the Newark Basin several decades later by Olsen (1985), who termed them “Van Houten Cycles” (VHCs, Figs. 3, 4a). Olsen (1986a) quantified these cycles using Fourier analysis, providing further evidence that VHCs are the physical

Figure , New City York Fault (R). Boxed shown area in oximate location Pottstown, of dot) PA (green

. Note the Jacksonwald syncline (J) theand Ramapo (1996).

et al. et

– Geologic map the Newarkof Basin indicating appr Modified from Olsen

. Figure 1 indicated (NYC) by yellow dot 5

Figure 2 - Comparison of Triassic and modern day rift basins. Seismic reflections were used to define strata most likely to be preserved. Insert shows map of East African Rift lakes Turkana (Tu), Albert (A), Victoria (V), Tanganyika (T), and Malawi (M). From Whiteside et al. (2011).

3 manifestation of the ~21 kyr cycle of Milutin Milankovitch’s theory of astronomically induced climate change as Van Houten (1964) proposed (Schlische, 1992). These cycles vary in their degree of development throughout the basin over geologic time (Olsen and

Kent, 1996). Although these cycles have been studied extensively throughout the

Newark and Hartford Basins for over 80 years (McLaughlin, 1933; Van Houten, 1964;

Olsen, 1985, 1986a, 1986b, Smoot, 1991; Wolela and Gierlowski-Kordesch, 2007;

Gierlowski-Kordesch, 1998), paleosols have remained virtually unstudied or ignored

(Smoot and Olsen, 1988; contra Schaller et al., 2011, 2012).

Paleosols of the Newark Basin represent an as yet untapped source of paleoclimatic and paleoenvironmental data. Soils need subaerial exposure, sufficient moisture and time to differentiate the substrate in order to form distinct horizons

(Birkeland, 1999). Paleosol profiles with distinct root traces are observed stratigraphically below deep lacustrine beds at this exposure. The purpose of this study is to test the hypothesis that the relative degree of ancient soil formation is greater in well- expressed VHCs (i.e. having distinct shallow and deep lake divisions) within the Middle

Passaic Formation of the Newark Supergroup. If this hypothesis is true, then well- developed paleosols will be found associated with deep lake beds and poorly developed paleosols will be associated with shallow lake beds or no lake, suggesting that climate controls the degree of pedogenesis. If this hypothesis is not true, then time, as a function of orbital forcing, should be the limiting factor in soil formation.

subaerial t a tsingle a Van Houten -stand, division and lake 3 records level fall and in the Newark Basin. Divisionsrepresen 1 through 3 n lake2 records high . - Typological - classification level lake of cycles 3

Figure Cycle. Division 1 records divisiolevel rise, lake (Fromexposure Olsen and Kent, 1996)

Figure 4 – Exposures of various Triassic facies in the Newark Basin. Cyan arrows indicate up direction. (A) View of a Van Houten Cycle at Pottstown, PA . Divisions are marked in yellow. ( B) Fanglomerate proximal to the bounding fault of the Newark Basin near Reading, PA. ( C) Cross bedding in a channel sandstone, Stockton Formation, at Phoenixville, PA. Scale in cm and inches. ( D) Mudstone at Pottstown, PA (between yellow lines). Note the massive portion (m) closer to the top of the unit. Red scale bar is approximately 25 cm. ( E) Mudstone at Pottstown, PA (yellow line and above). Notice the more massive section (m) surrounded by more fractured material above and below (f). Red scale bar is approximately 50 cm. ( F) Algal laminations at Pottstown, PA, just above a massive layer. Pencil for scale.

CHAPTER 2

BACKGROUND

2.1 Field Site

This site is located close to the middle of the basin with the bounding fault to the northwest and basin hinge to the southeast (Fig. 1). Due to the mechanics of half graben development, the depositional environments change from fluvial (such as in Phoenixville,

PA, Fig. 4c), to lacustrine, to predominately subaerially exposed. The study site is located along an abandoned railroad cut in Pottstown, Pennsylvania (Fig. 5), just north of

Manatawny Park, and trends for almost 400 m along Manatawny Creek (starting at

40.262368, -75.661383). Strata are gently dipping (~15º) to the northwest and consist of four lithologies: mudstone, sandstone, marlstone and infrequent carbonates. Mudstones are massive, usually thicker than 4 meters, and contain occasional ‘pencil’ fractures that trend N54W. Sandstones consist of fine sand, are massive, and occur approximately every 4-7 meters in the lower part of the exposure. The marlstones are massive, composed of a high percentage of carbonate, and occur stratigraphically above mudstones. Relatively thin (~1 m) layers with fine (0.5-3 mm) laminations and darker hue are largely composed of carbonate (Olsen, 1986a, 1990, 1998).

2.2 Background Geology

The Newark Basin is part of a system of half-grabens, extending from

Newfoundland to North Carolina (Fig. 6), which resulted from the reactivation of

Precambrian and Paleozoic thrust faults as normal faults (Smoot and Olsen, 1988, 1994;

Schlische, 1992; Gierlowski-Kordesch, 1998). These basins represent a failed rift system which began in the Early Triassic with the opening of the Atlantic Ocean Basin. The

arth, Julyarth, 2013. . Study site oval.indicated by From red Google E Figure 1 – Aerial view – Aerial of Pottstown, PA from

Figure 5 9

Newark Basin is bound to the northwest by the Ramapo Fault. To the southeast, it is bordered by Cretaceous strata, except in Pennsylvania where it is bordered by Paleozoic rocks (Smoot, 1991; Schlische, 1992, 1993; Olsen et al., 1996). Not only is the Newark

Basin the largest of the basins, it is also the deepest, at over 7,000 meters of sediment in some places (Arguden and Rodolfo, 1986; Smoot, 1991; Schlische, 1993; Whiteside et al., 2011), with some estimates as high as 10,000 meters (Arguden and Rodolfo, 1986).

The Triassic Newark Basin is comprised of the Stockton, Lockatong, and Passaic

Formations, which formed during different stages of basin evolution (Figs. 4a, b, c and 7;

Arguden and Rodolfo, 1986; Olsen, 1986b; Schlische and Olsen, 1990; Olsen et al.,

1996; Olsen and Kent, 1996; Schlische, 1993). The Stockton Formation is composed of conglomerates and alluvial fans which are arkosic in composition with occasional, thin mudstones (Arguden and Rodolfo, 1986; Smoot and Olsen, 1994; Gierlowski-Kordesch and Park, 2004). The Lockatong Formation is composed of predominantly layers of black, gray, bluish-purple, and green shale between 3 and 7 meters thick. The Passaic

Formation consists mostly of red mudstone with distinct, laterally continuous dark shale beds of various thickness and fabric (Smoot and Olsen, 1988, 1994). The Stockton

Formation records fluvial deposition resulting in excess sedimentation relative to the

Basin’s capacity while the Lockatong Formation records a period of deep, perennial lakes, representing a sediment-starved system (Schlische, 1993; El-Tabakh et al., 1997).

The Passaic Formation is the thickest unit in the Newark Basin, thicker than the Stockton and Lockatong Formations combined, and represents a period of increased accommodation space relative to sediment input with shallow (relative to the Lockatong

Formation), playa lakes (Schlische, 1993; Olsen and Kent, 1996; Olsen et al., 1996;

Figure 6 – The Newark Basin as it was in the Late Triassic, and today. From Olsen and Kent (1996).

Figure 7 – Drill core data from the Newark Basin Coring Project. Modified from Olsen et al. (1996). Arrow shows approximate stratigraphic position of study site.

Gierlowski-Kordesch, 1998; Gierlowski-Kordesch and Park, 2004). Some of these formations have temporal analogues in other basins. For example, the New Haven

Arkose in the Hartford Basin is the temporal equivalent to the Passaic Formation

(Gierlowski-Kordesch, 1998; Gierlowski-Kordesch and Park, 2004).

The Lockatong and Passaic Formations record the best evidence of ~21 kyr periods (Van Houten Cycles) of time as stratigraphically varying facies (Van Houten,

1962, 1964; Olsen, 1986a; Olsen et al., 1989). These cycles represent the precession of the equinoxes (wobble) as described by Milankovitch theory and have been observed in the rock record for over 80 years (Fig. 8a, McLaughlin, 1933; Van Houten, 1962, 1964;

Olsen, 1986a; Olsen and Kent, 1996; Olsen et al., 1996). The two other orbital cycles include obliquity (angle between the equatorial and ecliptic planes, Fig. 8b), ranging from

22.1° to 24.5°, at ~41 kyr intervals, and eccentricity (roundness of Earth’s orbit), ranging from near 0 to 0.06, at ~100 kyr intervals (Fig. 8c, Hayes et al., 1976). Higher order stratigraphic cycles have been identified in Newark Basin strata and include the short modulating cycle (109 kyr, Fig. 8c), McLaughlin Cycle (405 kyr), and the long modulating cycle (1.75 my, Olsen et al., 1996, 2010; Olsen and Kent, 1999, Fig. 9).

Perturbations in Earth’s orbit affect the time-averaged amount of insolation

(amount of net solar input) received by Earth’s surface which, in turn, affects the rate of evaporation and precipitation (Hayes et al., 1976; Olsen et al., 1989). The high order orbital cycles (i.e. obliquity, eccentricity, Fig. 8) interfere with the short-term precessional cycle by enhancing or diminishing its effect on insolation, thus resulting in the manifestations of stratigraphic cycles (short modulating, McLaughlin, and long modulating cycles, Fig. 9). The balance of precipitation vs. evaporation (input vs. output)

13 is one of the determining factors on lateral facies changes and, therefore, lake formation

(Olsen, 1986a; Olsen et al., 1989). Other factors controlling lake formation/depth (to be discussed later) include subsidence rate, orographics, accommodation space, proximity to bounding fault (location in basin), and inter-basinal tectonics (Olsen, 1986a; Schlische,

1992, 1993).

2.3 Previous Work

2.3.1 Newark Basin

From late 1990 to early 1993 Olsen and Kent headed the Newark Basin Coring

Project (NBCP). The goal of this project was to recover the entirety of the Triassic section from the basin. Drilling one deep core was deemed too risky due to the presence of faults at depth. However, the five northeast-dipping fault blocks in the Newark Basin provide significant offset and allowed the drilling of several cores over a great horizontal distance. To ensure stratigraphic correlation, each core overlaps adjacent cores by an average of 25 percent. Through the NBCP (Fig. 10) Olsen and Kent (1996) showed that

VHCs have a periodicity of ~21 kyr. Various researchers have interpreted these cycles as a result of Milankovitch-forced climate change (Van Houten, 1964; Olsen, 1986a, 1986b;

Smoot and Olsen, 1988; Olsen and Kent, 1996). Generally, each of these packages consists of a shallow lacustrine unit, a deep lacustrine unit, and a terrestrial unit (Smoot and Olsen, 1994; Olsen and Kent, 1996). The shallow lacustrine unit (Fig. 3, division 1) has been interpreted as a relatively moist climate and the deeper lacustrine unit (Fig. 3, division 2) has been interpreted as lake highstand and the peak of each VHC. The upper terrestrial unit (Fig. 3, division 3) has been interpreted as relatively drier conditions, possibly resulting in subaerial exposure (Olsen, 1986a).

Lacustrine carbonate is formed under specific climatic and sedimentological conditions, ranging from tropical to glacial, with little to no siliciclastic influence

(Prothero and Schwab, 2004; Gierlowski-Kordesch, 2010). Carbonate formation is common in two distinct environments: tropical humid (e.g. Bahamas) and tropical arid

(e.g. Persian Gulf). Carbonate formation in different climatic conditions results in differing morphologies and mineralogies (Alsharhan and Kendall, 2003). Arid climate carbonates will have evaporite minerals such as gypsum, anhydrite, dolomite, and halite associated with them, or as layers stratigraphically adjacent to them (Butler, 1969; El-

Tabakh et al., 1997; El-Tabakh and Schreiber, 1998). Humid climate carbonates lack evaporite minerals and may exhibit epikarst (Klimchouk, 2004). Lacustrine carbonates can be found in most lakes in varying amounts today (Della Porta and Barilaro, 2011;

Harris et al., 2013), and in the geologic record (Gierlowski-Kordesch and Buchheim,

2003; Gierlowski-Kordesch and Park, 2004; Gierlowski-Kordesch, 2010). Lakes vary greatly in origin, depth, nature of and amount of sediment input, nature and amount of water input, organisms, salinity, and climate (Gierlowski-Kordesch and Park, 2004;

Gierlowski-Kordesch, 2010; Harris et al., 2013), and can form as the result of many different geologic processes including glaciations, mass wasting, fluvial meandering, tectonics, and volcanic activity (Gierlowski-Kordesch and Park, 2004). However, lakes formed as the result of tectonic forces (e.g. strike-slip, rift, foreland basins) are the most well-preserved in the geologic record (Gierlowski-Kordesch and Park, 2004).

Generally, lakes are classified into three categories: under-filled, balance-filled, and over-filled (Gierlowski-Kordesch, 1998; Gierlowski-Kordesch and Park, 2004;

Harris et al., 2013). Under-filled lakes are found in basins that have closed drainage

(endorheic), show a variety of contrasting lithologies, including siliciclastic, carbonate, and evaporite minerals, and tend to be chemically stratified (meromictic). Fluctuations in climate greatly affect these lakes (Gierlowski-Kordesch and Park, 2004). Balance-filled lakes alternate between closed and open hydrologies and tend to accumulate interbedded siliciclastic and carbonate sediments. Over-filled lakes (exorheric) have open hydrology, lower salinity, and stable shorelines (Harris et al., 2013). Climate fluctuations have little to no effect on these lakes (Gierlowski-Kordesch, 2010; Harris et al., 2013). Salinity will be higher in under-filled lakes and lowest in over-filled lakes because closed hydrology does not allow for dissolved salts to exit the basin, so they accumulate from crystallization due to evaporation (Gierlowski-Kordesch and Park, 2004). Lakes that formed in the Newark Basin varied among these three types throughout the basin’s history, starting over-filled and becoming increasingly under-filled as the basin evolved through the Late Triassic (Olsen et al., 1989; Schlische, 1992; Olsen, 1998).

While the sediments of the Newark Basin are very well studied, very little has been done with the paleosols that developed during periods of low sedimentation at the top of individual VHCs. Heffren (2008) studied facies changes in three separate VHCs, but made no mention of pedogenic features. Van Houten (1962), Olsen (1986a), and

Olsen and Kent (1996) noted the presence of root traces in mudstones, but did not expand on their observations. Schaller et al. (2011, 2012) analyzed pedogenic carbonate nodule

δ13 C data from the Central Atlantic Magmatic Province (CAMP) event in an attempt to correlate the splitting of Pangaea with the End-Triassic extinction. Smoot and Olsen

(1988) observed pedogenic features such as clay coatings, pedogenic slickensides, root structures, and carbonate nodules in the Newark Basin. However, the degree and nature

ssion, or wobble, of l with the Sun. inY-axis nts oval-shaped more orbit. ovitch over cycles 1 million (a) Axial years. prece e that axise Earth’s is tilted to relative orthogona orbit. represents Zero circular orbit, 8.0 represe – Cartoon representation basic the three of Milank 8

Figure the Earth. Unknownthe Earth. y-axis. Obliquity, (b) angl or degrees. Eccentricity,degrees. (c) roundness or Earth’s of Modified from Yu al. et (2008).

les found in the Newark Basin ight of each column.ight From each of Olsen al. et – Graphical representation the hierarchyof cyc of 9

with durations interpreted depth and to ranks the r (2010). Figure

18 of soil development was largely ignored in favor of a regional-scale, facies-oriented interpretation, and no detailed paleopedology was performed.

2.3.2 Paleosols

A paleosol is evidence of prolonged subaerial exposure that is preserved in the geologic record. Soils form as a result of biological, physical, and chemical modification of parent material over time. Soil formation requires an extended period (hundreds to tens of thousands of years) of landscape stability in order for these pedogenic processes to take place. Pedogenesis can create unconformities in the rock record from outcrop scale to regional scale (Kraus, 1999).

Paleosols occur in many depositional environments, including palustrine

(swamp), aeolian (wind-blown), and deltaic. However, the vast majority of paleosols have been described from paleo-alluvial environments (Pimental et al., 1996; Aslan and

Autin, 1998, 1999; Kraus, 1999; McCarthy and Plint, 2003; Terry, 2001; Atchley et al.,

2004, Hamer et al., 2007). These ancient soils record the paleoenvironmental conditions in which they were formed (Jenny, 1941; Retallack, 1994; Kraus, 1999; Terry, 2001).

The five main factors in soil formation include climate, organisms, relief, parent material, and time (CLORPT, Jenny, 1941). Some of these factors become more or less important as the soil develops. For instance, parent material is a greater contributing factor to soil characteristics in younger soils than older soils. Over time, leaching will remove the more mobile constituents (e.g. Ca, Mg, Na) and the soil will become relatively more enriched in silica and iron and aluminum oxides (Chesworth, 1973). The amount of relief present during pedogenesis greatly influences soil properties. High relief can cause severe erosion if the soil is on the shoulder of a slope while a soil at the base of the slope

k rs are Jurassic are rs . Figure 1 ject. ject. Green represents the Stockton Formation, dar c Formation,c represents red other and diabase, colo . From Olsen Kent (1996). and in as Key Figure 7 – Schematic drawing the Newarkof Basin Coring Pro 10

Figure blue the Lockatong Formation, light blue the Passai also See rocks.

20 would be thicker than normal due to the colluvial accumulation of sediment, giving the soil profile a pachic horizon (Birkeland, 1999).

Paleosols serve as a time-averaged record for these five factors in the form of soil chemistry, mineralogy, and morphology (Jenny, 1941; Kraus, 1999; Retallack, 2001).

However, these proxies can be altered by burial diagenesis (Retallack, 1991, 1994;

Wright, 1992; Pimentel et al., 1996; Kraus, 1999). Diagenesis can alter original oxidation state, color, mineralogy, and horizonation (Retallack, 1991). It is also possible for carbonate to accumulate in soils during diagenesis, making it difficult to distinguish from pedogenic carbonate (Pimentel et al., 1996). Pedogenic carbonate forms when the amount of rainfall that percolates through a soil is sufficient to leach calcium ions, but of insufficient amount to reach the water table. As the water is absorbed by plants or evaporates, the calcium carbonate is left behind. The depth to carbonate is a function of the average amount of rainfall. Jenny and Leonard (1935) found a positive relationship between mean annual precipitation (MAP) and carbonate depth in modern soils; the deeper the carbonate nodules, the higher the average rainfall. This method has been used with paleosols (Birkeland, 1999; Terry, 2001; Retallack, 2005), but reliability is lost once rainfall exceeds about 800 mm/yr (Retallack, 2005).

CHAPTER 3

METHODS

3.1 Field Work

3.1.1 Paleopedological Analysis

The exposure was carefully measured and units were delineated based on lithology and the nature of the contacts. Paleosol profiles were described, noting Munsell

(1975) color, reaction to HCl, grain size, soil structure, presence and size of root traces, and stratigraphic thickness. Measurements regarding soils are traditionally recorded as distance from the top of the profile. However, I measured strata in centimeters from the base of individual units and reference particular features as such. Approximately one hundred representative oriented and bulk samples were collected from various divisions of the three selected paleosols and their associated strata for further laboratory analysis.

3.1.2 Magnetic Susceptibility

Magnetic susceptibility (MS) was measured on the weathered surfaces of select

VHGs every 2 cm with a Bartington® MS2E in order to determine possible variation in sources of sediment or parent material (Blundell et al., 2009; Balsam et al., 2011). Rock units with elevated levels of magnetic minerals will react to a magnetic field more readily than rocks that are relatively less enriched (Singer et al., 1996). Magnetic susceptibility has been shown to serve as a proxy for plant roots and organic matter within paleosol profiles (Retallack et al., 2003).

3.2 Laboratory Analysis

3.2.1 Depth Ranks

Olsen (1986a) assigned depth ranks for the various facies within the Newark

Basin. However, I created my own system of site specific depth ranks in order to better reflect the facies changes observed at the Pottstown, PA site. My system is largely based on microscopic observations because features such as root traces, bioturbation, oncoliths, and relict bedding are more easily observed in thin section. Lithology contributes to the depth rank by separating largely subaerially exposed facies (mudstone) from subaqueous facies (carbonate-rich). Depth rank 0 represents rock units that are rarely or never subaqueous while depth rank 6 represents the deepest lake facies (Table 1).

Table 1 Description of Depth Ranks Depth Description Rank 0 Massive mudstone, root traces, bioturbation 1 Massive mudstone, bioturbation, algal mats, relict bedding 2 Massive to laminated mudstone, oncoliths possible, bioturbation 3 Laminated mudstone, various types of ripples common 4 Massive marlstone, calcic rip-up clasts common near top, rare oncoliths 5 Millimeter-scale laminations, carbonate interbedded with quartz-rich layers, brecciation 6 Millimeter-scale laminations, kerogen bearing carbonate, interbedded quartz-rich laminae

3.2.2 Soil Micromorphology

Oriented samples of each unit were cut and polished for micromorphological and mineralogical analysis. The samples were mounted to 5.08 cm x 7.62 cm glass slides and polished to a thickness of 30 µm (Brewer, 1964). Each sample was observed under a

Nikon E600 polarizing microscope to determine mineralogy, fabric, and the presence of

23 pedogenic features. Photomicrographs were taken using a Nikon DXM 1200F digital camera.

3.2.3 Clay Mineralogy

Clay minerals were identified using a Bruker D2 Phaser X-Ray Diffraction

(XRD) system at West Chester University. Analyses were done at 30 kV and 10 mA using CoKα radiation, and scanned from 4.451° to 34.996° 2 θ at a rate of 2.22° per minute.

Approximately 20 samples were prepared for analysis by powdering bulk samples using a mullite-chamber shatterbox. Each powder sample was then placed into plastic containers with deionized and distilled water and placed in a Hermle Labortechnik Z400 centrifuge for 12 minutes at 500 RPM to separate the clay fraction from the coarser sediment. The fluid from each container was decanted into a beaker and oriented using the Millipore® Filter Transfer Method prescribed by Moore and Reynolds (1997).

Samples estimated to have the highest chance of containing swelling clays (samples from paleosol profiles rather than lacustrine beds) were placed in a desiccator with ethylene glycol for at least 24 hours.

3.2.4 X-Ray Fluorescence

Bulk chemical composition was determined using X-Ray Fluorescence (XRF).

Ten bulk samples were powdered to ≤180 µm (80 mesh) using a mullite-chamber shatterbox. The powder was placed into vials, and sent to Franklin & Marshall College for analysis using a PANalytical 2404 X-ray fluorescence vacuum spectrometer equipped with a 4kW rhodium (Rh) X-ray tube (Franklin and Marshall, 2013). Major element samples were prepared by fusing a glass disk made of 0.4000 ± 0.0001 g whole rock

24 powder and 3.6000 ± 0.0002 g lithium tetraborate in a platinum crucible (Franklin and

Marshall, 2013). Trace element samples were pressed into a homogenized pellet of

7.0000 ± 0.0004 g whole rock powder and 1.4000 ± 0.0002 g copolywax powder

(Franklin and Marshall, 2013). Compositions in weight percent were converted into moles by dividing the data (ppm or percent oxide) by the molar mass of the element or oxide prior to calculating molecular weathering ratios (Sheldon and Tabor, 2009).

Molecular weathering ratios are used as proxies for pedogenic processes by comparing the relative abundances of elements (Sheldon and Tabor, 2009). Several molecular weathering ratios are used to infer relative intensity of weathering or associate

weathering with processes and products. Elevated ratios of have been used as a proxy for paleo-fertility of soil, though it has only been applied to paleosols from

weathered basaltic material (Sheldon and Tabor, 2009). The ratios and are used

to approximate the amount of soil leaching (Sheldon and Tabor, 2009), (hydrolysis) is a measure of base saturation and is useful for determining if soils are alkaline or acidic,

and (podzoliziation) is a proxy for the eluviation of organic matter and clay.

Trace elements such as copper (Cu) and nickel (Ni) can form complexes with organic matter, and their relative abundances can be used to determine zones of illuviation and eluviation (Terry, 2001; Kahnmann et al., 2008). Loss on ignition (LOI) has also been shown to serve as a useful proxy for organic matter (Salehi et al., 2011).

According to Sheldon and Tabor (2009), the ratio of can be used to detect shifts in the

provenance of the parent material. The ratios and are also used to determine changes in sediment source.

CHAPTER 4

RESULTS

A detailed stratigraphic section of the exposure was constructed using both field and microscopic observations (Fig. 11). Six VHCs were identified in this exposure. The uppermost three were selected for detailed analysis because they were the best developed, having sharp contacts between paleosol profiles and lake deepening events. A total of 6 paleosol profiles were also identified at this exposure, with the uppermost three selected for detailed analysis. The four paleosol profiles lower in the section are not associated with lacustrine units, which is necessary to test my hypothesis.

For the purposes of this study, VHCs will be grouped as the paleosol (division 3) of the underlying VHC, and the shallow lake (division 1), and the deep lake (division 2) of the next overlying VHC, rather than the traditional order (division 1, 2, 3), in order to relate the degree of paleosol development to subsequent lake development since establishment of the lacustrine environment ends pedogenesis. I refer to these as Van

Houten Groups (VHGs). The section was broken up into numbered units. A total of thirty-three units containing six VHGs were identified using lithologic contacts. Depth ranks were assigned using macroscopic and microscopic features (Fig. 12).

4.1 Lower Van Houten Group

The lower VHG (Fig. 12) contains only divisions 3 and 2, with pedogenic features present in Unit 16 (Van Houten division 3). Table 2 provides full unit descriptions.

Figure 11 – Measured section of the Pottstown exposure with individual unit numbers in italics.

Figure 12 – Van Houten Cycle-scale measured section showing depth rank and magnetic susceptibility to the right. Yellow, magenta, and blue columns to the left represent Van Houten Cycle divisions. Italicized numbers are individual rock units. Key as in Figure 11.

Description

Unit 16 is a weak red mudstone with relict bedding in the lower 30 cm (Table 2,

Figs. 4d and 12). The top third of the unit is more massive and contains sediment-filled root traces ranging in thickness from 0.1 to 0.5 mm. Many of these are clay-lined (Fig.

13b). Rare, irregularly shaped oncoliths are also present (Fig. 13c). Most clay in voids of this unit is unaligned except in the top 5 cm where insepic fabric is observed. A sharp, erosive contact is shared with overlying Unit 17.

Unit 17 (Van Houten division 2) is also a weak red mudstone. The bottom 85 cm and top 60 cm contain relict bedding, while the remaining 55 cm in the middle of this unit is more massive (Fig. 4e). Algal mats are present in somewhat regular intervals throughout the unit. Micromorphology of the lower section reveals unidirectional ripples, rip-up clasts and bioturbation (Fig. 14a - d; Table 2). However, anhydrite was not observed in thin section. The mineralogy of Unit 16 is mostly clay, quartz, and calcite with rare muscovite. The clay fraction is dominated by illite, hematite, quartz, and pyrolusite. Unit 17 is largely clay, quartz, and muscovite with some diagenetic sparry calcite.

Magnetic Susceptibility

No data were collected for this section due to MS unit failure to connect to the probe on multiple occasions.

Table 2 Unit Descriptions

Unit Macroscopic features Microscopic features VHC VHG Number Division 30 Bluish Gray (Gley 2 5/1). 84 Fining upward sequences range from 2 cm thick. Laminations 0.8 to 2 mm in thickness. Soft

approx. 5 mm thick. Some sediment deformation common. parts of weathered surface Quartz lenses ~2mm thick, some are yellow. with cross bedding. 29 Bluish Gray (Gley 2 5/1). 20 Mostly microspar carbonate with vfS 1 cm thick. Massive -sized, angular quartz grains marlstone, slight reaction peppered throughout. Distinct layer with HCl. of coarser material in middle and top of unit causes soft sediment deformation. 28 Dusky red (10R 4/2), 73 cm Sediment and diagenetically-filled 3 thick, carbonate nodules in root traces found throughout, largest top 10 cm. Massive ~1 mm dia. Upper VanUpper Houten Grouping mudstone. Root traces seen throughout. 21 Gley 2 2.5/5, 62 cm thick. Millimeter-scale fining upward 2 Laminations approx. 3 mm sequences range from 0.87 to 0.37 thick. Noticeably coarsens mm thick. Coarse material mostly upward toward top. vfS quartz. Liesegang rings, soft sediment deformation, and quartz lenses observed. Dolomite rhombs in top portion. 20 Bluish gray (Gley 2 5/5pb), Mostly microspar carbonate with vfS 1 25 cm thick. Massive. -sized, angular quartz grains Weak reaction with HCl. peppered throughout. Distinct layer Marlstone. of coarser material in middle and top of unit topped by fine siliciclastic material and cross bedding. 19 Dusky red (10R 4/2), 104 Distinct layer at 10 cm rich in larger 3 cm thick, massive grains of metamorphic origin with mudstone, carbonate oncoliths. Rhizobrecciation is seen at nodules in top 16 cm. the top of the unit, along with Middle Houten GroupingVan Lower 60 cm possibly after diagenetically-filled root traces. relict bedding. Root traces seen at top. 17 Dusky red (10R 4/2), 200 Relict bedding common. 2 cm thick, top 60 cm Crossbedding and rip up clasts are resembles relict bedding. seen at 20 cm. Trough cross 55 cm thick massive section bedding, planar beds, bioturbation, in the middle with algal and climbing ripples are observed laminations. Bottom 85 cm 185 cm up. also resembles relict bedding. 16 Dusky red (10R 4/2), 51 cm Soft sediment deformation, relict 3 Grouping thick, bottom 30 cm relict bedding, and algal mats are observed bedding, fractured. Clayey in lower portion of unit. Upper VanLower Houten silt. Sediment-filled root portion contains many sediment- traces seen at top. filled root traces ~0.1 mm diameter.

4.2 Middle Van Houten Group

The Middle VHG (Fig. 12) contains all three divisions of the VHC model (Fig. 3).

This is the most pronounced (well-developed) VHG in my section. Units 19, 20, and 21 represent divisions 3, 1, and 2 respectively.

Description

Unit 19 is a dusky red massive mudstone (Table 2) with calcium carbonate nodules in the top 10 cm (Fig. 15a). A layer of coarser materials is present 10 cm from the bottom of the unit consisting of mostly clay with large (500 – 800 µm) polycrystalline clasts of quartz, fine sand-sized (~100 µm) sub-angular quartz, microcline, muscovite, orthoclase, and plagioclase. Some grains are covered with oriented clay (skelsepic fabric,

Fig. 15b). Root traces are very rare, about 250 µm in diameter, and filled with calcite or chalcedony at the bottom of the unit (Fig. 16a). The top of the unit contains clay-lined root traces of similar size preserved with calcite and chalcedony (Fig. 17b). Spherical algal accumulations (oncoliths) are locally present in great numbers in this unit and range from 0.1 to 0.25 mm in diameter. Most are smaller than 0.2 mm. The sub-concentric rings of the oncoliths are recrystallized with iron oxide (likely hematite, Fig. 16c). This unit shares a sharp, erosive contact with Unit 20.

Division 1 of this VHG is a massive marl layer with a weak reaction to HCl

(Table 2). Angular to subangular quartz grains are distributed diffusely throughout most of this unit with occasional fine sand-sized quartz grains and rare zircons. Rounded micritic carbonate clasts (~1-4 mm) are found at the top of this unit, while smaller clasts

(<1 mm) are found in the middle (Fig. 17a, b). Just above the carbonate clasts is a layer of finely laminated, clay-sized siliciclastic material followed by coarser material

). ). ) several) B ed as algal mats as ed (m). ( zed lightzed (XPL) except polarized plane for ) Oncoid ) fragment from Unit 16. Red scale C ) Lower) 8 cm of Unit 16 showing bedding relict (r A A. A. – Photomicrographs Unit of 16. ( -filled root traces theat top Unit of 16. ( -parallel lines theat top bottom and interpret are 13

Figure sub The sediment isbar 100 µm. All in photomicrographs polari cross light (PPL) in

Figure 14 – Photomicrographs of Unit 17. (A) Relict bedding, unidirectional cross bedding, and rip up clasts at 20 cm (XPL). ( B) Photomicrographs of a burrow from Unit 17 at 185 cm (green arrow, XPL). (C and D) Photomicrographs of burrows (green arrows) at 185 cm (PPL).

33 that records unidirectional cross bedding (Fig. 17c and d). There is a sharp, erosive contact with Unit 21.

Division 2 of this VHG is markedly darker and more laminated than the surrounding units (Fig. 18a). Laminations range from 1 to 3 mm in thickness (Fig. 18b) consisting of interbedded fine sand-sized quartz and microspar calcite with rare muscovite. A fuel oil-like smell was noticed upon cutting, suggesting that kerogen is present within the rock. Microscopic analysis revealed that millimeter-scale fining upward sequences dominate the lower portion of this unit (Fig. 18c).

Magnetic Susceptibility

This section showed the highest correlation between facies change and magnetic susceptibility. Readings stay relatively low throughout Units 19 and 20 with a marked increase in Unit 21 as lithology changes from marl to shale (Fig.12, Appendix C).

4.3 Upper Van Houten Group

This VHG is moderately-well expressed with all divisions present (Fig. 12).

Units 28, 29, and 30 represent VHC divisions 3, 1, and 2 respectively.

Description

Unit 28 is a dusky red mudstone and has macroscopic hair-line root traces throughout (Fig. 19a, b). Carbonate nodules approximately 2 mm in diameter are preserved near the top of this unit (Fig. 19c). Both diagenetically filled (calcite and chalcedony) and sediment filled roots are present in thin section. Diagenetically-filled roots are found closer to the bottom of the unit while the sediment-filled roots are found near the top of the unit (Fig. 19d, e, f, g). Division 1 in this VHG is not as thick as the

34 middle VHG. It is bluish gray, massive, and reacts weakly with HCl. Carbonate accumulation is seen near its top (Fig. 17e). The lower two-thirds of division 1 consist of fine carbonate with occasional quartz grains. The top third contains coarser sediment which induced soft sediment deformation. Some of these larger grains are rounded carbonate clasts with fine sand-sized angular quartz. A sharp, erosive contact separates this Unit from Unit 30.

Unit 30 is also bluish gray (Fig. 18d). Laminations range from 2 to 5 mm in thickness in hand sample (Fig. 17f). Thin section analysis reveals fining upward sequences measuring 0.2 to 1 mm in thickness (Fig. 20a, b). Other features present in thin section include soft sediment deformation, cross lamination, and sand lenses.

Magnetic Susceptibility

Magnetic susceptibility readings were relatively low for units 28 and 29. MS readings markedly increased in the middle of Unit 30 and stayed relatively high throughout Unit 30 (Fig. 11, Appendix C).

4.4 Clay Mineralogy

X-ray diffraction analysis of all of the soil samples yielded the same peaks (Fig.

21), indicating the presence of illite, kaolinite, quartz, hematite, chlorite, and pyrolusite in the clay-sized fraction.

Figure 15 – Photograph of Unit 19 in outcrop and photomicrographs showing clay fabric (A) Calcium carbonate nodules (arrows) at the top of Unit 19. (B) Photomicrograph showing skelsepic clay fabric (arrow) in Unit 19 (XPL). Large grains are quartz. (C) Photomicrograph showing skelsepic clay fabric (arrow) coating quartz grains in Unit 19 (XPL).

Figure 16 – Photomicrographs of features within Unit 19. ( A) Root trace filled with calcite and chalcedony surrounding a quartz grain at 10 cm (XPL). ( B) Root trace filled with calcite and chalcedony with clay lining at 100 cm (XPL). ( C-E) Oncoliths with hematite coatings at 10 cm. Note variable morphology (PPL). Cyan cross indicates horizontal orientation.

4.5 Molecular Weathering Ratios

Fig. 22 graphically represents results in regards to , , , , , Loss

on Ignition (LOI), copper (Cu), nickel (Ni), , , and for the three paleosol units

(Table 3, Units 16, 19, and 28). See appendix B for full data set. , , , and remain relatively low throughout the three paleosol profiles with only minor fluctuations.

LOI tends to be higher at the tops of Units 19 and 28, but remains approximately the

same throughout Unit 16. remains approximately the same throughout the profiles except in Unit 28 where there is a spike at 45 cm.

Figure 17 – Photomicrographs of Unit 20 and polished slabs from Units 29 and 30. ( A) Picture of thin section at the top of Unit 20. Note the rounded carbonate clasts (y) and the finely laminated, fine-grained siliciclastic layer at the top (s). Scale bar is approximately 1 cm. ( B) The same thin section as seen under a polarizing microscope. Image compiled using over 60 different photomicrographs. Note the grain size increase in the middle compared to the surrounding rock (XPL). Red bar is approximately 4 mm. (C) Polished slab of Unit 20. Each square is one inch. ( D) Photomicrograph of boxed area from (C) showing cross bedding with blue arrow indicating flow direction (XPL). (E) Polished slab of Unit 29. Undulatory line is coarser sediment (s) overlying and deforming the finer sediment below. Brightly colored irregular ‘blobs’ at the top (c) are calcium carbonate-rich zones. ( F) Polished slab of Unit 30. Darker bands (b) represent coarser sediment. Dark bands (d) that trend downward are likely composed of hematite.

Figure 18 – Photographs of various units within the middle Van Houten Group with a photograph of Unit 30 for comparison. (A) Units 20 and 21delineated by yellow line. Note that Unit 21 is darker than the surrounding rocks. Marker for scale. ( B) Close-up view of laminations in Unit 21. Arrow indicates up direction. ( C) Photomicrograph of fining upward sequences from Unit 21 (rhythmites, XPL). (D) Photograph of Units 29- 31. Yellow lines delineate unit contacts. Note the lighter weathered surface compared to Unit 21. Scale bar is approximately 20 cm.

Figure 19 – Photographs and photomicrographs of Unit 28. ( A) Hair-line root traces can be seen throughout the unit at outcrop scale. Scale bar is approximately 2 cm. ( B) Close- up of a root trace in outcrop. Scale bar is approximately 4 cm. ( C) Calcium carbonate nodules (n) found at the top of Unit 28. Scale bar is approximately 2 cm. ( D) Diagenetically-filled root trace at 5 cm containing carbonate and chalcedony. ( E) Sediment-filled root trace at 35 cm. ( F) Diagenetically-filled root trace at 35 cm containing carbonate and chalcedony. ( G) Diagenetically-filled root trace at 35 cm containing carbonate and chalcedony. All photomicrographs in XPL.

Figure 20 – Photomicrographs from Unit 30 (XPL). ( A) Interlayering at 5 cm of quartz and calcium carbonate with clay-rich clasts. Red bar is approximately 2 mm. ( B) Fining upward sequences (rhythmites) at 10 cm. ( C) Coarser layers with increased quartz content become spaced farther apart higher in the unit (65 cm up). Note pyrolusite dendrites (d).

), hematite), and (H), cobalt (Co) radiation. Peaks illite kaolinite (I), (K), chlorite (C), quartz (Q – X-ray diffractogram paleosols of and using lakes (P). 21

Figure indicate of the presence pyrolusite

. ted paleosols with profiles generalized to the left – Molecular weathering– Molecular ratios each of of the selec 22

Figure

Table 3 Calculated Molecular Weathering Ratios

Ba/Sr Bases/Ti Bases/Al 2O3 Sample Number Value Error ± Value Error ± Value Error ±

Unit 28, 70 cm 1.28 0.02 33.52 18.74 2.21 0.31 Unit 28, 45 cm 0.83 0.02 25.22 12.76 1.66 0.22 Unit 28, 5 cm 1.78 0.04 17.65 8.18 1.13 0.14 Unit 21, 20 cm 0.61 0.01 41.38 25.92 2.00 0.23 Unit 19, 102 cm 0.59 0.01 41.12 22.66 2.61 0.35 Unit 19, 10 cm 1.63 0.04 19.16 9.72 1.15 0.15 Unit 17, 95 cm 2.20 0.07 11.19 5.20 0.93 0.16 Unit 16, 52 cm 1.56 0.04 19.52 9.13 1.32 0.17 Unit 16, 42 cm 1.39 0.03 19.12 8.94 1.29 0.17 Unit 16, 10 cm 1.55 0.04 23.51 10.96 1.55 0.19

Table 3 Calculated Molecular Weathering Ratios (continued) SiO /Al O P O /TiO LOI (%) Sample Number 2 2 3 2 5 2 Value Error ± Value Error ± Value Error ± Unit 28, 70 cm 4.32 0.62 0.08 0.11 8.80 0.43 Unit 28, 45 cm 3.88 0.51 0.07 0.10 6.03 0.35 Unit 28, 5 cm 3.42 0.41 0.07 0.09 3.89 0.31 Unit 21, 20 cm 3.12 0.39 0.21 0.18 7.90 0.26 Unit 19, 102 cm 3.74 0.52 0.11 0.12 10.67 0.37 Unit 19, 10 cm 3.57 0.43 0.07 0.10 4.63 0.31 Unit 17, 95 cm 5.22 0.76 0.06 0.09 1.67 0.44 Unit 16, 52 cm 3.79 0.47 0.08 0.09 4.88 0.38 Unit 16, 42 cm 3.75 0.47 0.08 0.09 4.35 0.33 Unit 16, 10 cm 3.41 0.42 0.08 0.09 6.57 0.30

Table 3 Calculated Molecular Weathering Ratios (continued) Ti/Al U/Th La/Ce Sample Number Value Error ± Value Error ± Value Error ± Unit 28, 70 cm 0.07 0.04 0.33 0.05 0.46 0.02 Unit 28, 45 cm 0.07 0.03 0.30 0.07 0.44 0.02 Unit 28, 5 cm 0.06 0.03 0.18 0.03 0.46 0.02 Unit 21, 20 cm 0.05 0.03 0.25 0.11 0.45 0.02 Unit 19, 102 cm 0.06 0.04 0.61 0.09 0.38 0.02 Unit 19, 10 cm 0.06 0.03 0.09 0.03 0.40 0.01 Unit 17, 95 cm 0.08 0.04 0.25 0.03 0.52 0.02 Unit 16, 52 cm 0.07 0.03 0.19 0.04 0.45 0.02 Unit 16, 42 cm 0.07 0.03 0.15 0.03 0.40 0.02 Unit 16, 10 cm 0.07 0.03 0.09 0.04 0.43 0.02

CHAPTER 5

DISCUSSION

The CLORPT conditions under which these paleosols formed did not affect pedogenesis equally. Differences in soils are seen as the result of time and proximity to lake shore or channel. All soils in this section resemble Entisols according to the Soil

Survey Staff (2010), or Protosols according to Mack et al. (1993). Climate, time, and relief due to subsidence also affected the development of lakes, resulting in deposition of differing depth-controlled facies.

5.1 Agents of Soil Formation

5.1.1 Climate

Climate is a time-averaged measure of weather, specifically, of temperature and the amount of precipitation. According to Olsen (1986b) and Kent et al. (1995), the

Newark Basin was located at approximately 8°N paleo-latitude at the time of deposition.

This is the approximate location of modern-day Honduras, Venezuela, or the Philippines.

This depositional system is more prone to basin-wide climate changes due to its landlocked nature and potential to vary between hydrologically open and closed. The paleosols found at this site are poorly developed and probably formed over a few hundred to possibly 1,000 years, which is insufficient time for climate to significantly affect these soils. The paleosol associated with the middle VHG (deepest lake, Units 19 - 21) is the least developed paleosol in this section as evidenced by the small diameter (<0.25 mm) and rarely occurring root traces voids. Greater precipitation likely caused the sedimentation rate or the water table to be too high, thus quickly covering the paleosurface and ending pedogenesis. The paleosol associated with the lower VHG is the most

47 developed (relatively) of the three as evidenced by numerous clay-lined, thicker (>0.25 mm) root traces. This suggests that there was sufficient time for clay to translocate and cover the outside wall of the root. There was also sufficient time for the root to decay and for sediment to fill in the void. While each paleosol profile may have formed under different climate conditions, they are not sufficiently developed to determine this.

Therefore, the differences in development observed between these three profiles are more likely due to other CLORPT factors.

5.1.2 Organisms

Root traces, burrows, and algal mats are seen throughout this section. Burrows range from meniscate (Fig. 22a) to sediment-filled (Fig. 22b, c). Roots are relatively thin

(<1 mm) in these paleosols with the thickest roots in Unit 28 (Fig. 19e, Upper VHC,

Division 3). All root traces in the section are vertically oriented. Some root traces are filled with sediment and lined with clay. This suggests that the water table was rarely at the surface and that the soils were at least moderately drained. Root traces filled with calcite and chalcedony are likely roots that were buried and decayed, creating a void that was later filled by diagenetic mineralization. Roots provided pathways for water to move dissolved ions through the soil and to translocate clay.

Oncoliths are concentrated in the bottom 10 cm of Unit 19 and are accompanied by much larger grains (up to 1 mm) than are seen in the rest of the section. The oncoliths had no effect on soil formation by themselves, but the process that transported them to this location (e.g. flood event and associated parent materials) likely did. Organisms had little effect on the substrate in this section apart from providing preferential pathways for clay to be translocated and disrupting relict bedding.

Figure 23 – Photographs of bioturbation features within the study area and a photomicrograph from Unit 17. ( A) Green arrow point to meniscate burrow from Unit 17. Blue arrow points in up direction. Scale bar is approximately 1 cm. ( B) Sediment- filled burrow in unoriented rock found as float. Scale bar is approximately 1 cm. ( C) Sediment-filled burrow protruding from unoriented rock from float. Scale bar is approximately 1 cm. (D) Photomicrograph mosaic of Unit 17 at 185 cm. Crossbedding (t), planar bedding (p), and burrow (b). Scale bar is 4 mm.

5.1.3 Parent Material

This location in particular was relatively far from the sediment source as evidenced by the dominance of silt and clay. It is important to note that there are pulses of sediment that are distinctly different from the majority of the exposure. For example, lower in the section massive units of a markedly larger grain size are interbedded with mudstones (Fig. 11, Units 6, 9, and 13). These units are the VHC (Division 1) analogue to the marl units found in the middle and upper VHG. The largest grain size ranges from fine sand to very fine sand, and are very well sorted, rounded, and lack sedimentary structures. It is possible that these represent fluvial deposits resulting from an increase of precipitation due to orbital forcing. However interpretations are limited due to the lack of sedimentary structures such as cross bedding. The marl layers (Fig. 12, Units 20 and 29) record periods of low lake level and chemical precipitation of carbonate. Unit 20 displays evidence of fluctuations in energy (Fig. 18a, b), while Unit 29 records steady conditions (Fig. 18e). Both units show an increase in grain size toward the top that include rounded carbonate clasts. In Unit 20 this is followed by an influx of fine cross bedded siliciclastic sediments with mixed siliciclastic and carbonate deposited on top.

Unit 29 lacks sedimentary structures and clay-sized siliciclastics. It is unclear whether the rounded carbonate clasts found in Units 20 and 29 were sourced from within the basin, formed by organisms, or sourced from Paleozoic carbonates. Oncoliths are very rare in

Unit 20 and have not been observed in Unit 29.

The bottom 10 cm of Unit 19 has a unique mineralogy compared to the rest of the section. Here, grains of highly fractured quartz as large as 375 µm in diameter (average

125 µm) exhibit undulatory extinction and sutured grains (Fig. 15b, c), indicating a

50 gneissic parent rock. Oncoliths are found in great abundance among these grains. Other grains are as large as 1 mm in diameter, rounded to sub-rounded, matrix to grain- supported, and include polycrystalline quartz, microcline, orthoclase, and plagioclase.

This suggests that these grains and oncoliths were deposited relatively quickly by a stronger flow of water, perhaps in a flooding event. The inclusion of relatively coarse minerals, which are expected to be found proximal to the sediment source, suggests that an increase precipitation caused the energy of local streams to increase, allowing rapid down-gradient transport from the nearby metamorphic terrane. The presence of chlorite, as indicated by XRD results (Fig. 21), provides corroborating evidence for metamorphic parent rock.

With the exception of the bottom 10 cm of Unit 19, parent material was relatively consistent throughout the paleosol profiles in regards to grain size and composition.

While parent material has the greatest influence on a soil’s chemistry and fabric early in development, other CLORPT factors were more dominant in controlling pedogenesis.

5.1.4 Relief

The asymmetric shape (half-graben) of the Triassic Basins caused sediment emptying into them to partition, with the coarser-grained material on the steeper side, proximal to the bounding fault (Ramapo, Fig. 1), and the finer material distal to the fault, resulting in a gentle gradient (Olsen, 1990; Smoot and Olsen, 1994; Harris et al., 2013,

Fig. 24). The paleotopography of this ancient landscape was likely nearly flat, sloping perhaps 1 to 5 degrees to the northwest due to the constant infilling of the asymmetrical half graben. The high relief of the provinces surrounding the Newark Basin, Paleozoic sedimentary rocks to the northwest with Late Precambrian to Paleozoic metamorphic

Figure 24 – Schematic drawings comparing the facies distribution of southern (Richmond-type), middle (Newark-type), and northern (Fundy-type) rift basins. From Olsen et al. (2010).

52 rocks to the southeast, served as a steady source of sediment. Local elevation differences likely played a larger factor in soil formation than regional relief (i.e. half-graben architecture). Proximity to channels can inhibit soil formation as flooding events cause high sedimentation or even soil erosion. Soils that are too close to the lake shore would be prone to inundation with water for extended periods of time due to lake level rise.

These conditions are a function of the location in the basin relative to the bounding fault since the lake would be the deepest at the basin center. Soil formation is also inhibited when the water table stays near the surface. Some root traces, such as those in Unit 19 and the bottom on Unit 28, are diagenetically filled (with calcite and chalcedony) and lack clay linings. This suggests rapid burial or a high water table that prevented the translocation of clay. Although, evidence of hydromorphic conditions, such as mottles or gleyed soils, is absent.

5.1.5 Time

The duration of pedogenesis is difficult to quantify, even in modern soils

(Birkeland, 1999). The weakly developed nature of these paleosols suggests that pedogenesis did not have enough time to generate horizons. According to Birkeland

(1999), Bt horizons, sections of the soil profile enriched in translocated clay, take between 10,000 and 100,000 years to form, while Bw horizons, sections of the soil profile that have differing color and structure from the A and C horizons, take between

1,000 and 10,000 years to form.

Based on the lack of higher order horizons, it is apparent that paleosols in my section probably did not develop for more than a few thousand years at most, or other factors could have hindered the pedogenic process (e.g. high sedimentation rates,

53 saturated soils). It is for this reason that I consider time to be the dominant CLORPT factor in paleosol development in this section.

5.2 Molecular Weathering Ratios

The ratio of indicates that the paleosols are poorly leached ( ≤2) throughout the

respective profiles. The ratio of (hydrolysis) ranges between 1 and 3, suggesting that all paleosols are alkaline or poorly developed (Birkeland, 1999). Copper (Cu) and nickel (Ni) concentrations are lower than average Earth crust throughout the section, and

suggest a felsic parent rock. The ratio also supports a felsic parent rock (Yaroshevsky,

2006). These data are consistent with petrographic observations. However, depth of burial (Schlische, 1992) indicates that diagenetic fluids likely changed the chemistry of the strata by adding or subtracting mobile elements such as Sr, Ca, K, Na, and Mg. Thus, it is very unlikely that these data reflect the original chemistry of the paleosols/sediment

(Fowler and Yang, 2003).

5.3 Magnetic Susceptibility

The goal of using this method was to test the idea that magnetic susceptibility could be used to quickly identify Van Houten Cycles in the rock record, even if the division boundaries were not apparent in outcrop. Facies changes were best detected using magnetic susceptibility in the middle VHG, which is also the best expressed.

However, the signal of the MS meter attenuates within a very short distance from the tip of the probe. Therefore a solid contact, one without air space, is necessary for an accurate measurement. This outcrop varies from massive to heavily fractured (pencil fracture), causing readings from fractured portions of rock to be inaccurate or

54 inconsistent. It is for this reason that that magnetic susceptibility would be more useful on drill cores, such as those from the Newark Basin Coring Project (Olsen et al., 1996).

Pierson et al. (2013) used MS to test correlations between MS readings and changes in facies in cores from the Newark Basin Coring Project (Olsen et al., 1996). However, they expressed dissatisfaction with the method (Pierson, J., 2013; pers. comm.) citing unreliable and inconsistent readings that did not match up with observable features in the core (e.g. color changes). Additionally, MS readings from lower in the section proved to be less useful for finding contacts. The lower VHG has no MS data because the instrument could not recognize the probe. Readings were taken on weathered surfaces because exposing a fresh surface would be labor intensive (thereby negating the utility of

MS). Since magnetic susceptibility only seems to show promise for sections where facies changes are obvious, it is my conclusion that is not useful for the purpose of locating weak facies changes.

5.4 Diagenesis

Burial diagenesis is defined as the physical and chemical processes that sediments experience upon burial (Fowler and Yang, 2003; Blatt et al., 2006). Unfortunately, this can alter the original chemistry, structure, mineralogy, organic matter content, porosity, thickness, and color of paleosols (Retallack, 1991). It is estimated that 2 km of sediment has been removed by erosion since deposition (Schlische, 1992). This depth provides sufficient temperature for illitization of smectite to occur, causing addition of K and loss of Ca, Mg, and Na (Fowler and Yang, 2003). Rocks in my study section are mostly brick red, but approximately 35 m further up section there is a gradation from brick red to dark blue caused by gleization (reduction of iron oxides and hydroxides by anaerobic bacteria)

55 of organic matter within deep lacustrine deposits (Olsen, 1986a; Olsen et al., 1996;

Gierlowski-Kordesch, 1998).

Carbonate nodules are found at certain stratigraphic levels in my section (Fig. 15a and Fig. 19c). It was first thought that these were pedogenic in origin. However, the morphologies and distribution of these nodules, coupled with the fact that carbonate nodules require extended time to form, suggests that the nodules were not pedogenic.

Paleosols in this section likely had insufficient time to develop carbonate nodules of this size. The nodules are likely a result of groundwater rise and subsequent precipitation , eventually forming the lake.

While I observed pedoturbation in Triassic paleosols in nearby Phoenixville, PA, there is no evidence for the presence of expanding clays in outcrop scale or in X-ray diffraction analysis (Fig. 21) for the Pottstown site. Expanding clays that were present would have been illitized during diagenesis (Retallack, 1991; Fowler and Yang, 2003).

Void fills tend to have chalcedony along the outside wall of the void and carbonate on the inside (Fig. 19f). This suggests that the fluid present during diagenesis experienced a change in pH from acidic to basic. Chalcedony was originally deposited on the inside wall of the voids, followed by an increase in pH and precipitation of carbonate in the remaining void space, possibly dissolving some of the SiO 2 in the process. These changes are consistent with groundwater rise and subsequent formation of an alkaline lake (Gierlowski-Kordesch, 2010).

5.5 Lake Facies and Marl Units

Lower Van Houten Group

Divisions 1 and 2 of the VHGs in this section exhibit a variety of characteristics.

It is worth noting that the lower VHG lacks Division 1. It is possible that it was eroded as Unit 17 (Division 2) shares an erosive contact with Unit 16 (Fig. 4e). Unit 17 has rip- up clasts (Fig. 14a) and cross and planar bedding (Fig. 23d). Asymmetrical ripples suggest that this unit was experiencing unidirectional flow of water toward a deeper part of the basin, forming a lake. However, there is no evidence that this lake inundated this part of the basin for a significant amount of time. Unit 17 changes from fractured to massive about 80 cm from the contact, above which algal laminations can be found.

Middle Van Houten Group

The marl layer in the middle VHG (Unit 20) is massive with a distinct grain size increase at the top. Grain size fluctuations are seen throughout the unit as well.

Increased grain size indicates that the system’s energy also increased. This could be due to two different factors: (a) lake level fluctuation or (b) pulses of increased sediment input. Lake level fall could have caused progradation of coarser material into the basin, while lake level rise could have left a transgressive lag. This is not specifically observed in this unit. Coarsening upward sequences are not present and smaller grains are not removed; only the addition of larger ones is seen. Packages of larger gains fine upward and are matrix supported, which is expected in a high energy flow regime. Therefore, increased sediment input due to increased system energy (flood event) is the more probable cause. The transition from fine grained carbonate to siliciclastic sediment at the

57 top of Unit 20 is punctuated by relatively large (1-3.5 mm) rounded micritic carbonate clasts, oncoliths, and zircons. An increase in energy, such as a flooding event, is the likely cause. Whether the carbonate clasts are intra-basinal or extra-basinal is not clear based on the evidence gathered in this study. Just above the clasts, a layer of fine grained siliciclastics is preserved, indicating the shutdown of carbonate production that formed the marl layer and a transition to low energy siliciclastic-dominated sedimentation. This transition could have resulted from increased turbidity from an influx of siliciclastic input or dilution of the lake water from an outside source (Harris et al., 2013). The coarser grained microspar calcite and siliciclastic sediment on top of the siliciclastic layer marks a recovery of carbonate production and a decrease in turbidity (Fig. 17a, b, c, d).

The deepest lake facies is found in this VHG. Millimeter-scale fining upward sequences are found throughout Unit 21 (Division 2). Olsen (pers. comm., 2012) called these lake turbidites, however this term denotes specific processes. These could also be varves, but this term suffers from the same problem. I therefore find it most reasonable to refer to these as rhythmites (Gierlowski-Kordesch, 2010), or simply fining upward sequences (Fig. 18b, c), because they are non-genetic terms. The coarse grains in these sequences are largely composed of quartz. These rhythmites formed as a result of increased energy and were likely deposited over a relatively short time. Some rhythmites have sharp bottom and top contacts, which could indicate rapid deposition of coarse material followed by subsequent slow carbonate deposition on top of them, while others are true fining upward sequences. This interlayering of carbonate and siliciclastic material may reflect seasonality in precipitation. The presence of kerogen in this unit suggests that it was a deep, chemically stratified lake (Smoot and Olsen, 1994).

Dark lines often accompany the soft sediment deformation and cross cut the rhythmites in Unit 21. They resemble mud cracks in hand sample, but do not have the characteristic wedge shape when observed in thin section. Liesegang rings radiate out from these dark lines. These dark cracks are composed of iron oxide-enriched sediments which cut through the layers and are of an undetermined origin (Fig. 24a and b).

Distinct dolomite rhombohedra can be seen toward the top of this unit (Fig. 24c).

According to El-Tabakh et al. (1997), evaporite pseudomorphs should be found near the top of each lake section. The localized distribution and displacive growth of the dolomite rhombohedra suggest that they were likely deposited as original evaporite minerals (El-

Tabakh, 1994; El-Tabakh and Schreiber, 1998).

Upper Van Houten Group

This marl layer (Unit 29) is thinner than the one in the middle VHG (Table 2) and exhibits a very similar morphology. However, the grain size is consistent throughout the unit until the upper third where coarser sediment starts to dominate and induce soft sediment deformation. Unlike the marl unit in Unit 20, there is no fine grained siliciclastic portion to this marl, and thus the carbonate production factory was likely never interrupted. The origin of the large carbonate clasts in this unit is likely the same for the underlying marl layer. Secondary carbonate can be seen as bright, irregularly shaped accumulations near the contact of this unit with the overlying lake facies deposits

(17e). This accumulation was likely an artifact of groundwater rise and subsequent lake formation.

) ) B cutting m the thinof section. ( ) rings Liesegang radiate from outward cross- -cutting that they bands reveal are composed of A ) Dolomite) 50at rhombohedra cm (XPL). C Note soft sediment deformation the bottotoward (s) – Photomicrographs from Unit 21. ( with some sediment gains ( (h). 25

Figure bands (XPL).opaque lightReflected Photomicrograph dark, of cross hematite

Division 2 (Unit 30) has sub-millimeter to millimeter-scale laminations

(rhythmites) similar to the underlying lake, except they are generally farther apart and resemble lenses more so than fining upward sequences, especially toward the top of the unit. The distance between, and lateral continuity of, each lens becomes greater higher in the unit (Fig. 25). Soft sediment deformation and pyrolusite dendrites are common (Fig.

25b, c). Pyrolusite indicates highly oxic and high pH conditions during diagenesis

(MinDat.org, 2013). One lens preserved cross bedding, indicating a relatively higher flow regime (Fig. 25d). Coarse layers are comprised of very fine quartz sand, similar to the underlying lake. However, there is noticeably more siliciclastic influence and no hint of kerogen in this lake, suggesting that it was shallower than the lake in the stratigraphically lower VHG or not chemically stratified (Unit 21). Pulses of coarse siliciclastic material introduced during times of high energy (i.e. flood events) are more likely to be deposited closer to the source due to differential settling velocities, thus the shoreline for this particular lake would have been closer at this time compared to the stratigraphically lower deep lake. Thus, the presence of coarser sediment in Unit 30 when compared to Unit 21 indicates that the lake of the upper VHG was shallower than the lake in the middle VHG.

5.6 Orbital Forcing

Milankovitch cycles have been identified as a cause of periodic climate change

(Hayes et al., 1976; Yu et al., 2008). It is well-established that the stratigraphic cyclicity in this basin was caused by perturbations in Earth’s orbit (Van Houten, 1962, 1964;

Olsen, 1986a, 1986b; Olsen and Kent, 1996; Olsen et al., 1996; Kent and Olsen, 1999).

While the main control on climate in this strata is the precession of the equinoxes (~21

Figure 26 – Photomicrographs from Unit 30 (XPL). ( A) Quartz-rich clast with sediment compacting around it. ( B) Coarse material deposited on top of finer material induced soft sediment deformation. ( C) Pyrolusite dendrites radiating from cracks. ( D) Unidirectional crossbeds in a sand lens at 68 cm. Dark blue arrow indicates flow direction.

62 kyr), it is greatly affected by the peaks and troughs of the cycles of obliquity (~41 kyr)and eccentricity (~100 kyr). That is, the higher-order cycles can cancel out or enhance the lower order cycles depending on when and how they align. This ultimately affects the amount of insolation received by the Earth (Fig. 8).

Greater variation in insolation would lead to more distinct lithologic changes throughout the rock record, such as lacustrine verses alluvial, as the varied solar input would create times of increased and decreased precipitation. However, P. Olsen (pers. comm., 2012) said that it is actually during the times of relative steady insolation (low variability) that deep lakes are formed and preserved, and that a large variability in precipitation would not readily be preserved in the rock record due to competing weather patterns and erosion. In order to form deep lakes, there must be a steady flow of precipitation to fill them. To test this hypothesis, my section must be correlated with

Olsen and Kent’s (1996) drill core in order to determine the amplitude of the

Milankovitch cycles seen in my section. Their data can be used to determine the relative amplitudes (i.e. are the cycles canceling out or enhancing each other) of each cycle.

Increased lake depth could also be explained by an increase in accommodation space due to subsidence, providing an opportunity for water and sediment to fill the basin.

Lower in the section, three VHGs are identified based on root traces and massive sandstone layers since there are no lake beds. Based on my communication with P. Olsen

(2012), I attribute the lack of lake beds in the 3 VHCs lower in the section (associated with Units 6, 9, and 13) to greater variation in insolation over approximately 60,000 years

(~21 kyr each cycle). Conditions promoting high variability in insolation would be a more elliptical orbit coupled with a high angle of obliquity (tilt of Earth’s axis, Yu et al.,

2008). The precessional effect would be enhanced by a relatively elliptical orbit as well.

This is because precession affects whether the Northern Hemisphere of Earth is tilting toward the Sun when it is closest in its orbit or when it is farthest. For instance, today the

Northern Hemisphere is pointed toward the Sun when we are farthest from the Sun in our orbit, which will not be the case 10,000 years from now.

The lower VHG (Units 16 and 17, Fig. 12) contains sedimentary structures indicative of fluid flow (water), likely resulting from increased precipitation within the basin as a function of decreased variation in insolation relative to Units 6, 9, 13. The soil that formed preserves many sediment-filled, clay-lined roots, indicating the soil was well- drained. Low amplitude (variability) of higher order Milankovitch cycles allows for the precessional cycle to be the dominant control on climate, and thus the middle VHG represents the greatest stability of insolation in my section as indicated by deep lake facies. The upper VHG could be the result of slightly more variable insolation.

However, it is important to point out that orbital forcing is not the only factor affecting lake depth and soil formation. Subsidence rates, drainage patterns, and amount of sedimentation all contribute to the facies variations seen in the Newark Basin.

5.7 Modern-Day Comparisons

Modern examples of rift basin lakes are found around the world. Smoot and

Olsen (1988) used the East African Rift Valley Lakes (Fig. 2) as comparisons to the

Triassic rift valleys of North America. These modern rift basin lakes exhibit the same elongate shape as seen in the Triassic rifts due to divergent tectonic forces (Schlische,

1993; Smoot and Olsen, 1994; Harris et al., 2013). Carbonate deposition has been observed in these lakes, which are balanced-filled most of the year, with an outlet

64 maintaining constant lake level. Carbonate deposition is thought to be facilitated, at least in part, by hydrothermal activity (Harris et al., 2013). Stromatolites and thrombolites are found above current lake levels, indicating that the lakes were deeper than at present

(Gerilowski-Kordesch and Park, 2004; Harris et al., 2013). Only algal mats are found in my section; domal stromatolites can be found approximately 30 meters higher in my study site.

5.8 Implications

This is the first known study to document paleosols in the Newark Basin and presents evidence that suggests the degree of soil development within VHGs is inversely related to the degree of VHG development. That is, VHGs containing deep lake facies are associated with poorly developed paleosols (Fig. 12, Unit 19) which contain diagenetically-filled root traces and lack translocated clay. Well-developed paleosols

(Fig. 12, Unit 16 and, to a lesser extent, Unit 28) show evidence of translocated clay and contain sediment-filled root traces.

Lake depth is controlled by the amount of net precipitation received by the basin, which is controlled by perturbations in orbital forcing. Climate has an indirect effect on pedogenesis, as it is affected by orbital forcing, by influencing lake formation

(inundation). The amount of time for pedogenesis is limited by the duration of the VHC.

Proximity to the bounding fault complex may affect the degree of soil development.

However, the paleocatenary relationships of soil development have yet to be determined.

My study provides a starting point for additional research and testing of this hypothesis.

Further study is required to determine how each of the perturbations ‘line up’ with my stratigraphic section in order to better predict how orbital forcing manifests itself in the rock record as paleosols.

CHAPTER 6

CONCLUSIONS

Paleosols in this section are overall poorly developed, and are similar to Entisols

(Soil Survey Staff, 2010) or Protosols (Mack et al., 1993). Although weakly developed, differences in the relative degree of development are present, and can be used to provide an overall assessment of the link between pedogenesis and the expression of VHCs.

Paleosols in well-expressed VHGs (Unit 19) were less developed, while paleosols in poorly-expressed VHGs (Unit 16) were more developed. This suggests a negative relationship between the degree of expression of VHGs and soil development. That is, well-expressed VHGs will be associated with more poorly developed soils. The five factors of soil formation had different amounts of influence over the three soils that developed in the lower, middle, and upper VHGs (Fig. 12). Parent material had little effect on the development of these paleosols since it was the same for all three, with the exception of the metamorphic terrane in Unit 19 (Fig. 15), throughout the section.

Organisms had little influence on pedogenesis. Burrows slightly altered the soil fabric, while roots provided a conduit for clay translocation. Climate did not have sufficient time to noticeably affect these paleosols. If the climate that was dominant at the time

Unit 16 was pedogenically modified was significantly different than that of Unit 28 , there would be very little evidence for this (if any) preserved due to the limiting factor of time.

Climate, time, and lake level are interrelated controls on pedogenesis. Lake level is affected by climate, which is affected by amount of insolation, which in turn is influenced by perturbations in Earth’s orbit. The amount of time between VHCs is fixed

67 at ~21 kyr (Van Houten, 1964; Olsen, 1986a), which is sufficient to induce significant pedogenic alteration. Thus, the ultimate control on soil development in this section is time as a function of orbital forcing and the degree of pedogenic alteration that could be induced before the next lake was established. However, it is unclear what proportion of the ~21 kyr cycle was reserved for pedogenesis. Independent of orbital forcing, relief likely had the most control over pedogenesis throughout the Basin. Soils that formed more distal to the bounding fault complex may not have been subject to inundation by lakes due to a higher elevation. Further study into paleocatenary relationships of soil development is necessary to corroborate these interpretations.

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APPENDIX A. X-RAY FLUORESCENCE INSTRUMENT ERROR BASED ON BHVO ANALYSES

Element Standard Error (±) % Relative Standard Deviation SiO 2 0.05 0.10 TiO 2 0.01 0.19 Al 2O3 0.02 0.14 MgO 0.01 0.10 CaO 0.009 0.08 Na 2O 0.004 0.20 K2O 0.001 0.29 P2O5 0.001 0.36 Sr 3.88 ppm 1.0 Y 0.3 ppm 1.2 Zr 2 ppm 1.2 Ni 1 ppm 0.6 Cr 10 ppm 3.0 Nb 0.4 ppm 2.6 Cu 3.7 ppm 2.9 Zn 0.5 ppm 0.6 Ba 7.6 ppm 6.6 Modified from Franklin and Marshall (2013).

APPENDIX B. COMPOSITION OF SAMPLES FROM PALEOSOLS AND LACUSTRINE SEDIMENTS IN WEIGHT PERCENT OF OXIDES AND MINOR ELEMENTS (PPM)

Sample SiO 2 TiO 2 Al 2O3 MgO CaO Na 2O Unit 28, 70 cm 61.87 0.74 14.29 4.41 6.21 3.45 Unit 28, 45 cm 61.37 0.82 15.81 2.56 4.80 5.11 Unit 28, 5 cm 61.45 0.90 17.93 2.56 1.50 4.03 Unit 21, 20 cm 54.37 0.66 17.41 5.44 5.26 5.03 Unit 19, 102 cm 56.35 0.75 15.05 4.92 10.03 3.50 Unit 19, 10 cm 56.35 0.82 17.36 2.12 2.67 3.17 Unit 17, 95 cm 72.28 0.91 13.84 0.92 0.35 4.97 Unit 16, 52 cm 63.33 0.89 16.70 1.96 3.48 4.90 Unit 16, 42 cm 62.84 0.89 16.72 1.79 3.15 5.35 Unit 16, 10 cm 58.68 0.89 17.19 2.81 5.36 3.76

Sample K2O P2O5 Fe2O3T MnO Total Unit 28, 70 cm 3.27 0.14 5.04 0.23 99.65 Unit 28, 45 cm 2.58 0.13 6.10 0.10 99.38 Unit 28, 5 cm 4.11 0.14 6.85 0.06 99.53 Unit 21, 20 cm 3.01 0.33 8.36 0.14 100.01 Unit 19, 102 cm 2.70 0.20 5.86 0.16 99.52 Unit 19, 10 cm 4.27 0.13 7.02 0.04 99.63 Unit 17, 95 cm 1.72 0.14 4.87 0.08 100.08 Unit 16, 52 cm 2.62 0.17 5.68 0.14 99.87 Unit 16, 42 cm 2.46 0.16 6.57 0.13 100.06 Unit 16, 10 cm 3.39 0.16 7.10 0.10 99.44

Sample Rb Sr Y Zr Ni Cr Cu Unit 28, 70 cm 103 289 41.3 297 36 86 8 Unit 28, 45 cm 85.3 325 29.8 249 35 110 7 Unit 28, 5 cm 156 219 31.2 242 44 120 8 Unit 21, 20 cm 96.4 435 20.1 124 41 117 5 Unit 19, 102 cm 84.3 391 31.3 190 33 100 4 Unit 19, 10 cm 165 210 27.8 286 42 131 7 Unit 17, 95 cm 64.4 149 36.4 285 25 115 8 Unit 16, 52 cm 99.7 208 36.1 297 38 135 15 Unit 16, 42 cm 90 223 41 260 34 125 7 Unit 16, 10 cm 122 216 36.3 365 39 120 5

Sample Zn Co Ba La Ce U Th Unit 28, 70 cm 108 18 583 35 76 3.5 10.4 Unit 28, 45 cm 74 17 421 32 73 2.4 7.8 Unit 28, 5 cm 90 23 611 37 80 3.3 17.8 Unit 21, 20 cm 175 28 415 29 65 1.2 4.6 Unit 19, 102 cm 124 21 365 24 64 4.0 6.4 Unit 19, 10 cm 84 21 535 37 94 1.7 18.4 Unit 17, 95 cm 49 15 514 35 68 4.7 18.1 Unit 16, 52 cm 120 19 509 34 76 2.4 12.0 Unit 16, 42 cm 72 19 488 33 84 2.9 18.5 Unit 16, 10 cm 103 23 527 34 80 1.0 11.1

APPENDIX C. MAGNETIC SUSCEPTIBILITY DATA

Distance Reading 58 119.71 126 126.98 -6 from x 10 60 110.44 128 113.80 bottom (cgs) 62 94.58 130 178.57 of 64 146.79 132 139.54 section (cm) 66 137.57 134 99.23 68 145.50 136 110.48 0 22.52 70 154.07 138 49.60 2 33.73 72 126.31 140 125.68 4 62.86 74 131.61 142 61.55 6 45.01 76 98.51 144 93.27 8 39.69 78 89.95 146 93.94 10 31.13 80 115.74 148 17.85 12 50.93 82 112.40 150 19.20 14 51.58 84 115.73 152 27.13 16 62.17 86 92.55 154 21.20 18 43.02 88 95.24 156 80.67 20 60.21 90 94.55 158 162.72 22 82.70 92 124.33 160 134.26 24 54.90 94 140.87 162 162.71 26 37.66 96 99.21 164 85.36 28 62.18 98 65.44 166 181.21 30 134.87 100 110.45 168 64.80 32 115.73 102 132.86 170 73.40 34 59.48 104 103.12 172 84.70 36 66.10 106 144.14 174 78.72 38 46.26 108 10.55 176 157.41 40 29.06 110 137.61 178 220.22 42 44.30 112 74.72 180 126.31 44 16.51 114 83.98 182 97.86 46 17.83 116 17.13 184 140.22 48 79.36 118 208.31 186 132.94 50 83.33 120 136.88 188 107.82 52 158.03 122 154.74 190 126.34 54 55.54 124 107.76 192 111.74 56 54.88

194 133.59 270 151.44 346 286.33 196 158.09 272 126.98 348 162.65 198 170.63 274 175.25 350 60.80 200 134.90 276 154.09 352 153.46 202 185.83 278 181.87 354 82.66 204 152.09 280 177.20 356 74.06 206 128.95 282 109.76 358 142.22 208 151.42 284 189.10 360 72.72 210 121.69 286 34.39 362 76.05 212 163.97 288 120.98 364 130.30 214 142.15 290 109.08 366 122.38 216 129.58 292 149.46 368 108.46 218 130.27 294 148.12 370 97.20 220 128.29 296 136.18 372 158.09 222 156.73 298 97.82 374 162.67 224 159.38 300 93.25 376 162.68 226 132.32 302 73.41 378 159.33 228 151.44 304 50.29 380 107.74 230 134.96 306 70.08 382 103.80 232 119.05 308 183.83 384 145.44 234 98.54 310 218.24 386 175.89 236 166.01 312 217.58 388 222.17 238 91.29 314 101.22 390 275.77 240 106.50 316 261.87 392 284.99 242 113.13 318 226.18 394 228.11 244 72.07 320 266.55 396 244.64 246 87.32 322 270.51 398 261.86 248 68.78 324 228.83 400 274.40 250 128.99 326 238.68 402 201.07 252 134.90 328 263.20 404 169.33 254 146.18 330 224.17 406 234.79 256 197.79 332 226.78 408 255.25 258 99.85 334 242.04 410 244.06 260 136.28 336 204.96 412 243.39 262 144.19 338 187.76 414 236.10 264 195.78 340 234.77 416 201.07 266 184.55 342 273.09 418 104.49 268 112.41 344 290.32 420 196.40

422 214.94 498 78.68 30 8.48 424 197.72 500 68.76 32 5.90 426 278.37 502 175.28 34 9.37 428 218.20 504 179.55 36 4.84 430 252.57 506 163.34 38 1.90 432 277.70 508 152.79 40 8.21 434 281.07 510 174.59 42 4.26 436 154.71 512 159.40 44 7.21 438 74.68 514 162.67 46 8.53 440 115.74 516 136.23 48 5.00 442 58.84 518 182.50 50 5.64 444 152.11 520 126.95 52 6.47 446 112.41 522 107.77 54 7.90 448 175.88 524 98.56 56 5.79 450 153.40 526 79.98 58 8.31 452 200.38 60 5.37 454 277.07 Units 19-21 62 5.95 456 159.37 Distance Reading 64 2.79 -6 458 97.90 from x 10 66 6.37 460 152.76 bottom (cgs) 68 6.58 of 462 56.89 section 70 5.11 464 77.37 (cm) 72 6.00 466 90.58 74 6.53 468 169.30 0 11.21 76 5.47 470 152.11 2 7.90 78 5.95 472 117.71 4 8.84 80 4.89 474 103.83 6 9.58 82 5.21 476 150.78 8 5.31 84 10.58 478 150.12 10 7.58 86 10.05 480 222.20 12 6.47 88 6.94 482 68.09 14 6.48 90 11.41 484 78.01 16 8.95 92 10.05 486 66.80 18 10.31 94 7.58 488 162.67 20 6.95 96 4.26 490 146.17 22 9.58 98 3.50 492 113.08 24 6.69 100 7.73 494 128.25 26 10.16 102 5.78 496 56.89 28 8.16 104 8.05

106 3.90 182 12.79 10 11.00 108 5.73 184 18.31 12 8.53 110 3.15 186 11.79 14 8.37 112 4.74 188 14.26 16 3.74 114 9.37 190 15.63 18 4.21 116 5.47 192 18.16 20 7.52 118 7.84 194 17.06 22 5.00 120 6.58 196 15.47 24 9.11 122 7.58 198 15.11 26 10.79 124 6.05 200 12.79 28 13.05 126 4.15 202 14.05 30 12.94 128 6.58 204 14.32 32 9.57 130 13.37 206 14.53 34 10.10 132 10.63 208 15.26 36 9.47 134 18.79 210 13.95 38 8.79 136 15.00 212 10.16 40 8.42 138 15.53 214 14.79 42 6.68 140 11.68 216 17.58 44 8.00 142 11.05 218 18.84 46 6.79 144 16.84 220 16.48 48 7.48 146 13.00 222 20.21 50 6.00 148 7.63 224 17.84 52 6.21 150 11.11 226 16.06 54 5.63 152 21.69 228 16.21 56 6.79 154 16.21 230 14.58 58 5.95 156 15.10 60 7.48 158 9.89 Units 28-30 62 6.89 160 16.00 Distance Reading 64 7.90 -6 162 16.10 from x 10 66 7.32 164 14.32 bottom (cgs) 68 7.10 of 166 14.68 section 70 9.27 168 12.63 (cm) 72 4.53 170 13.31 74 6.69 172 14.00 0 14.26 76 5.90 174 15.63 2 5.00 78 5.00 176 13.95 4 4.11 80 2.74 178 17.00 6 12.74 82 5.05 180 17.47 8 11.42 84 3.48

86 2.06 162 12.47 88 3.27 164 12.79 90 3.37 166 10.16 92 1.05 168 4.63 94 1.42 170 1.58 96 7.74 172 7.32 98 2.95 100 4.37 102 6.32 104 5.84 106 5.84 108 5.37 110 6.79 112 2.63 114 3.47 116 5.69 118 2.32 120 7.47 122 4.84 124 9.15 126 11.52 128 9.05 130 6.52 132 5.68 134 19.20 136 10.63 138 12.26 140 14.78 142 11.89 144 13.37 146 12.74 148 11.00 150 19.58 152 16.74 154 17.37 156 11.68 158 19.42 160 11.32