Southern Provenance of Upper Jackfork Sandstone, Southern Ouachita Mountains: Cathodoluminescence Petrology
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Southern provenance of upper Jackfork Sandstone, southern Ouachita Mountains: Cathodoluminescence petrology MICHAEL R. OWEN* \ Department of Geology, University'of Illinois, 245 Natural History Building, 1301 W. Green St, Urbana, ALBERT V. CAROZZI ) Illinois 61801 ABSTRACT Graham and others (1976) compared lithic fragments from sand- stones of the entire Ouachita sequence with those of the Carboniferous of The source ¡irea of the upper Jackfork Sandstone of the southern the Black Warrior basin, and they concluded that both were derived from Ouachita Mountains of Arkansas has been located by means of cath- a source area to the east, in the southern Appalachians. Their study, odoluminescence (CL) of quartz in conjunction with standard however, relied upon 24 selected lithic-rich samples, only three of which petrography. Comparison of frequency distributions of quartz CL col- were from the upper Jackfork. Furthermore, regional stratigraphic studies ors between the Jackfork and approximately coeval sandstones of the (Thomas, 1974; Mack and others, 1981; Mack, 1982) have cast doubt on Black Warrior basin detected genetically based affinities which were a major detrital-sediment-dispersal system linking the southern Appala- not apparent by ¡inspection of gross petrology. chians with the Black Warrior and Ouachita basins. The upper Jackfork was derived from the same source area as The objective of this study was to determine if the upper Jack fork of the Parkwood Formation of the Black Warrior basin of Alabama. The the southern Ouachita Mountains is genetically related to any of the Parkwood is kno wn to have come from the south, and so the Jackfork approximately coeval sandstone units of adjacent basins. If it is, and if the did also. The Jackfork represents a deep-water lithologic equivalent of source area of a related sandstone is already known, then the source area the deltaic and nearshore marine Parkwood, deposited as turbidites in of the Jackfork will have been located. the deeper water of the Ouachita trough. Cathodoluminescence (CL) of quartz in these sandstones provides a statistically valid criterion for comparison which could not be obtai ned by INTRODUCTION conventional petrography. Statistical analysis of frequency distributions of CL colors confirms that the upper Jackfork Sandstone was derived from a The Jackfork Sandstone (Morrowan) is a deep-marine arenaceous source area with the same composition as was the Parkwood Formation of flysch which crops out widely in the Ouachita Mountains of Arkansas and the Black Warrior basin of Alabama, whose source area lay to the south- Oklahoma (Cline, 1970; Morris, 1971). It consists of a thick sequence of west (Thomas, 1974). Further examination of the two units affords insight moderately well sorted, medium- to fine-grained, indistinctly graded sand- into the nature of the southern orogenic belt which provided sediment to stone, alternating with shale or silty shale, in laterally persistent beds. form both units. Jackfork sediments were deposited as turbidites in a complex array of submarine fans, part of a much thicker middle and late Paleozoic sequence REGIONAL GEOLOGY of detrital units adjacent to the southern margin of North America (Briggs, 1974; Morris, 1974; Briggs and Roeder, 1978). The Ouachita basin, which extended from western Alabama through Early field workers proposed that the thick Carboniferous portion of Arkansas to west Texas (Thomas, 1977a), was a deep-marine trough from the Ouachita sequence was derived from a now-buried land mass to the pre-Mississippian through Early Pennsylvanian time (Cline, 1970). Ap- south, named "Llnnoria" (Miser, 1921). Subsequent authors have debated proximately 6,500 m of sandstone and shale (with minor chert, tuff, and the question; some favor a northern, cratonic source for much of the olistostromal carbonates) were deposited mainly as a system of submarine sediment (Klein, 1966; Morris, 1971; Pryor and Sable, 1974), whereas fans in the elongate basin (Morris, 1974; Niem, 1976). Sole marks on Morris (1974) and Thomas (1976) have suggested a southerly source for turbidites reveal a consistent westward paleocurrent flow, parallel to the some of the Jackfork of the southern Ouachitas. The controversy con- basin's long axis (Morris, 1977a, 1977b). They do not, however, unequiv- tinues because (1) regional trends in grain size or bed thickness which ocally indicate the proximate source of the sediment, because present might directly indicate the source of the sediment are indeterminant due to exposures represent only the deep, axial portion of the basin (Morris, structural and stratigraphic uncertainty; (2) sole marks on turbidites indi- 1974; Graham and others, 1975), and turbidite sole marks often reflect cate flow direction, not source area; and (3) attempts to use petrologic along-axis paleoflow directions even if sediment supply was actually from variability within the Jackfork for provenance determination have met the sides of the basin (Bouma, 1962; Stanley and Bouma, 1964). with only limited success (Klein, 1966; see Morris, 1971). Sandstones of the Black Warrior and Illinois basins are candidates for sharing a genetic affinity with the Jackfork because they have approxi- •Present address: Department of Geology, St. Lawrence University, Canton, mately equivalent ages (Fig. 1), similar quartzose-lithic mineralogy, and New York 13617. dispersal patterns which may have included the Ouachita basin. The shal- Geological Society of America Bulletin, v. 97, p. 110-115,4 figs., 2 tables, January 1986. 110 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/1/110/3444983/i0016-7606-97-1-110.pdf by guest on 30 September 2021 CATHODOLUMINESCENCE PETROLOGY, OUACHITA MOUNTAINS 111 low shelf north of the Ouachita basin was dominated by carbonate and was open to the south, in the direction of the Ouachita basin, until the end minor siliciclastic sedimentation at this time and is not considered a likely of the Paleozoic (Buschbach and Atherton, 1979). Subsequent uplift of the source for the Jackfork of the southern Ouachitas. Pascola arch, however, has removed evidence of possible linkage of the In the Black Warrior basin, two thick fluvial-deltaic to shallow- two basins. marine clastic wedges, one derived from the southwest and the other from the northeast, converged during Late Mississippian and Early Pennsylva- SAMPLE COLLECTION nian time (Davis and Ehrlich, 1974; Hobday, 1974; Thomas, 1974; Mack and others, 1983). The Parkwood Formation was part of the southwest- A total of 228 thin sections was examined in this study. Of these, 145 derived wedge (Mack, 1982), whereas the overlying Pottsville Formation were prepared from samples collected at the 300-m-thick DeGray Dam resulted from mixed sediments originating from separate sources to the Spillway section near Arkadelphia, Arkansas (see Stone and others, 1973). southwest, northeast, and southeast (Horsey, 1981; Rheams and Bensen, Parkwood (27) and Pottsville (16) samples were collected from outcrops 1982). The southwestern source area for the Parkwood and part of the and roadcuts in and near Birmingham, Alabama. From the Illinois basin, Pottsville was an orogenic highland composed of mostly low-grade meta- 29 samples were collected from Chesterian sandstone units, along with 11 morphic and sedimentary rocks with a minor volcanic component (Davis samples of the Morrowan Caseyville Formation. and Ehrlich, 1974; Mack and others, 1981,1983). Although its exact stratigraphic position is unknown due to the ab- In the Illinois basin, — 1 km of shallow-marine and deltaic Mississip- sence of diagnostic fossils, the DeGray Spillway section is believed to pian sediments are overlain by Lower Pennsylvanian fluvial sandstone and represent a narrow stratigraphic interval in the lower part of the upper conglomerate, with a major erosional unconformity between them (Will- Jackfork. It is —520 m beneath the upper Morrowan Johns Valley Shale man and others, 1975). Sediment supply into the shallow Illinois basin (Stone and others, 1984) and thus probably of mid-Morrowan age. In the was mainly from the northeast via a large network draining the Canadian Black Warrior basin, the Parkwood Formation spans the Mississippian- Shield (Siever and Potter, 1956; Bristol and Howard, 1974). The basin Pennsylvanian boundary (Thomas, 1976). The Pottsville Formation near Figure 1. Partial stratigraphic column of the three basins discussed in the text. Time-stratigraphic relations between the largely unfossiliferous Ouachita and Black Warrior basins are not definite (after Pryor and Sable, 1974, and Thomas, 1977). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/97/1/110/3444983/i0016-7606-97-1-110.pdf by guest on 30 September 2021 112 OWEN AND CAROZZI Birmingham is of middle to late Morrowan age. Samples for this study ing because Jackfork, Parkwood and Pottsville, and Illinois basin ¡sand- were taken mainly from the upper Parkwood and lower Pottsville, such as stones are mostly quartz arenite with relatively minor amounts of other is exposed along Green Springs Highway in Birmingham (see Owen, detrital components. Each sandstone contains a small and generally varia- 1984, for details of sampling sites). In the Illinois basin, samples were ble amount of lithic fragments, but in most samples, their abundano; and collected throughout the Chesterian sequence and near the unconformable diversity are too low to reveal significant genetic relationships. The Park- contact