Abstracts with Programs - Geological Society of America

in both cratons probably reflects the breakup of the supercontinent Rodinia and therefore
the same tectono-magmatic event. Our results indicate a similar history for India and South
China which both underwent at least one synchronous episode of crustal growth during the
Neoproterozoic. In addition, our data set shows that both passive margin clastic sequences
had the same source area for all zircons older than Neoproterozoic. Therefore we infer that
India and South China were close to each other and along the same passive margin during
the breakup of Rodinia in the Late Neoproterozoic.
6-2 11:20 Han, Guoqing
LA-ICP-MS U-PB DATING AND HF ISOTOPIC COMPOSITIONS OF DETRITAL ZIRCONS
FROM THE “PERMIAN” SANDSTONES IN DA HINGGAN MOUNTAINS, NE CHINA:
CONSTRAINTS ON THE EVOLUTION OF THE EASTERN SEGMENT OF CENTRAL
ASIAN OROGENIC BELT
HAN, Guoqing1 , NEUBAUER, Franz1 , LIU, Yongjiang2 , ZHANG, Xingzhou2 , JIN, Wei2 ,
GENSER, Johann1 , REN, Shoumai3 , and LI, Wei1 , (1) Dept. Geography and Geology,
University of Salzburg, Hellbrunnerstr. 34, Salzburg, A-5020, Austria, guoqing.han@
stud.sbg.ac.at, (2) College of Earth Sciences, Jilin University, Jianshe Str. 2199,
Changchun, 130061, China, (3) Strategic Research Center of Oil & Gas Resources,
MLR, Funei Str. 88, Xicheng District, Beijing, 100034, China
We present new LA-ICP-MS U-Pb age data and Hf isotopic compositions of detrital zircons
from supposed Mid to Upper Permian sandstones from the molasse-type lacustrine-fluviatile
Linxi and Zhesi Fms. of the Da Hinggan Mountains (eastern Inner Mongolia, China). Our new
data constrain the eastern extension of the Erenhot-Hegenshan suture zone and the plate
collision processes between the northern margin of the North China craton and the composite
Erguna-Hinggan-Songliao block. The U-Pb ages of detrital zircons indicate ages as young as
Late Permian to Early Triassic indicating a younger depositional age as previously assumed.
These data also show two uniform age groups of 270–280 Ma and 310–320 Ma, and zircons
of the older cluster are considered to derive from the Sonidzuoqi-Xilinhot magmatic arc with its
age cluster of 310–320 Ma and similar εHf (t) values of 3.46–10.41. The younger, 270–280 Ma
age group is interpreted to derive from a post-orogenic A-type granitoid belt.
Synthesizing this unique information on a magmatic arc of an approximate age of 320 Ma
we define a distribution of the Sonidzuoqi–Xilinhot magmatic arc as follows. The arc extends
from Solon Obo via Sonidzuoqi, Xilinhot through Ulanhot to Qiqihar, and then it is cut by the
sinistral Nenjiang-Balihan slip-strike fault (western boundary fault of the Songliao basin), and
ultimately extends to Longzhen in the northern sectors of the Da Hinggan Mountains. The
Erenhot-Hegenshan suture zone is located north of this magmatic arc. Further Paleozoic age
groups of ~380 Ma, ~430 Ma and ~500 Ma in the samples indicate a mixture of age groups
of variable origin and multiple arc-continent accretion during the formation of the composite
Erguna-Hinggan-Songliao block. The sample from the uppermost Permian to Lower Triassic
Linxi Formation in the Linxi area (in the southern segment of Da Hinggan Mountains) has two
age groups of ~1800 Ma and ~2500 Ma, indicating their source from the northern margin of
the North China craton located in the south. Therefore, the collision between the North China
craton and the Hinggan-Erguna block started during the deposition of the Linxi Formation and
the final closure of the intervening oceanic basin occurred during Late Permian-Early Triassic
forming the Ondor Sum-Xar Moron suture zone.
6-3 11:35 Kirscher, Uwe
CONSTRAINTS ON THE TECTONIC EVOLUTION OF THE SOUTHERN SEGMENT OF THE
CENTRAL ASIAN OROGENIC BELT BY PALEOMAGNETIC DATA
KIRSCHER, Uwe1 , MIKOLAICHUK, Alexander2 , ALEXEIEV, Dmitry V. 3 , and
BACHTADSE, Valerian1 , (1) Earth and Environmental Sciences, Ludwig-Maximilians-
University, Theresienstrasse 41, Munich, 80333, Germany, uwe.kirscher@
geophysik.uni-muenchen.de, (2) Institut of Geology, Kyrgyz Academy of Sciences,
Bishkek, 720027, Kyrgyzstan, (3) Geological Institute RAS, Pyzhevskiy 7, Moscow,
119017, Russia
A detailed paleomagnetic investigation has been carried out on sedimentary and volcanic
rocks of Paleozoic age in the Kyrgyz Tien Shan in order to elucidate the paleotectonic and
paleogeographic parameters for the evolution of the Central Asian Orogenic Belt (CAOB)
during Paleozoic times.
The paleomagnetic data obtained so far generally agree with other published data for coeval
rocks, mainly from Kazakhstan. Combining the different data sets, results in two distinct swaths
for the Ordovician and Carboniferous which are both displaced to the east of the European
Apparent Polar Wander Path (EuAPWP). Whereas the Ordovician mean paleo- south poles are
spread between 20° to 100° E in longitude and 0° to 40° S in latitude, the Carbonifeous pole
positions plot in a region between 320° and 140° E in longitude and 65° to 40° S in latitude.
Both define more or less parallel small circles which pass through the Ordovician and
Carboniferous segments of the EuAPWP, respectively. The poles of rotation for both small
circles plot in today’s Siberia and are only some 15° apart.
We note that the amounts of rotation are not a function of age of individual pole positions
leading to the conclusion that both small circles are the result of individual blocks rotating by
individual amounts with respect to each other and the EuAPWP during post-Carboniferous
times. We furthermore conclude that the pole positions identified in this study display a closer
proximity to the EuAPWP than to the APWP for Siberia.
6-4 11:50 Sonntag, Benita-Lisette
INTRA-CONTINENTAL SHORTENING ALONG THE ALAI VALLEY, PAMIR-TIEN SHAN,
CENTRAL ASIA
SONNTAG, Benita-Lisette, HOFMANN, Jakob, LOHR, Tina, RATSCHBACHER, Lothar,
SCHMALHOLZ, Martina, and JONCKHEERE, Raymond, TU Bergakademie Freiberg,
Institut für Geologie, Freiberg, 09596, Germany, benita-lisette.sonntag@geo.tu-freiberg.de
The Alai Valley between the Pamir frontal range and the southern Tien Shan is the remnant
of a Cenozoic sedimentary basin that linked the Tajik basin to the west and the Tarim basin in
the east. The ‘Main Pamir Thrust’ corresponds to a major thrust splay of the intra-continental
subduction zone along which Asian lithosphere is subducting southward under the Pamir
along a seismically active zone. Late Cenozoic deformation is separated into several segments
and the lateral transitions are accommodated by complex areas of transfer faults and thrust
systems. Map interpretation and evaluation of structural data indicates up to 40° clockwise
rotation of the shortening direction from NNW-SSE to NNE-SSW since the late Miocene.
Distinct differences in the fault pattern between several segments of the northern Pamir and
between the northern Pamir and the southern Tien Shan are effects of local block rotations.
Active deformation of the Pamir frontal range is obvious from Recent surface breaks along the
western and central segments; the disastrous Mw 6.7 Nura earthquake on October 5th , 2008
testifies to renewed activity along the eastern segment. The southern Tien Shan shows active
deformation in the eastern part that interacts with the dextral Talas-Ferghana fault system.
Estimates on the age of deformation are based on the tectonic interpretation of facies
variations in shallow marine and continental sedimentary rocks. Distributed north-south
contraction occurred during the late Oligocene–early Miocene with shortening resumed in the
late Miocene. According to new Ar-Ar geochronology, the southern Tien Shan cooled through
300°C at ~275 Ma, following a major intrusion event at 305-280 Ma (U-Pb zircon), and later
through ~100°C at ~10-15 Ma. Sandstone samples from Paleogene and Miocene strata from a
SESSION NO. 7
intra-montane basin in the southern Tien Shan yielded detrital apatite and zircon fission-track
data with age peaks at ~ 330, 250, 170, 145, and 75 Ma that are not reset during the Cenozoic.
Detrital apatite and zircon from the Pamir frontal range are also unreset, yielding age peaks
at ~240 Ma and ~140 Ma. The only Cenozoic ages from the thrust system of the Pamir frontal
range stem from Lower Cretaceous sedimentary and Paleozoic volcanoclastic rocks and
suggest that the major shortening is ≤5 Ma.
6-5 12:05 Kley, Jonas
SEDIMENTARY AND TECTONIC EVOLUTION OF THE CENOZOIC ILI BASIN (NORTHERN
TIEN SHAN, KAZAKHSTAN)
KLEY, Jonas1 , VOIGT, Thomas1 , SEIB, Nadine1 , and KOBER, Martin2 , (1) Institute of
Geosciences, Friedrich Schiller University, Burgweg 11, Jena, 07749, Germany, Jonas.
Kley@uni-jena.de, (2) Institute of Geosciences, Friedrich Schiller University, Wöllnitzer
Straße 7, Jena, 07745, Germany
The Ili basin is a triangle-shaped Cenozoic broken foreland basin located between the Northern
Tien Shan and Dzungarian Alatau thrust fronts in Kazakhstan. It is disrupted by several thrustrelated
basement uplifts.
The most representative sections occur in the piedmont of the Katutau basement range.
Distal deposits emerge in the Aktau anticline while proximal strata overlie the Paleozoic
basement in the north and west. The Aktau succession whose base is not exposed starts in
the middle Oligocene (mammal fossils; Indricotherium horizon) with fluvial deposits of a large
river system and varying flood-plain deposits exhibiting intense soil formation (calcretes and
gypsisols). Transport directions and quartz content of these sediments suggest they were not
sourced from the nearby mountain ranges present today. They are followed by late Oligocene
to Miocene strata reflecting the transition from an evaporitic lake/playa system to freshwater
lacustrine conditions, eventually grading into a large sandy river system.
In the proximal settings, alluvial and fluvial deposits rest on deeply weathered paleosurfaces.
Transport is mainly to the south. Alluvial fans dominated by tabular conglomerate sheets are
sharply overlain by fine-grained sandy mudstones with frequent calcareous paleosols. These
represent terminal alluvial fan and playa deposits interfingering with freshwater lake deposits,
finally also giving way to sandy fluvial strata reminiscent of the modern Ili river. The basal fluvial
deposits can be confidently correlated from the Aktau to the proximal successions on the
basis of facies and clast spectra. Up section the correlation is not as clear, although the main
lacustrine episodes and the transition to the sandy fluvial system may coincide.
The rapid tapering from the Aktau section into much thinner, more coarse-grained and
more proximal successions may in part reflect restricted sediment transport in a very arid
environment. In addition, it is apparently mediated by NNW-trending normal faults displacing
the Cenozoic strata at least up to the Upper Miocene. Some of these normal faults were
later reactivated as dextral strike-slip faults. The Ili Basin apparently originated as a mildly
extensional basin in Late Paleogene time and evolved into a foreland basin possibly as late
as Pliocene time.
6-6 12:25 Dogra, N.N.
PALYNOCHRONOLOGICAL CONSTRAINTS FROM HIMALAYAN FORELAND BASIN AND
THEIR IMPLICATIONS ON INDIA – ASIA COLLISION
DOGRA, N.N. Sr1 , SINGH, Y.R. 2 , THAKUR, O.P. 1 , and KUMAR, Sandeep1 , (1) Department
of Geology, Kurukshetra University, Haryana, Kurukshetra, 136119, India, nndogra@
rediffmail.com, (2) Department of Earth Sciences, Manipur University, Canchipur, Imphal,
795003, India
India-Asia collision took place 65-40 m.y ago averaging around 55 m.y resulted into the
formation of Himalayan Foreland basin. We document the palynochronological evidence
for initiation of Himalayan Foreland sedimentation in the Proterzoic basement subsidence
developed as a consequence of this collision. Initial Foreland sediments of Himachal
Pradesh designated as Kakara and Subathu formations are investigated in detail for the
plant microbiota to generate a new evidence line of palynochronological inferences for this
continental-continental collision and subsequent evolution of Himalayan Foreland basin. The
plant microbiota recovered here from the Early Tertiary Subathu Formation in the stratotype
point to different ecological settings depicting, marine, marginal marine, coastal transitional
and freshwater depositional episodes in the Subathu Formation based on Homotryblium
(52-51 my), Cordosphaeridium (52-51 my), Cleistosphaeridium (51-44 my) and Pediastrium
(< 44 my) Assemblage zones from Ypresian to post-Lutetion time intervals.
Palynozones dates are designated based on global age marker palynotaxa (Williams et al.
1993). Based on the FAD and LAD limits of taxa recovered in each zone, we here propose
to delimit the precise age of zones by delimiting youngest FAD and oldest LAD of taxa in the
assemblage of a particular zone. The palynochronological dates so delineated in the present
studies clearly point out the deposition of Subathu Formation from 52 to 44 m.y and may be
even younger, for the age diagnostic palynotaxa from the uppermost part of Subathu Formation
represented by Pediastrum Assemblage zone are still wanted. The Kakara Formation of Nahan
area yielded marine Dinogymnium assemblage which is index of Maestrichtian.
The qualitative, quantitative and palynochronological data from Kakara and Subathu
Formation of northwest Himalaya constrain that the north ward movement of Indian plate,
underthrusting of Tethys crust, end Cretaceous cessation of sedimentation in Spiti basin,
closure of Neotethys in the north and the eventual collision of India with Asia coincides with
the initiation of marine sedimentation in Maestrichtian time in the Himalayan Foreland basin
and the evolution of basin is accompanied with deposition of Subathu Formation under shallow
water marine influene from 52 to 44 m.y. ago.
SESSION NO. 7, 08:30
Monday, 5 September 2011
Open Session in Geosciences (Posters)
Ludwig-Maximilians-Universität München,
Poster Hall P3 (1st floor hallway)
7-1 BTH 6 Tarabees, Elhamy
APPLICATION OF THE VELOCITY-DEVIATION LOG IN DETERMINING PORE TYPES AND
PERMEABILITY TRENDS OF NUBIA S.S FORMATION, IN RUDEIS-SIDRI AREA, GULF OF
SUEZ, EGYPT
TARABEES, Elhamy, Geology Department, Faculty of Science, Damanhour University,
Damanhour 22516 Egypt, etarabees@yahoo.com
The velocity-deviation log, which is calculated by combining the sonic log with the neutronporosity
or density logs, provides a tool to obtain down hole information on the predominant
pore types in sandstone rocks. This information can be used to trace the down hole distribution
of diagenetic processes and to estimate the causative trends in permeability. The velocitydeviation
log calculated by converting porosity-log data to a synthetic velocity log using the
Munich, Germany A9
Monday