Drainage Reversals in Mono Basin During the Late Pliocene and Pleistocene
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Drainage reversals in Mono Basin during the late Pliocene and Pleistocene Marith C. Reheis* U.S. Geological Survey, M.S. 980, Federal Center, Denver, Colorado 80225, USA Scott Stine Department of Geography and Environmental Studies, California State University, 25800 Carlos Bee Boulevard, Hayward, California 94542, USA Andrei M. Sarna-Wojcicki U.S. Geological Survey, M.S. 975, 345 Middle®eld Road, Menlo Park, California 94025, USA ABSTRACT Basin between the hydrologically distinct vive out of water for even short periods) can Lahontan and Owens±Death Valley sys- expand their range across otherwise insur- Mono Basin, on the eastern ¯ank of the tems, as long postulated by biologists, and mountable drainage divides. Biologists, point- central Sierra Nevada, is the highest of the also con®rms a probable link during the ing to several such species that today occur in large hydrographically closed basins in the Pleistocene for species adapted to travel up- the hydrologically distinct Lahontan and Basin and Range province. We use geo- stream in fast-¯owing water. Owens±Death Valley systems (e.g., Hubbs morphic features, shoreline deposits, and and Miller, 1948; Minckley et al., 1986; basalt-®lled paleochannels to reconstruct Keywords: biogeography, drainage chang- Hershler and Sada, 2002), have long specu- an early to middle Pleistocene record of es, ®sh, Great Basin, Mono Basin. lated that Mono Basin may have linked these shorelines and changing spillways of Lake two systems at some time in the past (e.g., Russell in Mono Basin. During this period INTRODUCTION Hubbs and Miller, 1948; Taylor, 1985). This of time, Lake Russell repeatedly attained study con®rms that linkage and places the altitudes between 2205 and 2280 mÐlevels The Mono Basin abuts the eastern ¯ank of transfer from north to south at sometime after far above the present surface of Mono Lake the central Sierra Nevada (Fig. 1). This young 1.3 Ma and likely after 0.76 Ma. (;1950 m) and above its last over¯ow level structural depression (Gilbert et al., 1968; Pakiser, 1976; Huber, 1981) is the highest of (2188 m). The spill point of Lake Russell Hydrographic Setting shifted through time owing to late Tertiary the large hydrographically closed basins in the and Quaternary faulting and volcanism. Basin and Range province. Mono Lake is the During the early Pleistocene, the lake pe- saline, alkaline remnant of Pleistocene Lake The rim of Mono Basin is much lower on riodically discharged through the Mount Russell, which occupied Mono Basin (Fig. 2). the east than on the north, west, and south. Hicks spillway on the northeastern rim of Throughout much of the Pleistocene the lake This eastern rim is breached in several places Mono Basin and ¯owed northward into the stood at altitudes far above its present surface by low divides, two of which show evidence Walker Lake drainage basin via the East (1958 m in A.D. 1950) and its late Pleistocene of past scouring by lake over¯ow (Fig. 2). The Walker River. Paleochannels recording levels; at times the lake spilled into adjacent lowest divide at present lies in greatly faulted such discharge were incised prior to 1.6 watersheds through gaps in the basin rim. We terrain of the Adobe Hills at an altitude of Ma, possibly between 1.6 and 1.3 Ma, and ®nd that the spill point of Lake Russell shifted 2189±2190 m. This feature, here informally again after 1.3 Ma (ages of basaltic ¯ows through time, and we infer that the shifts were named the ``Adobe Hills spillway,'' is the gap that plugged the paleochannels). Faulting in caused by late Tertiary and Quaternary fault- through which the lake would spill today if it the Adobe Hills on the southeastern margin ing and volcanism (Gilbert et al., 1968; Bailey were to ®ll the basin. A south-draining chan- of the basin eventually lowered the rim in et al., 1976; Metz and Mahood, 1985; Bursik nel heading at this gap carried the last over- this area to below the altitude of the Mount and Sieh, 1989). During the early Pleistocene, ¯ow of Lake Russell into Adobe Valley and Hicks spillway. Twice after 0.76 Ma, and the lake periodically spilled northward into the thence into the Owens±Death Valley system possibly as late as after 0.1 Ma, Lake Russell Lahontan drainage basin; afterward, it spilled (Figs. 1 and 2; Putnam, 1949). discharged southward through the Adobe southward into the Owens±Death Valley sys- Farther north along the east rim of the ba- Hills spillway into the Owens±Death Valley tem of lakes. sin, at the north edge of a small subbasin system of lakes. This study supports a pre- A high-standing basin with shifting spill called Alkali Valley, lies the informally named Pleistocene aquatic connection through Mono points has the capacity to function as a bio- ``Mount Hicks spillway.'' At an altitude of geographic ``switchyard'' through which ob- 2237 m, it stands ;47 m above the Adobe *E-mail: mreheis@usgs.gov. ligately aquatic species (those that cannot sur- Hills spillway. A channel that heads at this GSA Bulletin; August 2002; v. 114; no. 8; p. 991±1006; 9 ®gures; 5 tables; Data Repository item 2002102. For permission to copy, contact editing@geosociety.org q 2002 Geological Society of America 991 REHEIS et al. zone. The concentration of microseismicity in this zone (dePolo et al., 1993) shows that ex- tension is ongoing. Andesitic ¯ows of late Pliocene and Pleis- tocene age cover much of the northeastern margin of the Mono Basin (Fig. 2) in the vi- cinity of the Mount Hicks spillway (Gilbert et al., 1968; Robinson and Kistler, 1986; Lange et al., 1993). These ¯ows are cut locally by north- and northeast-striking faults that are less abundant, shorter, and apparently of less displacement than those in the area of the Adobe Hills spillway (Stewart, 1982). Previous Work Lake Russell/Mono Lake has a well-known late Quaternary history established by Russell (1889), Putnam (1949), Lajoie (1968), and Stine (1987, 1990). About 13 000 yr ago the lake attained its highest level of late-glacial and postglacial time (Lajoie et al., 1982; Ben- son et al., 1990). A conspicuous strandline en- circling the basin marks this highstand at an altitude of 2155 m (Fig. 2), though at places along the Sierran front it has been downfault- ed by as much as 27 m. This shoreline lies 35 m below the Adobe Hills spillway, indicating that the lake has not over¯owed since before 13 000 yr B.P. Discontinuous but conspicuous remnants of a higher shoreline terrace lying at and below an altitude of 2188 m are found at many plac- es around the basin (Figs. 2 and 4A). Such terrace remnants extend into the Adobe Hills Figure 1. Regional map showing extent of late Pleistocene lakes, particularly Lake Russell spillway; the slightly higher apparent altitude in Mono Basin, and over¯ow connections along the eastern Sierra Nevada. of the spillway (;2189±2190 m) is due either to inaccurate contours in the topographic map or to displacement by faults near the spillway (Fig. 3). Putnam (1949), who ®rst noted this gap drains north toward Mud Spring Canyon and interbedded alluvial and lacustrine sedi- terrace and its associated spillway, thought (Fig. 2), a tributary of the East Walker River. ments (Gilbert et al., 1968). that it dated from the time of Tahoe glaciation, Of particular interest to our study are the because he found the terrace on the Tahoe mo- Geologic Setting Pliocene and Pleistocene volcanic ¯ows that raines of June Lake (at Aeolian Buttes, Fig. form the eastern margin of the basin. The area 2). He recognized that Lake Russell over- Mono Basin (Fig. 2) is a southwest-tilted of the Adobe Hills spillway (Fig. 2) is under- ¯owed through a series of shallow basins (Fig. half graben that probably began forming at ca. lain by voluminous ¯ows of olivine basalt lo- 3) into Pleistocene Lake Adobe in Adobe Val- 4±3 Ma (Gilbert et al., 1968; Huber, 1981). cally interbedded with lacustrine and ¯uvial ley. Lake Adobe, in turn, over¯owed into Most of the subsidence is due to displacement deposits. These diatomaceous sands and silts Benton Valley (Fig. 2), a northeastern arm of along the Sierra Nevada frontal fault (Bursik contain abundant fossils of mollusks and ®sh. Owens Valley, by way of a narrow slot cut and Sieh, 1989). The basin is structurally and On the basis of several K-Ar ages, the basalt into granitic rocks of the Benton Range (Fig. topographically closed by a west-trending ¯ows were emplaced between ca. 4 and 3 Ma 4C; Hubbs and Miller, 1948). The late Pleis- monocline on the north, coincident with the (Gilbert et al., 1968; Robinson and Kistler, tocene highstand of Lake Adobe lay at an al- Bodie Hills, and by the north-dipping ¯ank of 1986). The volcanic ¯ows are extensively cut titude of ;1975 m (Fig. 2; Snyder et al., the Long Valley caldera on the south. The gra- by north-striking normal faults and intersect- 1964; Batchelder, 1970). nitic and metamorphic rocks exposed along ing northeast-striking, presumably left-lateral Previous information on ¯uctuations of the Sierra Nevada on the west likely also form faults (Fig. 3). This con®guration has pro- Lake Russell that predate the conspicuous the basement complex beneath Mono Basin. duced a zone of extension and net down-to- shorelines at 2155 m and 2188 m is scant. A These rocks are overlain by a thick accumu- the-south displacement described by Gilbert et driller's log from a wildcat well drilled on lation of Miocene to Holocene volcanic rocks al.