344 J. Paleont., 82(2), 2008, pp. 344–350 Copyright  2008, The Paleontological Society 0022-3360/08/0082-344$03.00 THE FIRST UPPER TRIASSIC SILICIFIED HYPERCALCIFIED SPONGES FROM THE ALEXANDER TERRANE, GRAVINA ISLAND AND KEKU STRAIT, SOUTHEAST ALASKA BABA SENOWBARI-DARYAN, 1 ANDREW H. CARUTHERS, 2 AND GEORGE D. STANLEY JR. 2 1 Institut fu ¨r Pala ¨ontologie, Loewenichstr. 28, D-91054 Erlangen, Germany, basendar@pal.unierlangen.de and 2 The University of Montana Center for Paleontology, Missoula 59812, george.stanley@umontana.edu ABSTRACT—This paper describes the first silicified Upper Triassic (Early Norian) hypercalcified sponges known from the Alexander terrane, southeast Alaska. Sponges consist of five taxa from the Cornwallis Limestone of Keku Strait, southeast Alaska: Amblysiphonella Steinmann, Parauvanella Senowbari-Daryan and Di Stefano, Nevadathalamia cylindrica (Seilacher), N. minima n. sp., and Stellispongia (S. cf. subsphaerica Dieci, Antonacci, and Zardini). The hypercalcified sponges of the Alexander terrane as described in this paper provide paleogeographic linkage with other far-flung terranes of western North America, namely the Western Great Basin of Nevada, Stikinia of the Yukon, as well as the Antimonio terrane of northwestern Mexico. In addition, Parauvanella cf. ferdowensis is known from the Upper Triassic Nayband Formation, Iran. Finally Stellispongia cf. subsphaerica is known from the Upper Carnian Cassian Formation of the Dolomite Alps. Sponges (particularly hypercalcified inozoans, sphinctozoans, chaetetids, and sponge-like organisms) are known worldwide from many Upper Triassic reef and nonreef sites. Although Upper Triassic deposits within the Cordilleran terranes and cratonal North America do not typically contain reeflike buildups, hypercalcifying sponge-like organisms were noted as occurring as part of the intricate paleoecological structure within a biostrome along the western shoreline of Gravina Island, southeast Alaska (southern Alexander terrane). This is in contrast to Keku Strait, southeast Alaska (central Alexander terrane), where hypercalcified sponges were identified from limestone beds within nonreef deposits. INTRODUCTION D URING THE Late Triassic in the former Tethys region, reefs were dominated by scleractinian corals and calcified spong- es during a time of warm global climate and higher sea levels (Stanley, 2001; Flu ¨gel, 2002). Along with scleractinian corals, hypercalcified (=coralline) sponges, including inozoans, sphinc- tozoans, chaetetids, and spongiomorphids, are the dominant con- stituents of Upper Triassic (especially Norian–Rhaetian) reefs. Most importantly, these reefs yield high diversities of hypercal- cified sponges, particularly sphinctozoans. They are known from numerous localities throughout the world, in particular the Tethys seaway, Cordilleran terranes, and cratonal North America (Pan- thalassan Ocean). Western Tethys localities include Austria, north- ern Italy, Hungary, and Slovenia in the Alps (Flu ¨gel, 1981, 2002; Flu ¨gel and Senowbari-Daryan, 2001); the southern Tethys from Sicily (Senowbari-Daryan, 1980, 1990; Senowbari-Daryan and Scha ¨fer, 1986), Turkey (Senowbari-Daryan, 1994a), and Oman (Bernecker, 1986); the northern Tethys at Caucasus (Moissev, 1944; Boiko et al., 1991); central Tethys (Iran: Senowbari-Dar- yan, 1996, 2005a, 2005b; Senowbari-Daryan et al., 1997); and eastern Tethys (Wilckens, 1937; Ro ¨hl et al., 1991). Reefs and reef-related deposits dominated by sponges and cor- als also developed during the Late Triassic in North America. With the exception of occurrences of patch reefs in the Williston Basin of western Canada (Zonneveld et al., 2002), the majority of Upper Triassic reefs occur in the collage of Cordilleran terranes (Stanley, 1996). Many of these reef and reeflike deposits were associated with island-arc terranes of the ancient Panthalassan Ocean, and some were associated with the craton of western North America, including Nevada (Stanley, 1979; Senowbari- Daryan and Stanley, 1992), Oregon (Senowbari-Daryan and Stan- ley, 1988), the Stikine terrane of western Canada (Senowbari- Daryan and Reid, 1987), the Quesnel terrane of western Canada (Stanley and Senowbari-Daryan, 1999), the Antimonio terrane of Sonora, Mexico (Stanley et al., 1994; Goodwin and Stanley, 1997; Senowbari-Daryan et al., 2001), and a few localities from the South American craton (Rauff, 1938; Senowbari-Daryan, 1994b). A complete list with the stratigraphic range and geographic dis- tribution of all sphinctozoan genera and species, known until the end of 2000, is given by Senowbari-Daryan and Garcia-Bellido (2002). Originally located within the Panthalassan Ocean, the Alexan- der terrane (Caruthers and Stanley, in press, fig. 1) is thought to have existed as an ancient volcanic island-arc system, and is cur- rently recognized as being one of many displaced terranes com- prising the Cordilleran region of western North America and Can- ada (Coney et al., 1980). Previous lithological and stratigraphical analysis has revealed a variety of volcanic and sedimentary rock units ranging from Cambrian through Middle Jurassic age with variable Upper Triassic carbonate systems surrounding them (Gehrels and Saleeby, 1987; Gardner et al., 1988; Stanley, 1993; Soja, 1996). Recent and ongoing research from the Alexander terrane has revealed 1) detailed biostratigraphy of Paleozoic to Triassic units in the Keku Strait area, using newly acquired co- nodont data (Katvala and Stanley, in press) and 2) comparisons of associated paleontology (specifically scleractinian corals), li- thology, and paleobiogeography of Late Triassic sediments from Gravina Island and the Keku Strait area, Alexander terrane (Ca- ruthers and Stanley, in press). Caruthers and Stanley (in press) further explore the associated paleobiogeography of Late Triassic stratigraphy and faunal composition (specifically scleractinian corals) between the Alexander terrane and adjacent Wrangellia, providing new evidence opposing previous theories of amalgam- ation between these two terranes. This paper serves as an ap- pendage to these contributions by adding a wealth of information pertaining to silicified sponge taxonomy from the Keku Strait area with imperative paleobiogeographic significance. For this reason, detailed descriptions and figures explaining associated lithology, stratigraphy, locality information and previous paleobiogeograph- ic analysis pertaining to the Alexander terrane have been left out. Figures specific to locality information are cited from correspond- ing work. Katvala and Stanley (in press) identify and describe five Late Triassic (ages defined by bivalve, ammonoid and conodont iden- tifications) localities in the Keku Strait area. These localities are recognized as stand-out in Caruthers and Stanley (in press, fig. 6) based on abundances of silicified, well-preserved, shallow-water marine fauna (specifically sponges and sponge-like organisms), occurring within limestone units. Four localities from the Lower Norian Cornwallis Limestone include: 1) Flounder Cove MI 0099 (M ontana I nvertebrate number) (USGS number M1911); 2) Southwest of Kousk Island MI 0074 (M2136); 3) Big Spruce Island MI 0056 (M2135); and 4) Cornwallis Peninsula East MI 0070 (1906). A fifth locality (MI 0087) is exposed along the Gil Harbor mudflat, cropping out in a limestone unit within the Upper Norian to Rhaetian Hound Island Volcanics.