Preliminary study of the gravity field of the southern Urals along the URSEIS '95 seismic profile

Role of a phase: Change Moho in stabilization and preservation of the Southern Uralide orogen, Russia

“…The flexural model proposed by Kruse and McNutt [1988] argued for the presence of a subsurface crustal load to account for the subdued (-50 mgal; Figure 2c) negative Bouguer gravity anomaly above the central part of the orogen. More recently, Doring and Gotze [1999] modeled the gravity field across the URSElS profile (Figure 2c), and they suggested the presence of high density rocks (3.25-3.45 gicm 3 ; Figure 2c) within the root. Therefore, this discrepancy of a lack of a significant negative gravity anomaly across a preserved, non-extended orogen, could be accounted for, if in fact, the original root has been transformed into a higher density eclogite consistent with the model proposed in this paper and the densities derived from the gravity modeling [Doring and Gotze, 1999; Figure 2c).…”

“…More recently, Doring and Gotze [1999] modeled the gravity field across the URSElS profile (Figure 2c), and they suggested the presence of high density rocks (3.25-3.45 gicm 3 ; Figure 2c) within the root. Therefore, this discrepancy of a lack of a significant negative gravity anomaly across a preserved, non-extended orogen, could be accounted for, if in fact, the original root has been transformed into a higher density eclogite consistent with the model proposed in this paper and the densities derived from the gravity modeling [Doring and Gotze, 1999; Figure 2c). The Magnitogorsk volcanic arc in the hanging wall of the Main Uralian fault, with high density (~3.0 g/cm 3 ) rocks, appears to account for the short wavelength local Bouguer gravity maximum (~1 0 mgal) across the axis of the orogen [Doring and Gotze, 1999].…”

“…Numbers on the top of eross-section represent cooling ages from zircon and apatite fission-track data after Seward et ai. (1997); (c) Gravity model along the URSEIS profile showing crustal densities and their calculated versus measured Bouguer gravity effect (adapted from Doring and Gotze, 1999). craton, and Kazakhstan [Hamilton, 1970; hinterland [e.g., Rodgers, 1990]. However, fundamental et aI., 1984; Zonenshain et aI., 1990;Puchkov, 1996].…”

“…The presence of a Uralian crustal root has long been a subject of controversy since the crust appears to be much thicker than required for the compensation of the subdued topography [Kruise and McNutt, 1988;Doring and GOtze, 1999]. The URSEIS (Urals Seismic Experiment and Integrated Studies) deep seismic profile across the Southern Uralides displays a highly reflective subhorizontal Moho reflection at -42-45 km depth beneath the Uralian foreland and hinterland (Figure 2a).…”

Structural framework of the Bashkirian anticlinorium, SW Urals

“…Perez -Estaun et al (1997) have pointed out the importance of Middle and Upper Riphean aulacogen structures (Kaltasin aulacogen, Sernovodsk-Abdulino aulacogen) which strike in a high angle to the Uralian grain into the orogen. Whereas the southern aulacogen has been interpreted to form a lateral ramp terminating the BMA to the south , the NW/SE-trending Kaltasin aulacogen strikes according to gravimetric and magnetic maps into the investigated area (Shapiro et al 1997;Döring et al 1997). The Karatau fault represents a prominent feature which appears to be connected with the former margins of the aulacogen (Puchkov 1997).…”