search.noResults

search.searching

note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
696


Journal of Paleontology 89(5):695–729


the permineralized microbes, the composition of the fossil- permineralizing, -infilling, and -encrusting minerals and enclosing matrix, and that suggest a new way to infer the oxic/ anoxic nature of the fossil-preserving environment.


Geology of the Maly Karatau Range (South Kazakhstan) Geographic and stratigraphic setting.—The Maly Karatau Range (Fig. 1.1) is located within the Karatau-Таlass folded zone of the Ulutau-Sinian structural belt that extends south- eastward from the Ulutau Mountains of central Kazakhstan into northern China. The basinal sediments that comprise this monocline (Fig. 1.2), deposited during the Caledonian tectonic cycle, span an interval that extends from the Neoproterozoic to the mid-Paleozoic. The Neoproterozoic (Upper Riphean) to Lower Cambrian part of this succession includes six stratigraphic groups, defined and discussed in detail in numerous publications (Bezrukov, 1941; Аnkinovich, 1961; Korolev, 1961, 1971; Keller et al., 1965; Krylov, 1967; Eganov and Sovietov, 1979; Korolev andOgurtsova, 1981, 1982; Missarzhevskii andMambetov, 1981; Ogurtsova, 1985; Eganov et al., 1986; Ogurtsova and Sergeev, 1987, 1989; Missarzhevskii, 1989; Sergeev, 1989, 1992, 2006; Sergeev and Ogurtsova, 1989; Mambetov, 1993; Popov et al., 2009; Meert et al., 2011). The source of the Lower Cambrian Kyrshabakta and Chulaktau microbiotas studied here is the uppermost of the six stratigraphic units, the Ediacaran through Ordovician Tamda Group. The Tamda Group is composed of three formations:


the lowermost terrigenous-carbonate 6- to 300-m thick Kyrshabakta Formation, characterized by basal diamictites (the “Aktas tillites”; Meert et al., 2011) and an overlying carbonate unit containing interbedded microfossiliferous chert lenses that has been referred to as the “Lower Dolomite” or “Berkuta Formation” (Korolev, 1971) or the “Berkuta Member” (Missarzhevskii and Mambetov, 1981); the mid- Tamda Group siliceous-phosphate Chulaktau Formation, up to a few tens of meters in thickness; and the >3000-m- thick uppermost carbonate Shabakta Formation. For clarity, we refer to the post-glacial carbonate unit of the lowermost Tamda Group Kyrshabakta Formation, the source of one of the two fossil assemblages described here, as the “Berkuta Member.” As discussed by Meert et al. (2011), deposition of the


lowermost, pre-Berkuta part of the Kyrshabakta Formation commenced with sedimentation of the ~30-m thick Aktas tillites, a unit that was then overlain by a massive widespread cap-dolomite that ranges from 1–3to10–12m thick (Eganov and Sovietov, 1979; Eganov et al., 1986). Separated by a hiatus from the cap-dolomite, deposition continued by sedimentation of a fine-grained dolomite that, in turn, was overlain by a mixed terrigenous and brownish carbonate succession documented only along the Kyrshabakata River (viz., at outcrop K-28 of the present paper). In most of the stratigraphic sections studied here—viz., the Koksu (outcrop K-27), Berkuta (K-29), Au-Sakan (K-30), Zhaanaryk (K-32), Aktogai (K-33), and Kurtlybulak (K-40) sections (Fig. 2)—the lower (pre-Berkuta) part of formation is represented either by interbedded siltstones and argillites or is missing from the succession with a 6–8m


thick part of the Berkuta sediments directly overlying tuffs of the immediately underlying Neoproterozoic Kurgan Formation of the Maly Karoy Group. The Berkuta Member of the Kyrshabakta Formation—


strata assigned by Eganov and Sovietov (1979) to the overlying Chulaktau Formation—is composed predominately of dolostone augmented by microfossil-bearing nodules of phosphorite and chert, and contains problematic stromatolites, thrombolites, and metazoan burrows. Following the suggestion of Missarzhevskii and Mambetov (1981) and Missarzhevskii (1989), we regard this microfossiliferous unit—which unconformably overlies older rocks, primarily those of the Maly Karoy Group—as the terminal member of the Kyrshabakta Formation. Sequence stratigraphy indicates that the Berkuta Member and overlying strata of the formation represent a transgressive sequence that decreases in thickness toward the Besh Tash stratigraphic section along the Tian Shan Mountains (outcrop #9 in Missarzhevskii and Mambetov, 1981) to the southeast of the sections sampled here (Fig. 1). The Lower Cambrian Chulaktau Formation conformably


overlies the Kyrshabakta Formation and the slightly eroded surface of its uppermost Berkuta Member. Silicified phosphor- ites of the Chulaktau occur as reentrants infilling cracks and erosional features at the top of the Berkuta Member and as phosphatic breccias and interclastic grainstones (flat-pebble conglomerates). Traditionally, the Chulaktau Formation has been divided


into three subunits, in ascending order the Aksai, Karatau, and Ushbass Members (Missarzhevskii and Mambetov, 1981; Mambetov, 1993; Popov et al., 2009). The Aksai (known also as the “Cherty Member”), a few centimeters to a few meters in thickness, is composed of silicified and non-silicified oolitic phosphorites interbedded with dolomites, shales and bedded cherts and contains abundant thrombolites, in some areas forming reef- or bioherm-like bodies. As documented here, silicified rocks of this unit are richly microfossiliferous. The middle, Karatau Member of the formation—up to tens


of meters thick and composed mainly of nonsilicified or partially silicified (and sporadically microfossiliferous) phos- phorites interbedded with shales, cherts, and dolomites—is the principal phosphate-producing unit of the succession. Because of its economic importance, the predominantly oolitic and coarse-grained phosphorites of this unit have been described in numerous publications (e.g., Eganov and Sovietov, 1979; Baturin, 1978; Kholodov and Paul, 1993a, 1993b, 1994). In the traditional stratigraphic scheme, the immediately


overlying iron and manganese oxide-rich limestones and limy dolostones of the Ushbass Member—having a maximum thickness of ~3m and present sporadically throughout the Maly Karatau Range—have been regarded to comprise the uppermost unit of the Chulaktau Formation. Ushbass strata are overlain disconformably by cherty dolomites of the >3000-m thick Early Cambrian (Atdabanian Stage) through the Ordovician Shabakta Formation. Opinions vary regarding the stratigraphic boundary


between the Shabakta and Chulaktau formations (e.g., Eganov and Sovietov, 1979; Eganov, 1988; Meert et al., 2011). Here, we follow Missarzhevskii and Mambetov (1981), who assign the Ushbass Member to the Shabakta Formation rather than the


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212