Rebonds: Structural Affordances, Negotiation, and Creation

This paper presents a comparative recording analysis of the seminal work for solo percussion Rebonds (Iannis Xenakis, 1989), in order to demonstrate how performances of a musical work can reveal—or even create—aspects of musical structure that score-centered analysis cannot illuminate. In doing so I engage with the following questions. What does a pluralistic, dynamic conception of structure look like for Rebonds? How do interpretive decisions recast performers as agents of musical structure? When performances diverge from the score in the omission of notes, the softening of accents, the insertion of dramatic tempo changes, or the altering of entire passages, do conventions that arise out of those performance practices become part of the structural fabric of the work? Are these conventions thus part of the Rebonds “text”?

Thematic interpretation of heliborne magnetic data for delineation of concealed regional structural fabric in the Narnaul-Palsana tract, North Delhi Fold Belt, India

The North Delhi Fold Belt (NDFB) exposure of the Delhi Supergroup of rocks is significant for its structurally controlled uranium mineralization. The Narnaul-Palsana tract within the Khetri subbasin of the NDFB comprises the arenaceous Alwar and argillaceous Ajabgarh Groups of the Delhi Supergroup. The metasedimentary sequence has been subjected to polyphase deformation and igneous intrusion. We used heliborne magnetic data to enhance our geologic understanding of the area. Total magnetic intensity data are gridded and enhanced to resolve the magnetic anomalies. The regional magnetic signature reveals a deep-seated fracture. Varying concentrations of magnetic minerals in different lithologies are reflected in the magnetic response and provide clues to the formational trends. Trend lines and breaks are extracted from the magnetic signature. Thematic analysis of trend lines reveals formational trends that indicate an antiformal and synformal fold pattern in different sectors of the study area. The spatial correlation of the fold patterns is used to decipher the tectonic sequence. Superimposition of antiformal folding over earlier antiform-synform structure and displacement due to later faulting is inferred. Magnetic data analysis is used as a tool to unravel the regional structural fabric of the area that is widely concealed below soil cover.

The structural evolution of the Albula Pass region, Graubünden, eastern Switzerland: the origin of the various vergences in the structure of the Alps

The Albula Pass region lies between the Lower Austroalpine Err Nappe and the Middle Austroalpine Silvretta Nappe. They will be treated here as the frame of the non- to gently metamorphic sedimentary units between the two during the Alpide times. Sedimentation started on a metamorphic Hercynian basement during the latest Carboniferous(?) and continued into the Permian. Then a sequence from the Alpine Buntsandstein to the medial Jurassic to early Cretaceous Aptychenkalk (=Maiolica) and radiolarites were deposited in an environment of rifting and subsidence. The succeeding Palombini clastics were laid down after the Aptychenkalk and mark the onset of shortening in the Alpine realm. The initial structures that formed were at least two north-dipping normal faults which formed before the deposition of the Jurassic sedimentary rocks. When shortening set in, the first structure that came into being was the south-vergent Elalbula Nappe, bending the normal faults into close antiforms. It became further dismembered into two pieces creating parts of the future Ela and Albula nappes in the Albula region. This motion was later reversed, when the entire ensemble became bulldozed by the immense body of the Silvretta Nappe along numerous, closely spaced thrust faults, some of which only very locally followed horizontal bits of the old normal faults, but in principle they determined their own course. No evidence for westerly motion could be identified, although microstructures in the structural fabric were not studied. The reason for this may be the pre-orogenic fabric in the bounding tectonic units.