BORINGS IN LARGER BENTHIC FORAMINIFERS FROM TURKEY AND THEIR PALEOENVIRONMENTAL SIGNIFICANCE MUHITTIN GO ¨ RMU ¨ S ¸ 1 AND JAN KRESTEN NIELSEN 2 ABSTRACT Cretaceous/Paleogene outcrops of Turkey provide impor- tant areas for the study of trace fossils on larger benthic foraminiferal tests such as Orbitoides and Loftusia from the Maastrichtian, and Nummulites, Assilina and Discocyclina from the Eocene. The current investigation synthesizes previous and new records of borings on Upper Cretaceous and Paleogene foraminifers with information on faunal associations, stratigraphical correlation and paleoenviron- mental conditions. The types of borings were distributed according to their shallow-water paleoenvironments. Orbitoides tests in siliciclastic sandstones and calcarenites from northwestern and eastern Turkey contain four forms of borings: semicircular tubes, circular cavities, subspherical cavities and undulating tubes. Benthic foraminiferal associa- tions confirm the Maastrichtian age of the borings. Towards the end of the Cretaceous, a regression took place during the Maastrichtian in the Osmaneli area, resulting in a shallower, bivalve-dominated facies. During initial phases of the re- gression, semicircular tubes and circular cavities were formed, while later phases of the regression led to the formation of undulating tubes. The Loftusia tests from southeastern and eastern Turkey contain cylindrical holes, paraboloid pits and subspherical cavities formed as predational and dwelling borings. Borings occur on the Eocene larger foraminifera Nummu- lites, Assilina and Discocyclina from the Ypresian to Bartonian carbonates and siliciclastic sediments in south- western Turkey. These Eocene sediments comprise back-reef, nummulite-bank, fore-reef and open-sea facies. The benthic foraminifers may contain borings such as cylindrical holes, paraboloid pits, subspherical cavities and spiral tubes. The Eocene foraminiferal tests less commonly contain borings and endobiontic foraminifers than those from the Maastrichtian. The Eocene borings were formed in a shallower carbonate setting. INTRODUCTION Studies of larger benthic foraminifers from the Upper Cretaceous and Paleogene of Turkey demonstrate that a variety of borings and encrustations are common at certain stratigraphic levels (Figs. 1–2). Correlation of these levels indicates that the bored tests of larger benthic foraminifers from several localities were bioeroded within different shallow-marine paleoenvironments. Borings as well as fractures and chambers may contain tiny foramini- fers and other microorganisms. These features are partic- ularly seen in Loftusia, Orbitoides, Nummulites and Discocyclina tests (Fig. 3). Among these, the most in- teresting features are different kinds of borings in the tests of Orbitoides, which is a Campanian–Maastrichtian index taxon (Baumfalk and others, 1982; Baumfalk and Nijholt, 1984; Go ¨rmu ¨s ¸ and Sagular, 1998). In addition, an endobiontic foraminifer, probably Talpinella cunicularia, has been observed within the embryonic chambers of Orbitoides (Go ¨ rmu ¨s ¸ and Sagular, 1998). Baumfalk and others (1982) and Baumfalk and Nijholt (1984) reported the first records of T. cunicularia within Orbitoides tests from the early Campanian to late Maastrichtian of southwestern France. Based on the trace fossils of T. cunicularia, Nielsen (2002) described a new ichnotaxon, Curvichnus semorbis. Middle Eocene nummulitids from Afghanistan, Germany, Pakistan (Kaever, 1969) and Italy (Matteucci, 1978) might also have been bioeroded by other foraminifers, algae, clionid sponges and polychaetes. Recently, Meric ¸ and Go ¨ rmu ¨s ¸ (2001) illustrated borings on tests of Loftusia. Although there have been previous studies on fossil and Recent traces, in particular small benthic and planktonic foraminifers (e.g., Sliter, 1971; Arnold and others, 1985; Hallock, 2000; Nielsen and Nielsen, 2001; Nielsen and others, 2003), borings in larger benthic foraminifers are not well documented. To evaluate the paleoenvironmental distribution of the borings, associated filling material and endobiontic organ- isms, we: 1) examined the tests of Orbitoides and Loftusia from Upper Cretaceous siliciclastic sediments and carbo- nates of Turkey, and 2) investigated similar features in Nummulites and Discocyclina tests from Paleogene silici- clastic sediments and carbonates. The borings, endobiontic 1 SDU ¨ Mu ¨ hendislik-Mimarlik Faku ¨ ltesi, Jeoloji Mu ¨ hendislig ˘i Bo ¨- lu ¨mu ¨, 32260 C ¸u ¨nu ¨ r-Isparta, Turkey. E-mail: muhittin@mmf.sdu.edu.tr 2 INCREMENTS Research Group, Institute of Geology and Paleontology, J.W. Goethe University Frankfurt a.M., Senckenber- ganlage 32-34, D-60325 Frankfurt a.M., Germany. E-mail: bioerosion@yahoo.dk FIGURE 1. Locations of studied areas and tectonic features of Turkey (modified from Sintubin and others, 2003; see Fig. 2 for the location names and generalized stratigraphic columns). NAF 5 North Anatolian Fault, EAF 5 East Anatolian Fault. Journal of Foraminiferal Research, v. 36, no. 2, p. 152–165, April 2006 152