828 NOTES STRATIGRAPHY OF BARMER BASIN, RAJASTHAN: IMPLICATIONS ON CRETACEOUS-TERTIARY BOUNDARY* M.S. SISODIA Department of Geology, J.N.Vyas University, Jodhpur - 342 005 Email: [email protected] EXTENDED ABSTRACT Earth scientistshave been in pursuit for 'longto frnd the anoma\iesmd as bi-stoPtion in the morphology ofthe EaTth. tn~tliabout: (1) What killed dinosaurs at the end-Cretaceous? If we imagine a scenario of the post 65 Ma era, it is possible and (2) Had the mass extinction during the geological history that the intelligent being of the future era may find these been abrupt or is a gradual process? The objective of this changes incorporated in a thin sedimentary layer with no paper is an attempt on the basis of data collected fiom lateral continuity, and may fall into the trap of interprcting the Barmer Basin, Rajasthan, to find a plausible answer to tens of thousand years as a very very small time period. It is these two questions. to be noted that the enormity of dinosaurs must have caused The palaeontological analysis done by Sepkoski (I 992) extinction of many of the species of the Cretaceous Period. reveals that the Earth has suffered five major mass Though, final blow responsible for complete deterioration extinctions during its history: during Late Ordovician, the in the environment could be an impact that led to the death Devonian, the Pertnian, the Triassic and the Cretaceous. It of dinosaurs. is generally believed that the species become extinct when The Banner Basin is a narrow N-S trending graben. Its their rate of adaptation is not able to compete with the western margin is defined by a NNW-SSE trending fault environrnei~talstress. The Earth has suffered many such exposed in the west of Barrner town where clastics of the episodes when its environment got highly deteriorated and Banner Hill Formation are down faulted against Malani became unsuitable for the then thriving species. The records Rhyolite. Its southern extension is restricted by a NE-S W of such events are often preserved in the sedimentary trending fault scarp exposed near Sarnu. A ridge exposing deposits of the Earth. The geological boundaries in the Fatehgarh Fonnation underlain by Lathi Formation shows stratigraphical scale are therefore,rnanifestations of the its northern limit while its eastern margin is not observed. physical, cl~emicaland biological changes that Earth suffered The sediments of the Barmer Basin are classified as pre- during its long l~istory.If we take into consideration a recent rift, syn-rift and post-rift that deposited on tlze Late trend in the extinction of the species we find that there has Proterozoic Malani Igneous Suite (Sisodia and Singh, 2000). been a rapid annihilation of many of the species in the past The pre-rift sediments are represented by: 1. Randha few hundred years. Thirty of the species became extinct in Formation (Siliceous facies). 2. Birmania Formation the 17" century while forty species lost their existence in (Calcareous facies) and 3. Lathi Formation. The syn-rift the I 81h century. In the 1 gthcentury 100 species were wiped sediments include Banner Hill Formation and Fatchgarh off fiorn the globe and the same number of species vanished Formation. The Fatehgarh Fonnation shows a mixed sand in the 2oth century. The culprit responsible for this and mud tidal flat environment, it comprises besides other catastrophe is often interpreted as 'Man'.This inay partly sediments a phosphorite bed with iiiicro vertebrate fossils be true as man's activities towards a developed world are of Late Cretaceous age such as lgdabatis along with forms resulting in a severe environn~entalstress leading to inability of Sernionodon/id, Lnpisosteum, Enchodontid (Mathur et for many of the species to adapt to the recurring changes. al. 2005). A thin unit called Siliceous Earth overlies Many of the scientists have shown their apprehension that Fatehgarh Formation. Siliceous Earth is basically a volcanic this is a period of sixth major inass extinction. One of the ash that represents a sequential time deposit accumulated prime reasons for this extinction is probably perturbation in over a short span of time close to the Cretaceous- the delicate balance of nitrogen (78%), oxygen (2 1%) and Tertiary Boundary event (Sisodia et al. 2005). Most of the other gases (1%) in the atmosphere. ~llthese changes are Barrner Basin has been filled up with post-rift sediments getting recorded in the Earth in the form of fossils, chemical constituting the Mataji-ka-dungar Formation and * Lecture delivered at the Geological Socieq ofIndia on 26 April 2006 at Bungalore JOUR.GEOL.SOC.INDIA, V01,.67, JUNE 2006 NOTES 829 Akli Formation. Mataji-ka-dungar Formation is a pro-deltaic, It is to be noted that at the terminal Cretaceous, one large delta slope/delta mouth deposition. Akli Formation impact at Chicxufub responsible for the extinction of comprises bentonite and lignite representing low energy dinosaurs is well documented (Hildebrand et al. 1991). Its shallow basinal sedimentation. Lignites developed in ejeta however, is not expected to reach India according to protected lagoons within this setting. The palynological the fallout model of Alvarez (1996). One possibility analysis of shales and lignites of Akli Formation yielded therefore, for this material to be in the Barmer Basin is different palynomorphs of Middle to Late Palaeocene age that it can be a post-impact storm surged material flooded such as Da~tdotiaspora,Proxapertites, Spi~zizo~zscolpites onto the coastal zones of Indian Peninsula, which at the and Matu~ronznd~~iasulcites(Tripathi et al. 2003). The above time of Chicxulub impact was placed totally isolated in the described stratigraphy shows that the Barmer Basin Indian Ocean. The discovery of iridium anomaly and epitomizes a record 'of continuous deposition from Late impactites at Urn Sohrygkew, Meghalaya (Bhandari et al. Jurassic to Early Eocene and hence, it can be testimony to 1987) and at Anjar, Kutch (B handari et al. 1996) however the event at the terminal Cretaceous responsible for the does not strongly support this possibility and necessitates extinction of dinosaurs. rethinking for a plausible but judicious answer to the K/T A thin layer overlying phosphorite bed of the Fatehgarh extinction. May be! We should look for another crater in Formation (Late Cretaceous in age) yielded unusual the Indian Peninsula. Shiva Crater in offshore western India sediments that include: micro spherules consisting of opaque has already been proposed (Chatterjee and ~udra,%996). rim enclosing glassy interior; highly fractured quartz; quartz At the same time it is also necessary to note that since grains showing planar fractures; glassy balls; highly Chicxulub did not trigger Deccan Volcanism (B handari et magnetic fine dust and micro breccia with flow texture and al. 1995) there is a leeway that this - another crater may be constituted of opaque iron glass, siliceous glass, spherules a candidate that triggered Deccan Volcanism; and both and high1y fractured quartz fragments (Mathur et at. 2005). catastrophes together changed the history of life on the This type of sediments are mostly a product of impact origin. Earth ! ! References ALVARE,W. (I 996) Trajectories ofballistic ejecta from die Chicxulub MATHUR,S.C., GAUR,S.D., LOYAL,R.S., TRIPATHI,A. ad SISODIA, Crater. Geol. Soc. Arner. Special Paper 307, pp. 141- 1 50. M.S. (2005) Spherules from the Latc Cretaceous phosphorite BI-IANDARI,N., SHUKLA, P.N. and PANDEY,J. (1987) Iridium of the Fatehgarh Formation, Barrner Basin, India. Gondwana ehichment at Cretaceous-Tertiary boundary in Meghalaya. Res., v.8, pp.579-584. Curr. Sci., v 56, pp. 1003- 1005. SEPKOSKI,J.J., Jr. (1 992) Tcn years in the Library: New data BHANDARI,N., SHUKLA, PN., GWEVARIYA, Z.G. and SUNDARAM,S.M. confirm paleontological patterns. Paleobiology, v.19, pp.43- (1995) Impact did not trigger Deccan volcanism: Evidences 5 1. from Anjar K/Tboundary intertrappean sediments. Geophys. SISODIA,M.S. and SINGH,U.K. (2000) Depositional environments Res. Lett. v.22, pp.433-436. and hydrocarbon prospects of Barmer Basin, Rajasthan, India. BHANDARI,N., SHUKLA, P.N., GHEVARIYA,Z.G. and SUNDARAM,S.M. Nafta, v.5 I, pp.309-326. (1 996) K/Tboundary layer in Deccan intertrappeans at Anjar, SISODIA,M.S., SINGH,U.K., LASHKARI, G., SHUKLA,P.N., SHUKLA, Kutch. Geol. Soc. Amer. Spl. Paper 307, pp.417-424. A. and BHANDARI,N. (2005). Mineralogy and trace element CHAITERJEE,S. and RUDRA,D.K. ( 1996) KTevents in India: Impact, chemistry of the Siliceous Earth of Barmer Basin, Rajasthan: rifting, volcanism, and dinosaur extinction. ~'emoir, Evidences for a volcanic origin. Jour. Earth System Science, Queensland Museum, v.39, pp.489-532. v.114, pp.111-124. HILDEBRAND,A.R., PEMFIELD,G.T., CRINGE,D.A., PKLKINGTON, M., TRIPATHI,S.K.M., SINGH,U.K. and SISOD~A,M.S. (2003) CAMARGO,A., JACOBSON,S.B. and BOYNTON,W.V. (1991) Palynological investigation and environmental interpretation Chicxulub Crater; A possible Cretaceous-Tertiary of Late Palaeocene sediments from Barmer Basin, Western boindary impact crater on the Yucatan Peninsula, Mexico. Rajasthan, India. Palaeobotanist, v.52, pp.87-95. Geology, v. 19, pp.867-87 1. JOUR.GEOL.SOC.INDIA,VOL.67, JUNE 2006 .