Caruthers et al. Utility of organic carbon isotope data from the Salina Group halite (Michigan Basin): A new tool for stratigraphic correlation and paleoclimate proxy resource Andrew H. Caruthers1,†, Darren R. Gröcke2, Stephen E. Kaczmarek1, Matthew J. Rine1, Jeff Kuglitsch3, and William B. Harrison III1 1Department of Geological and Environmental Sciences, Western Michigan University, 1903 West Michigan Avenue, Kalamazoo, Michigan 49008-5241, USA 2Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK 3 Department of Earth Sciences, North Carolina Wesleyan College, 3400 North Wesleyan Boulevard, Rocky Mount, North Carolina 27804-9906, USA ABSTRACT INTRODUCTION In this study, we used a multiproxy data set 13 13 approach. Local δ Ccarb and δ Corg records de- Long-term global carbon isotope records Evaporative basins are an integral part of sci- rived from normal marine carbonate and halite- 13 13 (δ Ccarb and δ Corg) for the Silurian have ence and society. They provide reservoir seals prone deposits in the Silurian Michigan Basin been largely derived from unrestricted open- for over half of the world’s petroleum reserves (Fig. 1) were compared to an established global marine carbonates and shales. Here, we (Sarg, 2001, and references therein), and they inorganic carbon isotope curve in order to es- demonstrate how organic carbon harvested are commonly mined for a variety of manu- tablish depositional age constraints for the onset from halite-dominated evaporite deposits in facturing and industrial applications (Warren, of halite deposition. During deposition, organic a restricted intracratonic basin can be used 2016). In an academic sense, large halite-domi- matter was trapped and preserved as inclusions to produce a carbon isotope record. Inor- nated evaporative basins are especially impor- within the halite (Fig. 1D). By collecting this ganic and organic carbon isotope data were tant because they provide a potential rare link organic material at regular intervals, it should generated and compared from four subsur- among the ancient atmosphere, hydrosphere, be possible to produce a long-term geochemical face cores from the Silurian Michigan Basin, and lithosphere during long-term paleoclimate record for the basin. The Salina Group halite of representing unrestricted carbonate and re- change (e.g., Fanlo and Ayora, 1998; Warren, the Michigan Basin is an ideal candidate with stricted evaporite/carbonate deposition. The 2016). However, in order to assess the poten- which to test this approach, because it is thought 13 13 δ Ccarb and δ Corg records exhibit a number tial effects of prolonged evaporation on the to be structurally intact and it does not display of long-term trends and major carbon iso- local paleo environment, it is necessary to first large-scale doming, or postdepositional salt mi- tope excursions (CIE) that are correlated constrain the depositional timing of large-scale gration (Mesolella et al., 1974; Cercone, 1984). with the globally identified Ireviken, Mulde, evaporation events. and Linde events. These data provide tem- One of the biggest obstacles in halite-prone SILURIAN PALEOCLIMATE poral and stratigraphic constraints in rocks sequences is obtaining reliable age constraint, where paleontological data are sparse or because nearly all biostratigraphically important The Silurian was a period of intense cli- absent. They also potentially highlight the marine organisms are typically absent. In highly matic instability dominated by highly variable effect of enhanced local evaporation on iso- evaporative settings, it is also not possible to rely ocean temperatures, strong swings in eustasy, 13 tope fractionation. This new technique for on inorganic sources, such as δ Ccarb, to com- and frequent biotic turnover (Jeppsson, 1990; generating a long-term organic carbon iso- pare with long-term global trends, because most Samtleben et al., 1996; Azmy et al., 1998; Mun- tope profile from Silurian halite sequences, halites contain very little associated carbonate necke et al., 2003; Kaljo et al., 2003; Lehnert 13 which can be correlated to the global curve, (Warren, 2016). As such, δ Ccarb can, at best, et al., 2010; Noble et al., 2012; McAdams et al., is of broad interest to the geoscience and provide an incomplete isotope record. Without 2017; and others), as evidenced by eight bio- paleo climate science communities. These temporal constraint in evaporite sequences, it stratigraphically constrained carbon isotope ex- data not only provide a valuable tool for is difficult (1) to establish stratigraphic corre- cursions (CIEs; Cramer et al., 2011, 2015, and under standing the chronostratigraphic lations within and outside the basin, and (2) to references therein). From oldest to youngest, framework within an evaporative interior discern the effects of changing global versus these include the early Aeronian, late Aeronian, basin, but they also provide a rare temporal local climate conditions. These challenges be- Valgu, Ireviken, Mulde, Linde, Lau, and Klonk 13 link between periods of prolonged evaporite come surmountable if temporally constrained events. Most CIEs range 2‰ to 4‰ δ Ccarb rela- depo si tion and events of known paleoclimate and uniquely global chemostratigraphic signa- tive to background values, with the Lau event change. tures can be identified within the basin, thereby ranging 7‰ to 12‰. Comparisons of these establishing a means of comparison with the CIEs with small-scale extinction and recovery †andrew .caruthers@ wmich .edu global record. events exhibit variable degrees of correlation, GSA Bulletin; November/December 2018; v. 130; no. 11/12; p. 1782–1790; https://doi .org /10 .1130 /B31972 .1 ; 6 figures; Data Repository item 2018153 ; published online 8 May 2018. 1782 Geological Society of America Bulletin, v. 130, no. 11/12 © 2018 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/130/11-12/1782/4535453/1782.pdf by guest on 29 September 2021 Organic carbon isotope data from halite: A tool for global temporal correlation lying (i.e., tropical) latitudes in the central part B A 60°N of the Laurentian Continental Seaway, which A N was connected to the Iapetus Ocean to the south and the Panthalassan Ocean to the west and K A′ covered much of present-day North America W B Panthalassa (Fig. 1A). During Wenlock (early Sheinwood- 0° ian–Homerian) time, elaborate barrier and pin- M nacle reef complexes developed along the mar- gin and almost completely rimmed the basin s Iapetu (Fig. 1B). This barrier and pinnacle reef system 160 km comprises the upper part of the Niagara Group 60°S (Guelph Formation), which altogether ranges in C D thickness from 39 m (130 ft) to 213 m (700 ft) MICHIGAN BASIN preserved on the basin margin. organics The Niagara barrier and pinnacle reef system is capped by up to 762 m (2500 ft) of interbed- E Mesolella Catacosinos Rine ded anhydrite, halite (Fig. 1D), and organic-rich et al. et al. carbonate mudstone of the Salina Group, repre- AG et al. (1974) (2000) (2017) senting a major change in paleoenvironment and SYSTEM SERIES ST BASS ISLANDS local sea level (Mesolella et al., 1974; Sullivan et al., 2016). The Salina Group is divided into PR N SALINA repeating sequences of evaporites, carbonates, D L SALINA SALINA and shales identified as Salina units A-0 to G LU Go (Mesolella et al., 1974). Within this group, non- NIAG evaporite carbonate and shale units (e.g., A-0, N Ho SILURIA NIAG NIAG A-1C, A-2C, C, E, and G) are known to have WE Sh MAN greater lateral continuity than evaporite-domi- nant units (Mesolella et al., 1974; Harrison and Figure 1. (A, B) Silurian paleogeography and schematic map of the Michigan Basin with Voice, 2017). location of cores at: K (State Kalkaska #2–15); B (Bruske #1–26); W (Weinert #2–6); and Because the primary focus of this study cen- M (DC-Mead #1). Dark-blue circles—locations of pinnacle reefs (from Briggs et al., 1980). ters on the subject of a new global correlation (C) Silurian chronostratigraphies for the Michigan Basin showing discrepancy in deposi- proxy, it is important to briefly discuss some tional timing for Niagara and Salina Groups. PR—Pridoli, LUD—Ludlow, WEN—Wen- confusing terminology in the local (i.e., sub- lock, L—Ludfordian, Go—Gorstian, Ho—Homerian, Sh—Sheinwoodian, NIAG—Niagara, surface Michigan Basin) versus regional (i.e., MAN— Manistique. (D) Precipitated organic matter in halite from the A-2 Evaporite, DC- eastern United States) stratigraphic assignment Mead #1 core at ~190.0 ft (58 m). Scale for D is in cm. of Silurian units. Originally, the term Lockport was designated as a group-level term in the state of New York (Brett et al., 1995; fig. 1in Cramer suggesting that no single repetitive set of offers the potential to assess variation in atmo- et al., 2011), whereas in the Michigan Basin, it is 13 paleo climatic circumstances and/or controlling spheric pCO2 (i.e., changes in ∆ C; e.g., Kump used at the formation level (e.g., formally as the mechanism can explain these events (Munnecke and Arthur, 1999). In a study focusing on the Lockport Dolomite Formation in Catacosinos et al., 2010; Noble et al., 2012; Cooper et al., timing of the “two-prong” Mulde event in Arctic et al., 2000, 2001; or informally as the Lockport 2014; Jarochowska and Munnecke, 2015; Trot- Canada, Noble et al. (2005, 2012) showed vari- Formation). Similarly, the term Niagaran is a re- ter et al., 2016). ability in CIE magnitude not only between adja- gional time designation in North America, tem- 13 Until now, carbon isotope data (δ Ccarb and cent stratigraphic sections, but also between the porally equivalent to the combined Llandovery 13 δ Corg) for the Silurian have been derived pri- organic and inorganic carbon isotope records.