The Dam Formation in Qatar is a series consisting of calcareous (calcite, dolomite) and evaporitic sediments (gypsum, celestite) that developed under subtidal through supratidal conditions passing towards younger and older series in an environment of deposition more akin to modern beach deposits. In the present study 87Sr/86Sr ratios, δ44/40Ca and δ44/42Ca data are discussed together with δ13C and δ18O values obtained during an environmental analysis carried out previously. Rather uniform isotope curves of the Sr, Ca and O isotopes for tidal deposits are replaced by more oscillating ones when these tidal-influenced regimes became substituted for by a more wave-dominated regime. Calcium isotope ratios still at its infancy and not fully understood seem to provide a new tool in carbonate petrography when it comes to an interpretation of the environment of deposition and calcification of dolomitic series. The Sr isotopes not only indicate an influx of more primitive Sr from the hinterland but also allow for a refinement of the stratigraphy, which yields a late Aquitanian to early Burdigalian age of sedimentation for the Dam Formation in Qatar.
Holocene carbonate and evaporite sequences in the Arabian Gulf, located mainly along the coasts of the United Arab Emirates (UAE) and Kuwait, have been studied by sedimentologists and ecologists alike (e.g. Shinn, 1983; Sheppard et al., 1992; Saleh et al., 1999; Alsharhan and Kendall, 2002, and references cited therein). In contrast, the sabkhas of the Qatar Peninsula have not been as extensively investigated (Figure 1a). The Qatar Peninsula is the surface expression of the Qatar Arch, a deep structural trend that projects northwards from the Arabian Peninsula into the Arabian Gulf (Cavelier, 1970; Figure 1a). It is covered mainly by Quaternary sandy dunes, aeolianites and calcareous coastal sediments that rest upon Miocene and Eocene calcareous and evaporitic rocks. Despite the great number of outcrops, the investigation of Qatar’s geology is primarily limited to biostratigraphic studies of the calcareous Cenozoic sediments (El Beialy and Al-Hitmi, 1994; Al-Hinai et al., 1997; Al-Saad and Ibrahim, 2002).
In southwest Qatar, the prominent Dukhan Anticline hosts the NNW-trending onshore Dukhan giant oilfield (Sugden, 1962; Foster and Beaumont, 1991; Dill et al., 2003, 2005) (Figure 1b). It presents an excellent locality to study, not only Holocene sabkha sequences, but also the Neogene offshore and continental sediments. Accordingly a research project was conducted to study the sedimentary petrography, mineralogy and chemistry of these sediments. Supplementary palaeontological data were obtained by the study of body and ichnofossils (Dill et al., 2005).
Based upon the palaeontological and sedimentological data, a palaeoecological-palaeoenvironmental analysis of the evaporite-bearing series was successfully concluded (Dill et al., 2005); however the biostratigraphic age of the sediments was not possible. In places, the diversity of species of the macrofossil assemblages is low while the number of individuals is considerably high. This pattern implies a strong environmental stress, and in many beds fossils are absent due to the inhospitable conditions. To circumvent these palaeontological limitations, 87Sr/86Sr ratios of the marine sedimentary rocks were determined and compared with the sea-water ratios (De La Rocha and DePaolo, 2000). Trends of Sr-isotope ratios measured in marine series may be used to both constrain geochronological estimates and to refine the interpretation of palaeohydrological conditions in nearshore environments.
In this paper we present plots of the Sr isotopes together with oxygen, carbon and sulphur isotopes as a function of depth and environment. Also for the first time for these Arabian Gulf Cenozoic rocks, 44Ca/40Ca and 44Ca/42Ca isotope ratios have been determined (see DePaolo, 2004; and Fantle and DePaolo, 2005, for overview of the geological application of Ca-isotope methods). These ratios may assist sedimentologists during environmental analysis. To evaluate the strengths and weaknesses of these methods, the Ca-isotope ratios are discussed in relation to the classical methods of environmental analysis.
Twenty samples were investigated for their Sr and Ca isotope compositions and their Sr concentrations. Sr and Ca isotope analyses were performed at the Federal Institute for Geosciences and Natural Resources, Hannover (BGR). Approximately 50 mg of the sample powders were weighed into Teflon beakers and dissolved in 5 ml ~1.6 M distilled acetic acid at temperatures of 100–140°C on a hot plate for about 32 hours. This procedure was applied in order to dissolve the carbonates but avoid leaching of silicates in the residue. The leachate was separated and recovered from the sample solutions during several steps of centrifuging and washing with ultra-pure water. Different aliquots of the leachate were spiked for determination of Sr concentration using a single Sr spike on the one hand, and for Ca-isotope determination using a double spike enriched in 43Ca and 48Ca, on the other. The leachates were dried and then converted to chlorides. Sr and Ca fractions for mass spectrometrical isotope determination were obtained by standard cation-exchange techniques. An international seawater salinity standard (IAPSO) used as a Sr- and Ca-isotope reference material was treated in a similar manner.
Sr (approximately 200 ng) and Ca (approximately 4 μg) were loaded on Re filaments and run on a double-filament assembly using a Thermo Triton multicollector mass spectrometre in static (Sr) and dynamic (Ca) modes. During Ca-isotope measurement, 40K interference at 40Ca were monitored via 41K but was generally found to be negligible. All Ca samples were measured in replicate (n = 2, 3), the mean of which are reported here. Sr-isotopic ratios were normalised to 86Sr/88Sr = 0.1194. In the course of this study, repeated measurements of the NIST 987 Sr-isotope standard yielded a mean value for 87Sr/86Sr of 0.710248 ± 16 (2 SD). For IAPSO we obtained a Sr concentration of 7.66 ± 0.02 (2 SD) ppm and a 87Sr/86Sr = 0.709181 ± 8 (2 SD; n = 3). The latter value corresponds within error limit to a 87Sr/86Sr ratio of 0.709175 for modern sea water (e.g. Howarth and McArthur, 1997). Because of the young age of the investigated sediments and their very low Rb/Sr ratio as indicated by XRF analysis (Dill et al., 2005), no age correction of the 87Sr/86Sr ratio for decay of 87Rb was applied. Ca-isotope ratios were calculated from mass spectrometric raw data according to the procedure described by Heuser et al. (2002) and are reported in the common delta notation:
in per mil and as the difference to the respective values determined for the NIST SRM915a clinical carbonate standard at the BGR (δ44/40CaNIST915a and δ 44/42CaNIST915a) (Coplen et al., 2002; Hippler et al., 2003). In the course of this study, we obtained δ44/40CaNIST915a and δ44/42CaNIST915a values of 1.88 ± 0.20‰ and 0.89 ± 0.09‰ (2 SD; n = 6), respectively for IAPSO, which agree within error to values determined for this material at other laboratories (e.g. Hippler et al., 2003; Schmitt et al., 2003a). Procedural blanks for Sr and Ca are less than 0.1% of the relevant sample concentration and are therefore negligible. Uncertainties are reported as 2 sigma standard deviation (2 SD) and are 25 ppm for 87Sr/86Sr. Although replicate Ca measurements of samples yielded in part uncertainties that are < = 0.10‰ and < = 0.05‰ for δ44/40Ca and δ44/42Ca, respectively, we assume that the uncertainties quoted above for repeated determinations of homogenous reference materials are more representative of the overall errors in Ca isotope determination. In all calculations, the IUGS-recommended constants (Steiger and Jäger, 1977) were used. The analytical results are presented in Table 1.
LITHOFACIES AND DEPOSITIONAL ENVIRONMENT OF THE MIOCENE DAM FORMATION IN QATAR
The Neogene Dam Formation was subdivided by Dill et al. (2005) into seven members named after type localities on the Qatar Peninsula (Figure 2). In the following paragraphs an overview of the environment of deposition is given based on Dill et al. (2005).
The Lower Salwa Member is a silicate-dolomite-calcite sequence. Fine-grained siliciclastics at the base indicate a deeper marine environment. Calcitic clay-rich marlstone, forming the top stratum indicate an intertidal to beach environment. Bright grey tints among the rock colours are unambiguous redox indicators for well-oxygenated conditions. Trace fossils are ubiquitous in the Lower Salwa Member; their very complex surface tracks and trails belong to the Cruziana Facies of Seilacher (1967). The ichnofossils are Planolites sp. and Thalassinoides sp., both of which are observed on bedding planes of sedimentary rocks that formed in a subtidal environment between 10–100 m water depths.
Part of the Middle Salwa Member has also been interpreted as a restricted platform sedimentary unit. The top strata, however, are interpreted as a beachrock (intertidal environment) very much like the lithologies in the Lower Salwa Member. Red and green rock colours observed in this member indicate varying oxidising and reducing conditions. The basin began deepening during the passage into the Middle Salwa Member. The state of oxygenation deteriorated (dysaerobic reducing conditions), so that part of the environment is described as lagoonal. The water depth in the basin reached a maximum at c. 20 m. In the shallow-marine basin-and-swell topography of the Middle Salwa Member a shift from a microtidal to a mesotidal regime occurred. The basin received a strong terrigenous input from the northwest to north during the deposition of the Middle Salwa Member.
The Upper Salwa Member consists of two coarsening- or shallowing-upward sequences. Trace fossils reappear in the Upper Salwa Member with a burrow morphology most likely attributed to the ichnofossil assemblages of the Callianassa Facies sensuMiller and Curran (2001). The fauna had their habitat in the subtidal to lower intertidal or shoreface environments.
The Lower Al Nakhsh Member encompasses three fully-developed coarsening- or shallowing-upward sequences, each starting with bioclastic calcareous rocks and ending up with stromatolites. Locally, the calcareous sediments are intercalated with some gypsum lenses, or peppered with gypsum concretions. Similar cyclic entities were denominated by Pratt (2002) as peritidal cycles. Tidal channels are indicated in the sedimentary record by the bioclastic pure limestones in the lower section of each cycle (subtidal).
Most cycles encountered in the evaporite-bearing facies of the Middle Al Nakhsh Member are topped by a seam of gypsum. Fully developed cycles may be denominated as brining-upward cycles reflecting a shallowing-upward trend in a supratidal-dominated regime sensuWarren (1999).
The red bed facies in the Upper Al Nakhsh Members with gypsum-bearing coarsening-upward cycle represents the maximum regression following the supratidal regime of the Middle Al Nakhsh Member. It is the most landward (inland sabkha) equivalent of the Middle Al Nakhsh Member. It passes into mottled argillaceous calcrete, which evolved on top of shoals in the sabkha or may grade into arenaceous aeolian deposits.
The calcarenites of the Abu Samrah Member were deposited in a high-energy near-shore marine environment with its flow strength increasing towards younger series as shown, for example, from the eastern coastal plains of the USA (Katuna et al., 1997). The onset of the Abu Samrah Member, marked by a hardground, is equivalent to a transgressive plane. Tidal flats or mudflats evolved in a microtidal regime. In the Abu Samrah Member the marine setting eventually turned from a tide-dominated into a wave-dominated beach environment. A change from wave-dominated to tide-dominated coastal sediments has been reported from environments in the Arabian Gulf in Abu Dhabi (Kirkham, 1998) and the Kuwait-Saudi Arabian Coast (Lomando, 1999). All carbonate and siliciclastic sediments younger than the Middle Salwa were subjected to strong dolomitisation, excluding the uppermost part of the Abu Samrah Member. The calcareous beds immediately beneath the unconformity, which is overlain by fluvial gravely sediments of the Pliocene Hofuf Formation, were named beach rocks.
STRONTIUM ISOTOPES AND THE AGE OF THE FORMATION
The 87Sr/86Sr isotope ratio of the samples varies only within a narrow range from approximately 0.70822 for sample 89 from the base of the section, to maximum values of approximately 0.70850–70854 for samples in the upper part of the section between about 60–70 m above sea level (Figures 3 and 4, Table 1). There is an almost steady increase in the Sr-isotope ratio from the base to the top of the section with only a few outliers at approximately 20 m, 57 m above sea level and within 80–85 m asl (see below) (Figure 4). With respect to the assumed Miocene stratigraphic age of the sediments the Sr-isotopic data fit to the marine Sr-isotope curve for the time interval of approximately 22–18 Ma (Howarth and McArthur, 1997). In Figure 3 the marine Sr-isotope curve for that time interval is eye-fitted (dashed line) to the Sr-isotope data of the section using samples 84.6, 84, 80, 73 and 63 from the lower part, and samples 40, 36, 28, 24 and 21 from the upper part as reference points.
It is evident that most samples fit the marine Sr isotopes in that time interval and thus suggest a late Aquitanian to early Burdigalian stratigraphic age for the section. It is also clear that there are some outliers along the curve: samples from the lowest part (< = 25 m above sea level; Lower Salwa), from approximately 54 m asl (Lower Al Nakhsh) and from the uppermost part (80–85 m asl; Abu Samrah) have significantly lower Sr-isotopic ratios compared to the respective parts of the marine Sr-isotope curve (Figure 3). We interpret these outliers to be due to a significant amount of strontium of non-marine origin in the sample. The lower Sr-isotope ratios may indicate an influx of more primitive Sr from the hinterland. Interestingly, the outliers in the Sr-isotope pattern apparently match outliers to more negative values in the δ13C and δ18O curves along the section signalling an impact of meteoric fluids on the calcareous rocks (Dill et al., 2005) (Figure 4).
CALCIUM ISOTOPES AND THE ENVIRONMENT OF DEPOSITION
The Ca-isotope composition of the samples is relatively uniform with mean δ44/40CaNIST915a and δ44/42CaNIST915a values of 0.85 ± 0.20‰ and 0.41 ± 0.10‰, respectively (Figure 5). Compared to the statistical uncertainties obtained for the homogeneous NIST915a and IAPSO reference materials (0.20‰ and 0.09‰, respectively) the Ca-isotope data of the samples indicate that there are no significant Ca-isotope variations throughout the sampled section. Furthermore, the Ca-isotope ratios do not show an overall increase or decrease from the base to the top of the section. Nevertheless, there are some obvious disturbances in both Ca-isotope curves, which in part match those of the other isotope curves (87Sr/86Sr, δ13C and δ18O): at the base of the section, between 50 m and 55 m and in the uppermost part of the section. In these sections, the Ca-isotope budget may be influenced by a contribution from other non-marine sources. Judging from the similarity of the δ44/40CaNIST915a and δ44/42CaNIST 915a curves of the samples, no significant contribution of more radiogenic 40Ca coming from old continental sources is evident for those parts of the section for which a supratidal or freshwater environment may be invoked (see supratidal subenvironments) (Figure 4).
Calcareous sediments of marine origin generally show negative δ44/40Ca and δ44/42Ca values relative to seawater of appropriate age (see Fantle and DePaolo, 2005; Heuser et al., 2005; DePaolo, 2004 for compilation of earlier studies). Thus, they are enriched in the lighter (40Ca, 42Ca) over the heavier Ca isotopes (for instance 44Ca) relative to seawater due to mass-fractionation processes during their formation. The exact nature, extent and controls of these fractionation processes are still not well understood. It is assumed that calcareous sediments of chemical origin show slightly different fractionation behaviour as compared to carbonates formed by biomineralisation (Schmitt et al., 2003a). In addition, δ44/40Ca and δ44/42Ca values of chemically formed carbonates and phosphorites of identical stratigraphic age may vary due to mineral-dependant kinetic mass-fractionation (Gussone et al., 2003; Schmitt et al., 2003b). The Ca-isotope composition of palaeo-seawater itself is a function of the complex evolution of its Ca-elemental budget in the past (Fantle and DePaolo, 2005; Heuser et al., 2005; DePaolo, 2004 for overview of earlier studies).
For the early Miocene, models suggest a significant decrease in the δ44/40CaNIST915a value of seawater from approximately +2.0‰ (22 Ma) to +1.4‰ (18 Ma) (De La Rocha and DePaolo, 2000; Schmitt et al., 2003a; Schmitt et al., 2003b; DePaolo, 2004; Heuser et al., 2005). Ca dissolved in modern river waters is isotopically lighter in δ44/40Ca by about 0.7–1.7‰ compared to modern seawater (Zhu and MacDougall, 1998; Schmitt et al., 2003a; DePaolo, 2004). The lowest δ44/40Ca values of -1.4 to -1.7‰ (relative to seawater) are reported for Ganges tributaries, which also show high 87Sr/86Sr ratios. This suggests that their low δ44/40Ca values may in part be due to excess 40Ca accumulated from radioactive decay of 40K in chemically strongly fractionated igneous rocks in the hinterland. Analyses of rainwater and groundwater also reveal δ44/40Ca values that are by 0.9–1.5‰ lower compared to modern seawater (Schmitt et al., 2003a).
Marine carbonates are isotopically lighter than seawater by about 1.3‰ (biogenic carbonates) to 1‰ (phosphorites) (De La Rocha and DePaolo, 2000; Schmitt et al., 2003b; DePaolo, 2004). Therefore, for early Miocene carbonates formed in a marine environment δ44/40CaNIST915a values of approximately 1.0–0.1‰ are expected. The investigated samples for which Sr isotope data give evidence of a formation age of 22–18 Ma before present show δ44/40CaNIST915a values of on average 0.85 ± 0.20‰. The Ca-isotope data are therefore in line with a formation of the sediments in a marine environment without significant contributions from other sources to their calcium budget.
EARLY MIOCENE SERIES ALONG THE NORTHEASTERN MARGIN OF THE ARABIAN PLATFORM
The section through the southern part of the Dukhan Anticline (Dill et al., 2005) takes the centre-stage for the correlation of early Miocene sedimentary sequences along the north-eastern margin of the Arabian Platform. It is correlated to reference sections in Dhofar, Oman (Roger et al., 1987); the western regions of the United Arab Emirates (Ditchfield et al., 1999; Whybrow et al., 1999); the Dammam region, Saudi-Arabia (Weijermars, 1999); and south-western Iran (Motiei, 1993) (Figure 6). Cavalier (1970) suspected a middle to late Miocene age for the Dam Formation in Qatar. A late Aquitanian to early Burdigalian age of sedimentation may be concluded from the Sr isotopes presented in this paper. Hence, early Miocene sedimentary sequences along a SE-NW section can be correlated and treated in more detail as to their lithology, environment of deposition and their sequence stratigraphic key elements (Figure 6).
In Dhofar, Oman, the Mughsayl Formation represents the early Miocene (Roger et al., 1987). The onset of turbiditic calcareous rocks was dated as early as late Stampian (early Oligocene) and lasted until the middle Burdigalian when conglomeratic limestones of the Adawnib Formation came to rest unconformably on top of the Mughsayl Formation. The slumped calcareous sediments of the Mughsayl Formation were laid down in a pelagic environment of deposition, whereas the hangingwall rocks of the Adawnib Formation were apparently deposited in a marginal marine environment.
In the UAE, only the upper part of the Dam Formation is exposed and it consists of dolomitic claystones and hardgrounds. The strontium-isotope record published by Peebles (1999) for Abu Dhabi suggests a Burdigalian age. During the Neogene mainly clastic series formed. They were defined as the Shuwaihat Formation (lower part) and Baynunah Formation (upper part). Whybrow et al. (1999) found an erosional surface in the Shuwaihat Formation with a relief of at least 6 m that was subsequently covered by the overlying sediments. Aeolian cross-stratification are distinctive features of the Shuwaihat Formation, which is apparently coeval with the Hofuf Formation that unconformably overlies the Dam Formation in Qatar and Saudi Arabia (Figures 4 and 6). Due to the lack of faunal or floral remains this siliciclastic sequence can only be assigned a middle Miocene to Pliocene age. Aeolian sediments recorded from Abu Dhabi have also been encountered in the section of the southern Dukhan Anticline (Figures 4 and 7). In addition to these continental sediments, pedological and hydrological processes in the reaches of a fluctuating ground-water level gave rise to argillaceous dolomitic calcretes (“dolcretes”) (Figure 8). Dissolution of highly soluble compounds (halite?) in the subsurface has given rise to dolines and caused a pervasive karstification at this site (Figure 9). A relative increase in relief on a rather small scale resulted from differential salt dissolution at depth and halokinetic processes along the northeast limb of the Dukhan Anticline. The uppermost part of the Dam Formation in Qatar (Upper Al Nakhsh and Abu Samrah Members) could not be chronologically constrained by means of Sr isotopes and, hence, its age remains conjectural. Aeolian sediments, duricrust and prominent karst relief in the Qatari reference section suggest that the uppermost Dam Formation correlates to the lowermost Shuwaihat Formation in the UAE, where Whybrow et al. (1999) described significant erosional features.
In Saudi Arabia, the Dam Formation is said to be middle Miocene in age (Powers, 1968; Weijermars, 1999). In the type section it overlies the Hadroukh Formation while in the Dammam region, it unconformably overlies the Ypresian-Lutetian Dammam or Ypresian Rus formations. The Hadroukh Formation is considered by Weijermars (1999) as Aquitanian to Burdigalian (23.7–20 Ma) in age. This means that the lower Dam Formation in Qatar, which is rife with fine-grained siliciclastic rocks, is coeval with the uppermost Hadroukh Formation on the Dammam Peninsula in Saudi Arabia.
The Dam Formation is stratigraphically equivalent to the Middle Asmari Formation in Iran (Motiei, 1993, inSharland et al., 2001). According to these authors, the Middle Asmari Formation consists in the lower half of siliciclastics and carbonates and in the upper half of dolomites and carbonates. The dolomitic section is correlative with evaporitic series in the Lower and Middle Al Nakhsh members in Qatar.
The sedimentary sequence taken for reference in Oman marks the transition from deep towards shallow marine. Stratigraphically equivalent series from Saudi Arabia, Qatar and the western UAE are typical of shallow marine and strongly influenced by the uplift of the Qatar Arch (Figures 1, 4 and 6). Erosional surfaces or discontinuities of local scale may be due to differential uplifts over the various salt-cored anticlines (e.g. Dukhan Anticline, Dammam Dome) in this part of the Arabian Platform. The drill section in Ab-Teymur-1 in Iran (Motiei, 1993) represents a deeper part on the northern shelf of the Arabian Platform.
The most pronounced sequence boundary to be traced on a regional scale separates the shallow-marine carbonate sequences of early Miocene age (Dam Formation) from the siliciclastic series of the Hofuf Formation and lithological equivalent series found at outcrop in the UAE. The maximum flooding surface MFS Ng10 sensuSharland et al. (2001) cannot be identified in all the studied reference sections. According to the present study, this MFS has to be drawn within the siliclastic-dominated Middle Asmari Formation in Iran, the marly Lower Dam Formation (Middle Salwa Member) in Qatar and in the calcareous Mughsayl Formation in Oman. If MFS Ng20 exists at all in the Dam Formation of Qatar, it has to be “squeezed” between the sequence boundary truncating the Dam Formation and the “intra-Dam erosional surfaces” (Figure 4). In both cases, the MFS Ng 10 and Ng 20 coincide with a “relative low” in the chemologs, illustrating the distribution of isotope ratios (Figure 4).
Calcareous and evaporitic sediments (gypsum, celestite) of the Dam Formation in Qatar reflect deposition under subtidal through supratidal conditions, which towards the base and the top of the series are replaced by an environment of deposition more akin to a modern beach. A rather uniform isotope curve of Sr, Ca and O isotopes for the tidal deposits is replaced by a more oscillating one when these tidal-influenced regimes became substituted for by a more wave-dominated regime. Small-scale disturbances of the isotope ratios in the Lower Al Nakhsh Member are correlative with the onset of the evaporite series in the section under study. The Sr isotopes do not only indicate an influx of more primitive Sr from the hinterland, but also allow for a refinement of the stratigraphy, which yields a late Aquitanian to early Burdigalian age of sedimentation for the Dam Formation in Qatar. Calcium isotope ratio studies, still in their infancy and not fully understood, seem to provide a new tool in carbonate petrography when interpreting the environment of deposition and calcification of dolomitic series. The isotope ratios need to be tested to determine if they can assist in positioning the planar architectural elements of sequence stratigraphy. The present study is promising in that way but not yet a proof, and needs further geochemical support.
The first author is grateful for the support provided by the Scientific and Applied Research Centre (SARC), which provided transportation in the field and to S. Nasir (Sultan Qaboos University, Muscat, Oman) and H. Al-Saad (University of Qatar). We acknowledge the laboratory support by S. Gerlach and P. Macaj (both BGR). We thank two anonymous reviewers for their important suggestions that have improved the manuscript. The final design and drafting by Nestor Niño Buhay is appreciated.
ABOUT THE AUTHORS
Harald G. Dill is involved in international technical training with the German Federal Institute for Geosciences and Natural Resources (BGR) and is an Associate Professor at Hannover University. He studied Geology and Mineralogy at Würzburg, Aachen, and Erlangen universities and received a Diploma in Geology in 1975 and a Doctorate in Mineralogy in 1978. Harald conducted research at Bayreuth University before joining BGR in 1979. In 1982, he became Lecturer in Applied Geology at Mainz University where he was awarded his Doctor Rerum Naturalium Habilitatus in 1985. From 1986 to 1991, he was assigned to the Continental Deep Drilling Program of the Federal Republic of Germany. In 1991, Harald was appointed Associate Professor in Economic Geology at Hannover University. In the same year he rejoined BGR in the Department of Economic Geology and International Cooperation training geologists in sedimentology and the geology of non-metallic mineral deposits through international cooperation schemes. Harold lectures in Economic Geology and Sedimentology at Hannover University, elsewhere in Germany, and abroad. He has published over 200 papers and abstracts on the sedimentology and economic geology of metallic and non-metallic deposits in South America, Asia, and Central Europe. His interest lies in the capture of digital data in the field and the study of heavy minerals as well as mineral and energy deposits, mainly within sedimentary rocks.
Friedhelm Henjes-Kunst is a Research Scientist at the Department of Geochemistry and Mineralogy of the German Federal Institute for Geosciences and Natural Resources (BGR), specializing in isotope geochemistry and geochronology of igneous, metamorphic and sedimentary rocks. He studied mineralogy at the universities of Clausthal-Zellerfeld and Braunschweig and received a Diploma in 1976 and a Doctorate in 1980 both in Mineralogy. Afterwards, Friedhelm was involved in research projects at the universities of Münster, Karlsruhe and Freiburg covering petrology, geochemistry and isotope geochemistry of granitoids, rift-related volcanics and mantle-derived rocks. In 1990, he joined the BGR in the isotope geochemistry section. Since then, his major research interests were assigned to the Continental Deep Drilling Program of the Federal Republic of Germany and to the Polar Geoscience Program of the BGR. Friedhelm joined six expeditions to Antarctica and one to the Canadian High-Arctic. Since 2001 he has been involved in the investigation of ore deposits. His major interests are application of unconventional isotope methods to investigate formation and age of ore deposits.