doi: 10.1111/ter.12058 The rise of the diptera-microbial mat interactions during the Cenozoic: consequences for the sedimentary record of saline lakes M. Esther Sanz-Montero,1 Jose-Pedro Calvo,1 M. Angeles Garcıa del Cura,2 Concepcion Ornosa,3 Raimundo Outerelo3 and J. Pablo Rodrıguez-Aranda1 1Departamento de Petrologıa y Geoquımica, Facultad de Geologıa (UCM), C/Jose Antonio Novais, 2, Madrid 28040, Spain; 2Instituto de Geociencias (CSIC-UCM), C/Jose Antonio Novais, 2, Madrid 28040, Spain; 3Departamento de Zoologıa y Antropologıa Fısica, Facultad de Biologıa (UCM), C/Jose Antonio Novais, 2, Madrid 28040, Spain ABSTRACT Shoreline gypsiferous sediments of an inland lake in central dae hinders significant preservation of microbialites. The Spain furnishes valuable insight into reconstructions of early overwhelming rise of Diptera at the onset of the Cenozoic sedimentary changes related to shore fly–microbial mat inter- resulted in extensive feeding and dwelling activity and con- actions in fossil gypsum precipitating saline lake systems. The tributed to reshape the saline aquatic habitat where microbial association of adult and larval forms of Ephydra (Diptera) mats thrived, thus leading to the formation of specific trace with microbial matgrounds overlying the lake margin results fossils that are illustrative of the existence of microbes in the in the formation of gypsiferous meniscate back-filled burrows paleoenvironment. that provide an analogue for recurring, extensively developed trace fossils that occur in Cenozoic, but not older, lacustrine Terra Nova, 25, 465–471, 2013 gypsum rocks. In this setting, sediment burrowing by ephydri- that the presence of shallow feeding living in arid zone shallow ephemeral Introduction burrows associated with matgrounds waters with drastic seasonal salinity Although the concept of Phanerozoic has recurred at certain times in fluctuations (Krivosheina, 1986). stromatolite decline by grazing and Earth’s history. Under these extreme conditions, burrowing animals (Garrett,1970; Some invertebrates feed and grow shore flies and their cyanobacteria Awramik, 1971) was considered too well on cyanobacterial substrates food are often the only successful simplistic (Pratt, 1982), it is generally (Monakov, 2011). However, most organisms. Ephydridae not only toler- accepted that the appearance of examples of successful exploitation of ate high salinities, with their optimal three-dimensional trace fossils in cyanobacteria under natural condi- range around 180& (Warren, 2006, Early Cambrian strata testified to a tions come from dipteran larvae (Fo- p. 637), but require certain concentra- behavioural revolution (Seilacher, ote, 1977). Laboratory experiments tions for survival and normal devel- 1999). The rapid evolution of effi- conducted by Krivosheina (2008) con- opment (Herbst, 1999). cient grazing animals constrained firmed the ability of higher Diptera, The appearance of higher Diptera development of benthic mats while dominantly Ephydridae, to feed on took place in the Late Cretaceous bioturbation disrupted buried mats and digest cyanobacteria. Ephydri- (Blagoderov et al., 2002). Through- and closed a taphonomic window of dae, also called shore flies, alkaline or out the Palaeogene, the dominant preservation for soft-bodied organ- brine flies (Foote, 1995), are common structure of Diptera gradually shifted isms (Gehling, 1999). The earliest in aquatic habitats throughout the to the modern one. By the beginning mobile animals are interpreted to world and they often are the sole of the Neogene, dipteran ecological have burrowed microbially bound insect species of the benthic and and taxonomic diversity expanded sediments for food resources (Geh- shoreline portions of inland saline rapidly, which resulted in the appear- ling, 1999; Gingras et al., 2011). This lakes and ponds (Herbst, 1988). ance of the polydominant fauna of interaction was conducive to a Ephydridae are an important food modern type. The ancestors of mod- remarkable increase in the degree of source for wildlife in saltwater pools, ern higher Diptera were adapted for bioturbation of the sediment. Buatois such as it is observed in Mono Lake, life as saprophages in rotting vegeta- and Mangano (2011) have noticed California, where millions of birds are tion (Ferrar, 1987). The adaptative supported almost entirely by ephydr- radiation of higher Diptera, for Correspondence: Dr. M. Esther Sanz- ids (Jehl, 1986; Rubega and Inouye, instance Ephydridae, to different spa- Montero, PhD, Petrologıa y Geoquımica, 1994). Other insects, such as dragon- tial and trophic resources like micro- Facultad de Ciencias Geologicas, Univers- flies and chironomids are also com- bial mats, illustrates some reasons idad Complutense, C/ Jose Antonio Nov- mon inhabitants of modern and for the ample widespread success of ais, 2, Madrid 28040, Spain. Tel.: ancient saline lake environments this type of insects in wetlands (Kei- +34 91 394 49 18; fax: +34 91 544 (Brennan and McLachlan, 1979; per et al., 2002). 25 35; e-mail: [email protected], Gingras et al., 2007; Scott et al., Preservation of organic remains [email protected] 2009). Ephydridae are well adapted to and/or ichnofabrics in sedimentary © 2013 John Wiley & Sons Ltd 465 The Cenozoic rise of the diptera-microbial mat interactions • M. E. Sanz-Montero et al. Terra Nova, Vol 25, No. 6, 465–471 ............................................................................................................................................................. deposits that accumulated in saline ally, the burrow traces form a very sil saline lake systems. As discussed environments is usually poor (War- dense network within the sediment below, these processes were especially ren, 2006), which makes paleoecolog- and locally exceed 60% of the total significant after the end of the Creta- ical reconstructions more challenging volume of the gypsum strata ceous. (Truc, 1980; Palacios-Fest et al., (Figs 1A and B). The individual bur- 1994). In contrast, strongly burrowed rows are 0.5–5 mm in diameter, and Methods gypsum deposits showing a tangle- up to 5 cm in length (Fig. 1B) within pattern structure occur in several the tangle-pattern fabric. The bur- Fieldwork in Lake El Longar (altitude fossil evaporite lake basins in the rows display typical meniscate infill 683 m amsl) (Fig. 2) was conducted Cenozoic record, especially from the composed of lenticular gypsum, fae- in five campaigns during different sea- Mediterranean region (Truc, 1980; cal pellets and variable amount of sons between 2009 and 2012. Sedi- Ortı and Salvany, 1990; Arribas micrite and/or clay (Figs 1C and D). mentological work and sampling were et al., 1991; Rodrıguez-Aranda and The gypsum meniscate infill appears mainly performed along the eastern Calvo, 1998; Huerta et al., 2010; Dr. to have further aided in their recog- marshy shoreline (Fig. 2). The Ibrahim Gundogan,€ 2012, pers. nition. exposed shoreline varies over the sea- commun.). In the basins, up to 150- This article focuses on microbial sons and it may reach some tens of m-thick sedimentary sequences mats thriving in the inland saline metres in the dry periods. containing burrowed gypsum beds Lake El Longar, central Spain, that Water temperature, salinity and were deposited in shallow, but exten- offers a chance to compare extant lit- pH immediate measurements were sive lakes that covered areas of hun- toral biomats burrowed by Ephydri- taken with a PC300XS Sampler. dreds to thousands of km2. Burrows dae with Cenozoic bioturbated Water samples were collected in occur throughout gypsum beds that gypsum deposits. Thus, this study duplicate directly from the lake. The locally reach up to 1 m in thickness provides for the first time a modern water anions were determined by and show a diffuse, mottled structure analogue for interpreting gypsiferous electrophoresis, the cations by atomic (Fig. 1A). Selective silicification meniscate back-filled burrows. More- absorption and carbonates and bicar- enhancing morphological traces of over, observation from this modern bonates by titration in the Geochem- the burrows is locally recognized environment furnishes valuable istry Laboratory of the Museo (Fig. 1B) (Arribas et al., 1991; Sanz- insight into reconstructions of early Nacional de Ciencias Naturales- Montero et al., 2008; Sanz-Montero sedimentary changes related to shore CSIC (Madrid). and Rodrıguez-Aranda, 2009). Usu- fly–microbial mat interactions in fos- Diptera specimens were studied and images taken using a stereo- scopic binocular microscope. (A) (B) Forty organosedimentary samples comprising mineral and microbial mats were collected by hand and by using a PVC dredging device dug up to 10 cm deep into the shoreline matground. The mineralogy was determined by XRD of powdered specimens on a Philips X-ray diffrac- tion system. For preparation of thin- sections, sediment samples were dehydrated by lyophilization, embed- (D) (C) ded and impregnated with Epofix resin. Optical and fluorescence SPAIN Madrid Lillo 250 km Fig. 1 Examples of bioturbated gypsum from the Miocene of the Madrid Basin. Rocks shown in A and D crop out in the vicinity of Lake El Longar, their location ° ′ is arrowed in Fig. 2. B and C bioturbated rocks crop out at Brea de Tajo (40 14 1 km 15″ N, 3°4′32″ W; altitude 725 m amsl) (Rodrıguez-Aranda, 1995). (A) Close-up view of a burrowed gypsum bed characterized by a diffuse, mottled appearance, pen cap for scale = 40 mm long. (B) Hand sample showing silicified gypsum bur- Fig. 2 Location map and satellite