IMPACT PROCESSES ARE AN IMPORTANT PART OF THE EARLY HISTORY OF THE SOLAR SYSTEM AND THE RESULTING SHOCK EFFECTS IN METEORITES PROVIDE A RECORD OF IMPACTS AND SOLAR SYSTEM DYNAMICS (SCOTT 2002; CONSOLMAGNO AND BRITT 2004). HOWEVER MOST OF WHAT WE HAVE LEARNED ABOUT SHOCK METAMORPHISM IN ORDINARY CHONDRITES AND MARTIAN METEORITES REPRESENTS RELATIVELY LATE SOLAR SYSTEM IMPACT EVENTS (SWINDLE ET AL. 2014; MOSER ET AL. 2013). OUR KNOWLEDGE OF HIGHLY SHOCKED METEORITES IS STRONGLY INFLUENCED BY THE LARGE QUANTITY OF SHOCKED L CHONDRITES WHICH WERE PREDOMINANTLY SHOCKED IN A LARGE IMPACT EVENT AT 470 MA (TURNER 1969; BOGARD ET AL. 1976; KOROCHANTSEVA ET AL. 2007; HECK ET AL. 2008; WEIRICH ET AL. 2012). AS A RESULT WE KNOW RELATIVELY LITTLE ABOUT SHOCK EFFECTS FROM SOLAR SYSTEM IMPACT EVENTS OLDER THAN 4150 MA. 40AR/39AR AGES OF IMPACTS IN ORDINARY CHONDRITES (TURNER 1969; BOGARD ET AL. 1976; TURNER 1978; BOGARD 1995; KOROCHANTSEVA ET AL. 2007; SWINDLE ET AL. 2009; SWINDLE ET AL. 2014) DEMONSTRATE THAT MANY CHONDRITES HAVE EXPERIENCED IMPACT EVENTS>4150 MA. THE GOAL OF THE PROPOSED STUDY IS TO INVESTIGATE SHOCK EFFECTS SHOCK CONDITIONS ANNEALING AND IMPACT AGES IN THE EARLIEST SHOCKS RECORDED IN ORDINARY CHONDRITES TO BETTER UNDERSTAND IMPACT PROCESSES IN THE FIRST 400 MA OF SOLAR SYSTEM HISTORY. SHOCK EFFECTS IN METEORITES ARE WELL PRESERVED IN RAPIDLY QUENCHED SAMPLES BUT THEY CAN BE PARTIALLY OR COMPLETELY ANNEALED AFTER SHOCK OR DURING THERMAL METAMORPHISM. DEFORMATION AND TRANSFORMATIONAL MICROSTRUCTURES THAT SURVIVE CAN BE USED TO INVESTIGATE BOTH SHOCK AND POST-SHOCK PROCESSES. 40AR/39AR AGES PROVIDE A CHRONOLOGICAL HISTORY OF IMPACT EVENTS IN METEORITES IN ADDITION TO CONSTRAINTS ON TIME-TEMPERATURE HISTORIES (SWINDLE ET AL. 2014). WE PROPOSE TO PERFORM DETAILED MINERALOGICAL AND MICROSTRUCTURAL ANALYSIS OF CHONDRITES SHOCKED IN THE OLDEST POST-ACCRETION IMPACT PROCESSES. WE WILL USE POLARIZED-LIGHT MICROSCOPY TO CLASSIFY THE SHOCK STAGE AND MAP OUT LOCAL SHOCK MELTING AND TRANSFORMATION IN SAMPLES THAT HAVE 40AR/39AR AGES>4150 MA. WE WILL USE RAMAN SPECTROSCOPY AND SYNCHROTRON X-RAY DIFFRACTION TO IDENTIFY HIGH-PRESSURE MINERALS FORMED BY SHOCK. WE WILL USE BACKSCATTERED ELECTRON IMAGING AND ENERGY DISPERSIVE ANALYSIS WITH OUR FIELD-EMISSION SEMS TO CHARACTERIZE NANO-SCALE DEFORMATION MELTING AND REACTION MICROSTRUCTURES. WE WILL USE THE FOCUSED-ION-BEAM LIFT-OUT TECHNIQUE TO PREPARE SAMPLES FOR ANALYTICAL TRANSMISSION ELECTRON MICROSCOPY (TEM). TEM WILL BE USED TO IDENTIFY AND CHARACTERIZE NANO-MINERALOGY NANOMETER-SCALE REACTION STRUCTURES DEFORMATION MICROSTRUCTURES AND ANNEALING EFFECTS. FINALLY WE WILL USE 40AR/39AR DATING TO REFINE THE AGES OF SOME OF THE OLDEST SHOCKED SAMPLES TO BETTER EVALUATE THE TIMING OF EARLY IMPACT PROCESSES. THESE DATA COMBINED WITH PUBLISHED 40AR/39AR AGE DATA WILL BE USED TO PROVIDE A DETAILED RECORD OF SHOCK EFFECTS SHOCK CONDITIONS AND POST-SHOCK ANNEALING IN THE OLDEST SHOCKED MATERIALS IN THE SOLAR SYSTEM. THIS DATA WILL PROVIDE NEW INSIGHTS INTO THE ROLE OF IMPACTS AND SHOCK IN THE METAMORPHISM OF ASTEROIDS IN THE EARLY HISTORY OF OUR SOLAR SYSTEM.